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397 results on '"R. Maingi"'

1. Initial design concepts for solid boron injection in ITER

Author

J.A. Snipes, L.R. Baylor, A. Bortolon, F. Effenberg, E.P. Gilson, A. Loarte, R. Lunsford, R. Maingi, S. Meitner, F. Nespoli, S. Maruyama, A. Nagy, Z. Sun, J. Ulreich, and T. Wauters

Subjects
ITER, Wall conditioning, Boron injection, Boronization, Nuclear engineering. Atomic power, TK9001-9401
Abstract

As part of ITER’s consideration to change its first wall material from beryllium to tungsten, the ITER Organization has proposed studying the feasibility of real-time solid boron injection (SBI) into the plasma to coat the walls and divertor to supplement glow discharge boronization (GDB) [1]. Boron deposits getter oxygen and reduce sputtering of tungsten from plasma facing components (PFCs). Particularly in areas with significant plasma wall interactions, boron coatings are expected to be short-lived under high performance plasma conditions. The proposed SBI system aims to maintain boron layers in these areas to avoid excessive radiation from tungsten in the plasma as a risk mitigation to ensure ITER will be able to reach and sustain Q = 10 conditions. The system will be used sparingly, as redeposition of boron can lead to significant tritium retention, which must be minimized in ITER to comply with nuclear safety concerns. SBI is proposed to limit and precisely control the amount of boron injected in real-time during plasma operation. Here, some of the design requirements and initial concepts for an SBI system in ITER are presented based on previous results carried out with SBI systems on a number of tokamaks and stellarators around the world [2–18].Previous results using SBI systems installed by PPPL have injected boron particles from 5 µm–2 mm diameter at calibrated rates of 2–200 mg/s in real-time during plasma operation on AUG [4], DIII-D [5], EAST [6], KSTAR [7], LHD [8], TFTR [9], WEST [10], and W7-X [11,12], leading to improved wall conditions with reduced plasma impurity concentrations and radiated power and improved plasma performance. The boron is ionized in the plasma edge and then deposited on plasma-wetted surfaces. On AUG [4], EAST [6] and WEST [10] reduced tungsten sputtering sources were observed following several discharges with SBI. Extrapolation of these SBI results are presented to estimate the amount of boron needed for wall conditioning in ITER. Real-time SBI control requirements and plasma operation scenarios for ITER are also described.

Published
2024
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2. In search of X-point radiator regime features in NSTX and DIII-D discharges with the snowflake divertor

Author

V.A. Soukhanovskii, S.L. Allen, M.E. Fenstermacher, C.J. Lasnier, A.G. McLean, F. Scotti, E. Kolemen, A. Diallo, S. Gerhardt, S. Kaye, B.P. LeBlanc, R. Maingi, J.E. Menard, R. Raman, A.W. Hyatt, A.W. Leonard, and T.H. Osborne

Subjects
Divertor, Snowflake, XPR, MARFE, Confinement, Nuclear engineering. Atomic power, TK9001-9401
Abstract

Experimental data from NSTX and DIII-D discharges with the snowflake (SF) divertor configurations are analyzed toward the development of the X-point radiator (XPR) concept. The XPR divertor regime was recently realized in standard divertor configurations in several tokamaks The SF divertor configuration, with an additional poloidal field null nearby the main X-point, could provide additional benefits for the XPR: a higher flux expansion inside the separatrix and an extended private flux region. This may lead to lower temperatures and higher neutral and electron densities, which are thought to be essential for XPR stability, initiation, and impurity containment. In this work, 4 MW NBI-heated H-mode NSTX discharges and 3–5 MW NBI-heated H-mode DIII-D discharges with SF-minus and SF-plus divertors, with the ion B×∇B drift toward the lower divertor, with and without D2 and CD4 seeding, were analyzed. Many experimental XPR features were found, including good or slightly degraded H-mode confinement, significant ELM size reduction, nearly complete divertor power detachment and a significant divertor radiated power loss. However, evidence of the XPR extending into the confined region was inconclusive in the NSTX tokamak, while in DIII-D, a number of discharges demonstrated a stable MARFE-like structure inside the separatrix over a wide operating space. The present analysis supports the SF divertor as a good candidate for further XPR scenario development in DIII-D and NSTX-U.

Published
2024
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3. Overview of ASDEX upgrade results in view of ITER and DEMO

Author

H. Zohm, E. Alessi, C. Angioni, N. Arden, V. Artigues, M. Astrain, O. Asunta, M. Balden, V. Bandaru, A. Banon Navarro, M. Bauer, A. Bergmann, M. Bergmann, J. Bernardo, M. Bernert, A. Biancalani, R. Bielajew, R. Bilato, G. Birkenmeier, T. Blanken, V. Bobkov, A. Bock, L. Bock, T. Body, T. Bolzonella, N. Bonanomi, A. Bortolon, B. Böswirth, C. Bottereau, A. Bottino, H. van den Brand, M. Brenzke, S. Brezinsek, D. Brida, F. Brochard, J. Buchanan, A. Buhler, A. Burckhart, Y. Camenen, B. Cannas, P. Cano Megías, D. Carlton, M. Carr, P. Carvalho, C. Castaldo, A. Castillo Castillo, A. Cathey, M. Cavedon, C. Cazzaniga, C. Challis, A. Chankin, A. Chomiczewska, C. Cianfarani, F. Clairet, S. Coda, R. Coelho, J.W. Coenen, L. Colas, G. Conway, S. Costea, D. Coster, T. Cote, A.J. Creely, G. Croci, D.J. Cruz Zabala, G. Cseh, I. Cziegler, O. D’Arcangelo, A. Dal Molin, P. David, C. Day, M. de Baar, P. de Marné, R. Delogu, P. Denner, A. Di Siena, M. Dibon, J.J. Dominguez-Palacios Durán, D. Dunai, M. Dreval, M. Dunne, B.P. Duval, R. Dux, T. Eich, S. Elgeti, A. Encheva, B. Esposito, E. Fable, M. Faitsch, D. Fajardo Jimenez, U. Fantz, M. Farnik, H. Faugel, F. Felici, O. Ficker, A. Figueredo, R. Fischer, O. Ford, L. Frassinetti, M. Fröschle, G. Fuchert, J.C. Fuchs, H. Fünfgelder, S. Futatani, K. Galazka, J. Galdon-Quiroga, D. Gallart Escolà, A. Gallo, Y. Gao, S. Garavaglia, M. Garcia Muñoz, B. Geiger, L. Giannone, S. Gibson, L. Gil, E. Giovannozzi, I. Girka, O. Girka, T. Gleiter, S. Glöggler, M. Gobbin, J.C. Gonzalez, J. Gonzalez Martin, T. Goodman, G. Gorini, T. Görler, D. Gradic, G. Granucci, A. Gräter, G. Grenfell, H. Greuner, M. Griener, M. Groth, O. Grover, A. Gude, L. Guimarais, S. Günter, D. Hachmeister, A.H. Hakola, C. Ham, T. Happel, N. den Harder, G. Harrer, J. Harrison, V. Hauer, T. Hayward-Schneider, B. Heinemann, P. Heinrich, T. Hellsten, S. Henderson, P. Hennequin, M. Herschel, S. Heuraux, A. Herrmann, E. Heyn, F. Hitzler, J. Hobirk, K. Höfler, S. Hörmann, J.H. Holm, M. Hölzl, C. Hopf, L. Horvath, T. Höschen, A. Houben, A. Hubbard, A. Huber, K. Hunger, V. Igochine, M. Iliasova, J. Illerhaus, K. Insulander Björk, C. Ionita-Schrittwieser, I. Ivanova-Stanik, S. Jachmich, W. Jacob, N. Jaksic, A. Jansen van Vuuren, F. Jaulmes, F. Jenko, T. Jensen, E. Joffrin, A. Kallenbach, J. Kalis, A. Kappatou, J. Karhunen, C.-P. Käsemann, S. Kasilov, Y. Kazakov, A. Kendl, W. Kernbichler, E. Khilkevitch, M. Kircher, A. Kirk, S. Kjer Hansen, V. Klevarova, F. Klossek, G. Kocsis, M. Koleva, M. Komm, M. Kong, A. Krämer-Flecken, M. Krause, I. Krebs, A. Kreuzeder, K. Krieger, O. Kudlacek, D. Kulla, T. Kurki-Suonio, B. Kurzan, B. Labit, K. Lackner, F. Laggner, A. Lahtinen, P. Lainer, P.T. Lang, P. Lauber, M. Lehnen, L. Leppin, E. Lerche, N. Leuthold, L. Li, J. Likonen, O. Linder, H. Lindl, B. Lipschultz, Y. Liu, Z. Lu, T. Luda Di Cortemiglia, N.C. Luhmann, T. Lunt, A. Lyssoivan, T. Maceina, J. Madsen, A. Magnanimo, H. Maier, J. Mailloux, R. Maingi, O. Maj, E. Maljaars, V. Maquet, A. Mancini, A. Manhard, P. Mantica, M. Mantsinen, P. Manz, M. Maraschek, C. Marchetto, M. Markl, L. Marrelli, P. Martin, F. Matos, M. Mayer, P.J. McCarthy, R. McDermott, G. Meng, R. Merkel, A. Merle, H. Meyer, M. Michelini, D. Milanesio, V. Mitterauer, P. Molina Cabrera, M. Muraca, F. Nabais, V. Naulin, R. Nazikian, R.D. Nem, R. Neu, A.H. Nielsen, S.K. Nielsen, T. Nishizawa, M. Nocente, I. Novikau, S. Nowak, R. Ochoukov, J. Olsen, P. Oyola, O. Pan, G. Papp, A. Pau, G. Pautasso, C. Paz-Soldan, M. Peglau, E. Peluso, P. Petersson, C. Piron, U. Plank, B. Plaum, B. Plöckl, V. Plyusnin, G. Pokol, E. Poli, A. Popa, L. Porte, J. Puchmayr, T. Pütterich, L. Radovanovic, M. Ramisch, J. Rasmussen, G. Ratta, S. Ratynskaia, G. Raupp, A. Redl, D. Réfy, M. Reich, F. Reimold, D. Reiser, M. Reisner, D. Reiter, B. Rettino, T. Ribeiro, D. Ricci, R. Riedl, J. Riesch, J.F. Rivero Rodriguez, G. Rocchi, P. Rodriguez-Fernandez, V. Rohde, G. Ronchi, M. Rott, M. Rubel, D.A. Ryan, F. Ryter, S. Saarelma, M. Salewski, A. Salmi, O. Samoylov, L. Sanchis Sanchez, J. Santos, O. Sauter, G. Schall, A. Schlüter, J. Scholte, K. Schmid, O. Schmitz, P.A. Schneider, R. Schrittwieser, M. Schubert, C. Schuster, N. Schwarz, T. Schwarz-Selinger, J. Schweinzer, F. Sciortino, O. Seibold-Benjak, A. Shabbir, A. Shalpegin, S. Sharapov, U. Sheikh, A. Shevelev, G. Sias, M. Siccinio, B. Sieglin, A. Sigalov, A. Silva, C. Silva, D. Silvagni, J. Simpson, S. Sipilä, A. Snicker, E. Solano, C. Sommariva, C. Sozzi, M. Spacek, G. Spizzo, M. Spolaore, A. Stegmeir, M. Stejner, D. Stieglitz, J. Stober, U. Stroth, E. Strumberger, G. Suarez Lopez, W. Suttrop, T. Szepesi, B. Tál, T. Tala, W. Tang, G. Tardini, M. Tardocchi, D. Terranova, M. Teschke, E. Thorén, W. Tierens, D. Told, W. Treutterer, G. Trevisan, M. Tripský, P. Ulbl, G. Urbanczyk, M. Usoltseva, M. Valisa, M. Valovic, S. van Mulders, M. van Zeeland, F. Vannini, B. Vanovac, P. Varela, S. Varoutis, T. Verdier, G. Verdoolaege, N. Vianello, J. Vicente, T. Vierle, E. Viezzer, I. Voitsekhovitch, U. von Toussaint, D. Wagner, X. Wang, M. Weiland, D. Wendler, A.E. White, M. Willensdorfer, B. Wiringer, M. Wischmeier, R. Wolf, E. Wolfrum, Q. Yang, C. Yoo, Q. Yu, R. Zagórski, I. Zammuto, T. Zehetbauer, W. Zhang, W. Zholobenko, A. Zibrov, M. Zilker, C.F.B. Zimmermann, A. Zito, S. Zoletnik, the EUROfusion Tokamak Exploitation Team, and the ASDEX Upgrade Team

Subjects
tokamak, MHD stability, transport modelling, radiative exhaust, disruption physics, ELM free scenarios, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Experiments on ASDEX Upgrade (AUG) in 2021 and 2022 have addressed a number of critical issues for ITER and EU DEMO. A major objective of the AUG programme is to shed light on the underlying physics of confinement, stability, and plasma exhaust in order to allow reliable extrapolation of results obtained on present day machines to these reactor-grade devices. Concerning pedestal physics, the mitigation of edge localised modes (ELMs) using resonant magnetic perturbations (RMPs) was found to be consistent with a reduction of the linear peeling-ballooning stability threshold due to the helical deformation of the plasma. Conversely, ELM suppression by RMPs is ascribed to an increased pedestal transport that keeps the plasma away from this boundary. Candidates for this increased transport are locally enhanced turbulence and a locked magnetic island in the pedestal. The enhanced D-alpha (EDA) and quasi-continuous exhaust (QCE) regimes have been established as promising ELM-free scenarios. Here, the pressure gradient at the foot of the H-mode pedestal is reduced by a quasi-coherent mode, consistent with violation of the high-n ballooning mode stability limit there. This is suggestive that the EDA and QCE regimes have a common underlying physics origin. In the area of transport physics, full radius models for both L- and H-modes have been developed. These models predict energy confinement in AUG better than the commonly used global scaling laws, representing a large step towards the goal of predictive capability. A new momentum transport analysis framework has been developed that provides access to the intrinsic torque in the plasma core. In the field of exhaust, the X-Point Radiator (XPR), a cold and dense plasma region on closed flux surfaces close to the X-point, was described by an analytical model that provides an understanding of its formation as well as its stability, i.e., the conditions under which it transitions into a deleterious MARFE with the potential to result in a disruptive termination. With the XPR close to the divertor target, a new detached divertor concept, the compact radiative divertor, was developed. Here, the exhaust power is radiated before reaching the target, allowing close proximity of the X-point to the target. No limitations by the shallow field line angle due to the large flux expansion were observed, and sufficient compression of neutral density was demonstrated. With respect to the pumping of non-recycling impurities, the divertor enrichment was found to mainly depend on the ionisation energy of the impurity under consideration. In the area of MHD physics, analysis of the hot plasma core motion in sawtooth crashes showed good agreement with nonlinear 2-fluid simulations. This indicates that the fast reconnection observed in these events is adequately described including the pressure gradient and the electron inertia in the parallel Ohm’s law. Concerning disruption physics, a shattered pellet injection system was installed in collaboration with the ITER International Organisation. Thanks to the ability to vary the shard size distribution independently of the injection velocity, as well as its impurity admixture, it was possible to tailor the current quench rate, which is an important requirement for future large devices such as ITER. Progress was also made modelling the force reduction of VDEs induced by massive gas injection on AUG. The H-mode density limit was characterised in terms of safe operational space with a newly developed active feedback control method that allowed the stability boundary to be probed several times within a single discharge without inducing a disruptive termination. Regarding integrated operation scenarios, the role of density peaking in the confinement of the ITER baseline scenario (high plasma current) was clarified. The usual energy confinement scaling ITER98( p,y ) does not capture this effect, but the more recent H20 scaling does, highlighting again the importance of developing adequate physics based models. Advanced tokamak scenarios, aiming at large non-inductive current fraction due to non-standard profiles of the safety factor in combination with high normalised plasma pressure were studied with a focus on their access conditions. A method to guide the approach of the targeted safety factor profiles was developed, and the conditions for achieving good confinement were clarified. Based on this, two types of advanced scenarios (‘hybrid’ and ‘elevated’ q -profile) were established on AUG and characterised concerning their plasma performance.

Published
2024
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4. DIII-D research to provide solutions for ITER and fusion energy

Author

C.T. Holcomb, for the DIII-D Team:, J. Abbate, A. Abe, A. Abrams, P. Adebayo-Ige, S. Agabian, S. Ahmed, N. Aiba, N. Akcay, T. Akiyama, R. Albosta, P. Aleynikov, S. Allen, H. Anand, J. Anderson, Y. Andrew, M. Ashburn, A. Ashourvan, M. Austin, G. Avdeeva, D. Ayala, M. Ayub, E. Bagdy, S. Banerjee, K. Barada, L. Bardoczi, O. Bardsley, J. Barr, E. Bass, A. Battey, Z. Bayler, L. Baylor, T. Bechtel, M. Beidler, E. Belli, T. Benedett, Z. Bergstrom, M. Berkel, T. Bernard, N. Bertelli, R. Bielajew, G. Bodner, J. Boedo, R. Boivin, T. Bolzonella, P. Bonoli, A. Bortolon, S. Bose, M. Boyer, W. Boyes, L. Bradley, R. Brambila, A. Braun, D. Brennan, S. Bringuier, L. Brodsky, M. Brookman, J. Brooks, D. Brower, W. Brown, J. Buck, S. Buczek, D. Burgess, M. Burke, K. Burrell, J. Butt, R. Buttery, I. Bykov, P. Byrne, A. Cacheris, K. Callahan, J. Callen, D. Campbell, J. Candy, J. Canik, L. Cappelli, T. Carlstrom, R. Carr, W. Carrig, B. Carter, T. Carter, I. Carvalho, W. Cary, L. Casali, L. Ceelen, M. Cengher, M. Cha, R. Chaban, V. Chan, B. Chapman, I. Char, J. Chen, R. Chen, X. Chen, Y. Chen, J. Chiriboga, E. Cho, G. Choi, W. Choi, H. Choudhury, S. Chowdhury, C. Chrystal, Y. Chung, R. Churchill, R. Clark, M. Clement, J. Coburn, S. Coda, R. Coffee, C. Collins, J. Colmenares-Fernandez, W. Conlin, R. Coon, T. Cote, A. Creely, N. Crocker, C. Crowe, B. Crowley, T. Crowley, M. Curie, D. Curreli, A. Dal Molin, J. Damba, E. Dart, A. Dautt-Silva, K. Davda, A. De, N. de Boucaud, Y. de Jong, P. DE VRIES, A. de-Villeroche, G. DeGrandchamp, J. deGrassie, D. Demers, S. Denk, E. DeShazer, S. Di Genova, A. Diallo, A. Dimits, R. Ding, S. Ding, D. Donovan, X. Du, J. Dunsmore, A. Dupuy, J. Duran, A. Dvorak, F. Effenberg, N. Eidietis, D. Elder, D. Eldon, Y. Elsey, D. Ennis, K. Erickson, D. Ernst, M. Fajardo, H. Farre-Kaga, M. Fenstermacher, N. Ferraro, J. Ferron, A. Feyrer, P. Fimognari, R. Finden, D. Finkenthal, R. Fitzpatrick, S. Flanagan, B. Ford, W. Fox, S. Freiberger, L. Fu, K. Gage, V. Gajaraj, I. Garcia, F. Garcia, A. Garcia, M. Garcia Munoz, D. Garnier, A. Garofalo, A. Gattuso, B. Geiger, K. Gentle, Y. Ghai, K. Gill, F. Glass, P. Gohil, X. Gong, J. Gonzalez-Martin, Y. Gorelov, V. Graber, R. Granetz, C. Gray, C. Greenfield, B. Grierson, R. Groebner, W. Grosnickle, M. Groth, S. Gu, H. Guo, J. Guterl, W. Guttenfelder, R. Hager, S. Hahn, M. Halfmoon, J. Hall, V. Hall-Chen, F. Halpern, G. Hammett, X. Han, C. Hansen, E. Hansen, J. Hanson, M. Hanson, A. Harris, R. Harvey, S. Haskey, D. Hatch, W. Hayashi, A. Hayes, W. Heidbrink, J. Herfindal, J. Hicok, E. Hinson, T. Hisakado, C. Holcomb, C. Holland, L. Holland, E. Hollmann, A. Holm, I. Holmes, K. Holtrop, R. Hong, R. Hood, L. Horvath, S. Houshmandyar, N. Howard, E. Howell, W. Hu, Y. Hu, Q. Hu, Y. Huang, J. Huang, A. Huang, A. Hubbard, J. Hughes, D. Humphreys, J. Hurtado, A. Hyatt, K. Imada, V. Izzo, A. Jalalvand, S. Jardin, A. Jarvinen, Y. Jeon, H. Ji, X. Jian, L. Jian, Y. Jiang, C. Johnson, J. Johnson, M. Jones, S. Joung, P. Jouzdani, E. Jung, E. Kallenberg, R. Kalling, D. Kaplan, A. Kaptanoglu, D. Kellman, J. Kennedy, F. Khabanov, J. Kim, H. Kim, E. Kim, S. Kim, K. Kim, C. Kim, T. Kim, J. King, A. Kinsey, D. Kirk, D. Klasing, A. Kleiner, M. Knolker, M. Kochan, B. Koel, J. Koenders, M. Koepke, R. Kolasinski, E. Kolemen, E. Kostadinova, M. Kostuk, G. Kramer, R. Kube, N. Kumar, R. La Haye, F. Laggner, C. Lahban, H. Lan, R. Landry, R. Lantsov, L. Lao, C. Lasnier, C. Lau, R. Leccacorvi, J. Leddy, M. Lee, S. Lee, K. Lee, R. Lee, M. Lehnen, A. Leonard, E. Leppink, M. LeSher, J. Lestz, J. Leuer, N. Leuthold, G. Li, X. Li, Y. Li, L. Li, N. Li, Z. Li, D. Lin, Z. Lin, Y. Lin, E. Linsenmayer, J. Liu, D. Liu, C. Liu, Z. Liu, Y. Liu, A. Loarte-Prieto, S. Loch, L. LoDestro, N. Logan, J. Lohr, J. Lore, U. Losada Rodriguez, J. Loughran, M. Lowell, T. Luce, N. Luhmann, P. Lunia, R. Lunsford, L. Lupin-Jimenez, A. Lvovskiy, B. Lyons, X. Ma, J. MacDonald, T. Macwan, R. Maingi, M. Major, L. Malhotra, M. Margo, C. Marini, A. Marinoni, A. Maris, E. Martin, J. Mateja, R. Mattes, R. Maurizio, D. Mauzey, L. McAllister, G. McArdle, J. McClenaghan, K. McCollam, G. McKee, K. McLaughlin, A. McLean, V. Mehta, E. Meier, S. Meitner, J. Menard, O. Meneghini, G. Merlo, S. Messer, W. Meyer, C. Michael, D. Miller, M. Miller, J. Mitchell, E. Mitra, C. Moeller, M. Mohamed, S. Molesworth, K. Montes, S. Mordijck, S. Morosohk, A. Moser, D. Mueller, S. Munaretto, C. Murphy, C. Muscatello, R. Myers, A. Nagy, D. Nath, M. Navarro, R. Nazikian, T. Neiser, A. Nelson, P. Nesbet, F. Nespoli, P. Nguyen, D. Nguyen, R. Nguyen, J. Nichols, M. Nocente, L. Nuckols, R. Nygren, T. Odstrcil, M. Okabayashi, E. Olofsson, D. Orlov, D. Orozco, N. Osborne, T. Osborne, F. OShea, D. Pace, D. Packard, A. Pajares Martinez, C. Pakosta, C. Pan, M. Pandya, D. Panici, A. Pankin, Y. Park, J. Park, C. Parker, S. Parker, P. Parks, M. Parsons, S. Paruchuri, C. Paz-Soldan, T. Pederson, W. Peebles, B. Penaflor, E. Perez, L. Periasamy, R. Perillo, C. Petty, M. Pharr, D. Pierce, C. Pierren, S. Pierson, A. Pigarov, L. Pigatto, D. Piglowski, S. Pinches, R. Pinsker, R. Pitts, J. Pizzo, M. Podesta, Z. Popovic, M. Porkolab, Q. Pratt, G. Prechel, I. Pusztai, P. Puthan-Naduvakkate, J. Qian, X. Qin, O. Ra, T. Raines, K. Rakers, K. Rath, J. Rauch, C. Rea, R. Reed, A. Reiman, M. Reinke, R. Reksoatmodjo, Q. Ren, J. Ren, Y. Ren, M. Rensink, T. Rhodes, N. Richner, J. Ridzon, G. Riggs, J. Riquezes, P. Rodriguez Fernandez, T. Rognlien, G. Ronchi, L. Rondini, R. Rosati, A. Rosenthal, M. Ross, J. Rost, A. Rothstein, J. Roveto, J. Ruane, D. Rudakov, R. Rupani, G. Rutherford, S. Sabbagh, J. Sachdev, N. Sadeghi, A. Salmi, F. Salvador, B. Sammuli, C. Samuell, A. Sandorfi, C. Sang, D. Santa, J. Sarff, O. Sauter, H. Savelli, C. Schaefer, H. Schamis, J. Schellpfeffer, D. Schissel, L. Schmitz, O. Schmitz, P. Schroeder, K. Schultz, E. Schuster, F. Sciortino, F. Scotti, J. Scoville, A. Seltzman, J. Seo, J. Serrano, I. Sfiligoi, M. Shafer, R. Shapov, H. Shen, N. Shi, D. Shiraki, B. Short, R. Shousha, H. Si, C. Sierra, G. Sinclair, P. Sinha, G. Sips, C. Skinner, T. Slendebroek, J. Slief, R. Smirnov, S. Smith, D. Smith, G. Snoep, P. Snyder, W. Solomon, X. Song, A. Sontag, V. Soukhanovskii, D. Spong, J. Squire, G. Staebler, L. Stagner, T. Stange, P. Stangeby, E. Starling, S. Stewart, T. Stoltzfus-Dueck, S. Storment, E. Strait, D. Su, L. Sugiyama, P. Sun, Y. Sun, X. Sun, C. Sung, W. Suttrop, Y. Suzuki, R. Sweeney, B. Taczak, Y. Takemura, S. Tang, W. Tang, G. Tardini, D. Taussig, K. Teixeira, K. Thackston, D. Thomas, K. Thome, Y. Tinguely, M. Tobin, J. Tooker, A. Torrezan de Sousa, P. Traverso, G. Trevisan, E. Trier, D. Truong, C. Tsui, F. Turco, A. Turnbull, L. Turner, E. Unterberg, B. Van Compernolle, R. van Kampen, M. Van Zeeland, B. Victor, R. Vieira, E. Viezzer, S. Vincena, D. Vollmer, J. Wai, M. Walker, R. Waltz, W. Wampler, L. Wang, Y. Wang, H. Wang, Z. Wang, G. Wang, A. Wang, J. Watkins, M. Watkins, T. Watts, L. Webber, K. Weber, W. Wehner, X. Wei, D. Weisberg, A. Welander, A. Welsh, A. White, R. Wilcox, G. Wilkie, T. Wilks, M. Willensdorfer, H. Wilson, A. Wingen, M. Wu, D. Wu, S. Wukitch, J. Xia, R. Xie, Z. Xing, G. Xu, X. Xu, Z. Yan, X. Yang, L. Yang, S. Yang, J. Yang, M. Yoo, G. YU, J. Yu, A. Zalzali, A. Zamengo, V. Zamkovska, S. Zamperini, K. Zarrabi, E. Zeger, K. Zeller, L. Zeng, X. Zhang, J. Zhang, B. Zhang, B. Zhao, C. Zhao, Y. Zheng, Y. Zhu, J. Zhu, J. Ziegel, J. Zimmerman, and C. Zuniga

Subjects
DIII-D, tokamak, overview, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

The DIII-D tokamak has elucidated crucial physics and developed projectable solutions for ITER and fusion power plants in the key areas of core performance, boundary heat and particle transport, and integrated scenario operation, with closing the core-edge integration knowledge gap being the overarching mission. New experimental validation of high-fidelity, multi-channel, non-linear gyrokinetic turbulent transport models for ITER provides strong confidence it will achieve Q ⩾ 10 operation. Experiments identify options for easing H-mode access in hydrogen, and give new insight into the isotopic dependence of transport and confinement. Analysis of 2,1 islands in unoptimized low-torque IBS demonstration discharges suggests their onset time occurs randomly in the constant β phase, most often triggered by non-linear 3-wave coupling, thus identifying an NTM seeding mechanism to avoid. Pure deuterium SPI for disruption mitigation is shown to provide favorable slow cooling, but poor core assimilation, suggesting paths for improved SPI on ITER. At the boundary, measured neutral density and ionization source fluxes are strongly poloidally asymmetric, implying a 2D treatment is needed to model pedestal fuelling. Detailed measurements of pedestal and SOL quantities and impurity charge state radiation in detached divertors has validated edge fluid modelling and new self-consistent ‘pedestal-to-divertor’ integrated modeling that can be used to optimize reactors. New feedback adaptive ELM control minimizes confinement reduction, and RMP ELM suppression with sustained high core performance was obtained for the first time with the outer strike point in a W-coated, compact and unpumped small-angle slot divertor. Advances have been made in integrated operational scenarios for ITER and power plants. Wide pedestal intrinsically ELM-free QH-modes are produced with more reactor-relevant conditions, Low torque IBS with W-equivalent radiators can exhibit predator-prey oscillations in T _e and radiation which need control. High- β _P scenarios with q _min > 2, q _95 –7.9, β _N > 4, β _T –3.3% and H _98y2 > 1.5 are sustained with high density ( $\bar n$ = 7E19 m ^−3 , f _G –1) for 6 τ _E , improving confidence in steady-state tokamak reactors. Diverted NT plasmas achieve high core performance with a non-ELMing edge, offering a possible highly attractive core-edge integration solution for reactors.

Published
2024
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5. Analysis and design of fast flow liquid Li divertor for fusion nuclear science facility (FNSF) using coupled plasma boundary and LM MHD/heat transfer codes

Author

M.S. Islam, J.D. Lore, S. Smolentsev, C.E. Kessel, and R. Maingi

Subjects
SOLPS-ITER, FNSF, liquid metal (LM) divertor, MHD heat transfer, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

The SOLPS-ITER code is utilized to analyze the boundary plasma associated with a fast-flow lithium (Li) divertor configuration in the fusion nuclear science facility (FNSF) tokamak and identify operational regimes with acceptable divertor and core conditions. Plasma transport from the SOLPS-ITER code has been coupled with a liquid metal (LM) MHD/heat transfer code to model a Li open-surface divertor design and assess its impact on the scrape-off-layer (SOL) and core plasma performance. Simulations with only Neon (Ne) impurity seeding have been conducted to evaluate its impact on meeting FNSF design demands for the divertor and upstream plasma parameters. Simulation results indicate that Ne seeding significantly mitigates divertor heat flux but potentially reduces both upstream electron and main ion density due to fuel dilution. The combined application of Ne seeding and deuterium (D _2 ) puffing is required to satisfy the FNSF design requirements on upstream density ( $n_{e,\textrm{sep}}^\textrm{OMP}$ ∼1× 10 ^20 m ^−3 ) and divertor energy flux ( $q_{\perp,\textrm{max}}^\textrm{Odiv}$ $\lt $ 10 MW m ^−2 ). D _2 puffing plays a role in counteracting upstream density drops and augmenting energy and momentum losses through atomic and molecular processes. The inlet Li flow velocity is systematically varied across a wide range to identify acceptable flows and corresponding LM surface temperatures. This comprehensive analysis identifies the acceptable Li flow parameters, LM surface temperature, and emitted Li fluxes necessary to meet the major design constraints. The emitted Li fluxes exhibit minimal impact on the main plasma at surface temperatures up to approximately ∼525 ^∘ C, corresponding emitted Li fluxes of up to φ _Li ∼2 $\times 10^{23}$ atoms s ^−1 . Uncertainties in the Li emission processes from the surface are also investigated, primarily influencing Li loss in the lower surface temperature range ( ${\lt}525\,^{\circ}$ C), with simulation results indicating a minor impact on the divertor and upstream plasma. Conversely, evaporation predominantly drives the Li loss processes at higher surface temperature ranges ( ${\gt}525\,^{\circ}$ C), contaminating both the divertor and upstream plasma.

Published
2024
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6. NSTX-U research advancing the physics of spherical tokamaks

Author

J.W. Berkery, P.O. Adebayo-Ige, H. Al Khawaldeh, G. Avdeeva, S-G. Baek, S. Banerjee, K. Barada, D.J. Battaglia, R.E. Bell, E. Belli, E.V. Belova, N. Bertelli, N. Bisai, P.T. Bonoli, M.D. Boyer, J. Butt, J. Candy, C.S. Chang, C.F. Clauser, L.D. Corona Rivera, M. Curie, P.C. de Vries, R. Diab, A. Diallo, J. Dominski, V.N. Duarte, E.D. Emdee, N.M. Ferraro, R. Fitzpatrick, E.L. Foley, E. Fredrickson, M.E. Galante, K.F. Gan, S. Gerhardt, R. Goldston, W. Guttenfelder, R. Hager, M.O. Hanson, S.C. Jardin, T.G. Jenkins, S.M. Kaye, A. Khodak, J. Kinsey, A. Kleiner, E. Kolemen, S. Ku, M. Lampert, B. Leard, B.P. LeBlanc, J.B. Lestz, F.M. Levinton, C. Liu, T. Looby, R. Lunsford, T. Macwan, R. Maingi, J. McClenaghan, J.E. Menard, S. Munaretto, M. Ono, A. Pajares, J. Parisi, J-K. Park, M.S. Parsons, B.S. Patel, Y.V. Petrov, M. Podestà, F. Poli, M. Porcelli, T. Rafiq, S.A. Sabbagh, Á. Sánchez Villar, E. Schuster, J. Schwartz, A. Sharma, S. Shiraiwa, P. Sinha, D. Smith, S. Smith, V.A. Soukhanovskii, G. Staebler, E. Startsev, B. Stratton, K.E. Thome, W. Tierens, M. Tobin, I.U. Uzun-Kaymak, B. Van Compernolle, J. Wai, W. Wang, W. Wehner, A. Welander, J. Yang, V. Zamkovska, X. Zhang, X.L. Zhu, and S. Zweben

Subjects
spherical tokamak, magnetic confinement fusion, NSTX, NSTX-U, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

The objectives of NSTX-U research are to reinforce the advantages of STs while addressing the challenges. To extend confinement physics of low- A , high beta plasmas to lower collisionality levels, understanding of the transport mechanisms that set confinement performance and pedestal profiles is being advanced through gyrokinetic simulations, reduced model development, and comparison to NSTX experiment, as well as improved simulation of RF heating. To develop stable non-inductive scenarios needed for steady-state operation, various performance-limiting modes of instability were studied, including MHD, tearing modes, and energetic particle instabilities. Predictive tools were developed, covering disruptions, runaway electrons, equilibrium reconstruction, and control tools. To develop power and particle handling techniques to optimize plasma exhaust in high performance scenarios, innovative lithium-based solutions are being developed to handle the very high heat flux levels that the increased heating power and compact geometry of NSTX-U will produce, and will be seen in future STs. Predictive capabilities accounting for plasma phenomena, like edge harmonic oscillations, ELMs, and blobs, are being tested and improved. In these ways, NSTX-U researchers are advancing the physics understanding of ST plasmas to maximize the benefit that will be gained from further NSTX-U experiments and to increase confidence in projections to future devices.

Published
2024
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7. Optimization of lithium vapor box divertor evaporator location on NSTX-U using SOLPS-ITER

Author

E.D. Emdee, R.J. Goldston, A. Khodak, and R. Maingi

Subjects
lithium vapor box, detachment, CPSF, SOLPS, divertor, NSTX-U, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Commercial fusion reactors will be faced with extremely high divertor target heat fluxes that will require mitigation. Simulations of detachment in an NSTX-U scenario projected to have 92 MW m ^−2 unmitigated peak target heat flux are presented, which reaches sub-10 MW m ^−2 target heat flux using a highly dissipating lithium vapor box divertor design. The lithium vapor box is a detached divertor design which employs lithium vapor evaporation and condensation to contain lithium below the X-point. Previous SOLPS modeling has indicated a lithium vapor box can reduce the heat flux down to 10 MW m ^−2 via simultaneous evaporation from the Private Flux Region (PFR) and the Common Flux Region (CFR) sides of the vapor box. It is found here that PFR evaporation has improved access to the separatrix leading to significantly more efficient power dissipation than CFR evaporation. Simulations of target evaporation with an evaporation distribution that is self-consistent with the temperature of a Capillary Porous System with Fast flowing liquid lithium could reach $n_\textrm{Li}$ / $n_\textrm{e} \sim$ 0.025–0.030 at the Last Closed Flux Surface (LCFS) depending on the liquid metal flow speeds and lithium sputtering yield, while PFR-side evaporation can reach acceptable heat fluxes with $n_\textrm{Li}$ / $n_\textrm{e} \sim$ 0.038 at the LCFS. However, PFR evaporator performance can be improved if the target is allowed to be hot enough such that it reflects lithium, reaching $n_\textrm{Li}$ / $n_\textrm{e} \sim$ 0.028 and reducing required lithium evaporation. Ultimately PFR evaporation and target evaporation are found to have similar ability to produce acceptable heat flux solutions with minimal upstream concentration.

Published
2024
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8. Overview of recent results from the ST40 compact high-field spherical tokamak

Author

S.A.M. McNamara, A. Alieva, M.S. Anastopoulos Tzanis, O. Asunta, J. Bland, H. Bohlin, P.F. Buxton, C. Colgan, A. Dnestrovskii, E. du Toit, M. Fontana, M. Gemmell, M.P. Gryaznevich, J. Hakosalo, M.R. Hardman, D. Harryman, D. Hoffman, M. Iliasova, S. Janhunen, F. Janky, J.B. Lister, H.F. Lowe, E. Maartensson, C. Marsden, S.Y. Medvedev, S.R. Mirfayzi, M. Moscheni, G. Naylor, V. Nemytov, J. Njau, T. O’Gorman, D. Osin, T. Pyragius, A. Rengle, M. Romanelli, C. Romero, M. Sertoli, V. Shevchenko, J. Sinha, A. Sladkomedova, S. Sridhar, J. Stirling, Y. Takase, P.R. Thomas, J. Varje, E. Vekshina, B. Vincent, H.V. Willett, J. Wood, E. Wooldridge, D. Zakhar, X. Zhang, D. Battaglia, N. Bertelli, P.J. Bonofiglo, L.F. Delgado-Aparicio, V.N. Duarte, N.N. Gorelenkov, M. de Haas, S.M. Kaye, R. Maingi, D. Mueller, M. Ono, M. Podesta, Y. Ren, S. Trieu, E. Delabie, T.K. Gray, B. Lomanowski, E.A. Unterberg, O. Marchuk, and the ST40 Team

Subjects
spherical tokamak, high-field, ST40, overview, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

ST40 is a compact, high-field ( $B_{\mathrm{T0}}\unicode{x2A7D} 2.1\,\,\,\textrm{T}$ ) spherical tokamak (ST) with a mission to expand the physics and technology basis for the ST route to commercial fusion. The ST40 research programme covers confinement and stability; solenoid-free start-up; high-performance operating scenarios; and plasma exhaust. In 2022, ST40 obtained central deuterium ion temperatures of $9.6 \pm 0.4\ \textrm{keV}$ , demonstrating for the first time that pilot plant relevant ion temperatures can be reached in a compact, high-field ST. Analysis of these high-ion temperature plasmas is presented, including a summary of confinement, transport and microstability characteristics, and energetic particle instabilities. Recent scenario development activities have focused on establishing diverted H-mode plasmas across a range of toroidal fields and plasma currents, along with scenarios with high non-inductive current fractions. In future operations, beginning in 2025, a 1 MW dual frequency (104/137 GHz) electron cyclotron (EC) system will be installed to enable the study of EC and electron Bernstein wave plasma start-up and current drive. Predictive modelling of the potential performance of these systems is presented.

Published
2024
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9. The formation of an radial edge electric field due to finite ion orbit width effects is the possible root cause of the H-mode edge

Author

G.J. Kramer, A. Bortolon, A. Diallo, and R. Maingi

Subjects
H-mode plasma edge, full orbit simulations, edge electric field, tokamaks, E × B velocity shear, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Full orbit-following simulations of thermal ions show that finite ion-orbit width effects create charge separation near the last closed flux surface (LCFS) which generates a localized radial electric field. Experimentally, edge electric fields are observed in H-mode plasmas and they are necessary for the edge turbulence suppression via the $\boldsymbol{ E \times B }$ flow shear mechanism. Confined trapped (and to a lesser extent co-passing) ions near the plasma edge form a positive charge distribution outside the LCFS, while thermal electrons are tied more tightly to field lines owing to their small mass and are poorly confined outside the LCFS, hence charge neutrality is violated outside the LCFS. A large number of reported observations from spherical and conventional tokamaks support the results from the simulations although the simulations were not performed fully self consistently. The results suggest ways to lower the H-mode power threshold and optimize the H-mode plasma edge.

Published
2024
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10. Divertor heat load estimates on NSTX and DIII-D using new and open-source 2D inversion analysis code

Author

P.O. Adebayo-Ige, K.F. Gan, C.J. Lasnier, R. Maingi, and B.D. Wirth

Subjects
infrared thermography, heat flux, divertor, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

A thermography inversion algorithm has been developed in the open-source Python-based computer code, HYPERION, to calculate the heat flux incident on plasma-facing components (PFCs) in axisymmetric tokamaks. The chosen mesh size at the surface significantly affects the calculated transient heat flux results. The calculated transient heat flux will exceed the real value when the mesh size tends to zero but will underestimate the real value when the mesh size is large. A criterion for determining the appropriate mesh size for the transient heat flux calculation will be discussed. The numerical scheme for HYPERION uses a 2D fully implicit finite-difference approach, allowing temperature-dependent thermal properties of PFC materials. The inversion algorithm is benchmarked against established heat flux calculation codes, TACO and THEODOR, based on thermography data from NSTX and DIII-D respectively. The primary benefits of HYPERION compared to TACO and THEODOR are that it is open-source and it allows for the optimization of mesh thickness along the substrate. The algorithm also accounts for the thermal properties of thin surface layers that characteristically form on PFCs due to plasma-material interactions. The agreement between HYPERION and THEODOR is excellent, as the percent difference between the codes is ∼5% on average in the case of the DIII-D data for moderate to high heat flux. Verification tests with TACO show slightly higher average percent differences of 8% and 12%. In using HYPERION to study filaments in heat flux, the initial results indicate that small ELMs filaments significantly broaden the divertor heat flux, and decrease divertor peak flux. Compared to the inter-ELM, the small ELM filaments decrease the divertor peak surface temperature. With intermittent divertor filaments, the divertor heat flux width is comparable with that found in L-mode.

Published
2024
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11. Active wall conditioning through boron powder injection compatible ELM control in EAST

Author

W. Xu, Z. Sun, R. Maingi, G.Z. Zuo, Y.W. Yu, C.L. Li, Y.H. Guan, Z.T. Zhou, X.C. Meng, M. Huang, L. Zhang, W. Gao, and J.S. Hu

Subjects
Boron powder, Wall conditioning, ELM control, EAST, Nuclear engineering. Atomic power, TK9001-9401
Abstract

Real-time wall conditioning and edge-localized mode (ELM) suppression through real-time boron powder injection into high-confinement mode discharges of the Experimental Advanced Superconducting Tokamak (EAST) have been investigated. The boron powder injection effectively conditioned the plasma-facing components, as shown by the reductions in low-Z and high-Z impurities and the global recycling level in the whole inner vessel, and suppressed the strong magnetohydrodynamic (MHD) activity in the plasma core. The improved wall conditions also resulted in an earlier transition from L- to H-mode. Boron powder injection also effectively suppressed ELM in the lower single null configuration with BT in the favorable direction while leaving the plasma density and stored energy largely unaffected.

Published
2023
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12. Effect of continuously flowing liquid Li limiter on particle and heat fluxes during H-mode discharges in EAST

Author

G.Z. Zuo, C.L. Li, R. Maingi, X.C. Meng, D. Andruczyk, P.J. Sun, Z. Sun, W. Xu, M. Huang, Z.L. Tang, D.H. Zhang, Y.J. Chen, Q. Zang, Y.M. Wang, Y.F. Wang, K. Tritz, and J.S. Hu

Subjects
Liquid Li, Particle flux, Heat flux, H-mode, EAST, Nuclear engineering. Atomic power, TK9001-9401
Abstract

Particle and heat fluxes were successfully controlled by using a continuously flowing liquid Li (FLiLi) limiter in the H-mode discharges with high plasma heating power in the Experimental Advanced Superconducting Tokamak device. There were strong interactions between the FLiLi limiter and high-power plasma with a ∼ 8.3 MW source heating power, and successively, a bright Li radiation ring was produced, which effectively decreased fuel particle recycling by approximately 50%. Due to Li efflux from FLiLi during a series of high-power discharges, an obvious real-time wall conditioning effect was produced, and fuel particle recycling further decreased. Moreover, the value of Zeff decreased from 2.3 to 1.6 due to a decrease in impurity sources; this was attributed to the accumulation of Li deposited on the first wall, which effectively protected the wall materials. The decreased recycling and impurity radiation achieved high-energy confinement plasma, and the average stored energy increased up to ∼ 290 kJ. Moreover, due to the effect of Li vapor shielding, nearly 30% plasma heat flux was dissipated before it arrived at the Li limiter. These results promote further exploration of liquid Li solutions for the critical challenge of heat flux handling and particle control in fusion power plants.

Published
2022
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13. Conference Report on the 7th International Symposium on Liquid metals Applications for fusion (ISLA-7)

Author

Y. Hirooka, A. de Castro, T. Goto, R. Maingi, T.W. Morgan, M. Ono, and M. Shimada

Subjects
liquid metal applications, nuclear fusion reactor, plasma-surface interactions, divertor, plasma-facing components, liquid metal plasma-facing components, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Supported by the world magnetic fusion research community, a series of International Symposia on Liquid metals Applications for fusion (ISLA) have been held biannually since 2010. The 7th edition (ISLA-7) was held for the period from 12 December through 16 December 2022, at Chubu University located in Kasugai, Aichi, Japan. For the first time in the history of this series of symposia, ISLA-7 was held in a hybrid fashion, due to the COVID-19 situation. The total number of the participants was 60, 34 out of whom attended the symposium in person, and the rest participated online. As to the presentation statistics, 29 papers were presented in person, whereas 21 presentations were delivered online but real-time by the presenters in China, Spain, the UK, and the USA. Both of the presentations delivered in person and online were recorded, and the video has been shared by all participants. These participants represent 11 countries: China, Czech, Italy, Japan, Latvia, Netherlands, Russia, Thailand, the UK, and the USA. All these numbers are among the largest in this series of symposia. Covered by these presentations are; in session-2, program overviews and liquid metal research review; in session-3, liquid metal flows, and MHD issues; in session-4, liquid metal facilities; in sessions-5 and 6, liquid metal experiments and modeling; in session-7, divertor physics and heat flux mitigation; in session-8, plasma and liquid metals interactions; in session-9 liquid metal plasma-facing components, erosion, and wettability. In addition, there were an opening session whereby several opening addresses were delivered and also a closing session where all technical session summaries were presented by the respective session chairs.

Published
2023
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14. Achievement of ion temperatures in excess of 100 million degrees Kelvin in the compact high-field spherical tokamak ST40

Author

S.A.M. McNamara, O. Asunta, J. Bland, P.F. Buxton, C. Colgan, A. Dnestrovskii, M. Gemmell, M. Gryaznevich, D. Hoffman, F. Janky, J.B. Lister, H.F. Lowe, R.S. Mirfayzi, G. Naylor, V. Nemytov, J. Njau, T. Pyragius, A. Rengle, M. Romanelli, C. Romero, M. Sertoli, V. Shevchenko, J. Sinha, A. Sladkomedova, S. Sridhar, Y. Takase, P. Thomas, J. Varje, B. Vincent, H.V. Willett, J. Wood, D. Zakhar, D.J. Battaglia, S.M. Kaye, L.F. Delgado-Aparicio, R. Maingi, D. Mueller, M. Podesta, E. Delabie, B. Lomanowski, O. Marchuk, and the ST40 Team

Subjects
ST40, high-field, spherical tokamak, compact, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Ion temperatures of over 100 million degrees Kelvin (8.6 keV) have been produced in the ST40 compact high-field spherical tokamak (ST). Ion temperatures in excess of 5 keV have not previously been reached in any ST and have only been obtained in much larger devices with substantially more plasma heating power. The corresponding fusion triple product is calculated to be ${n_{i0}}{T_{i0}}{\tau _E} \approx 6 \pm 2 \times {10^{18}}{{\text{m}}^{ - 3}}{\text{keVs}}$ . These results demonstrate for the first time that ion temperatures relevant for commercial magnetic confinement fusion can be obtained in a compact high-field ST and bode well for fusion power plants based on the high-field ST.

Published
2023
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15. Magnetohydrodynamics in free surface liquid metal flow relevant to plasma-facing components

Author

Z. Sun, J. Al Salami, A. Khodak, F. Saenz, B. Wynne, R. Maingi, K. Hanada, C.H. Hu, and E. Kolemen

Subjects
plasma-facing components, free surface, MHD, liquid metal, CFD, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

While flowing Liquid Metal (LM) Plasma-Facing Components (PFCs) represent a potentially transformative technology to enable long-pulse operation with high-power exhaust for fusion reactors, Magnetohydrodynamic (MHD) drag in the conducting LM will reduce the flow speed. Experiments have been completed in the linear open-channel LMX-U device [Hvasta et al 2018 Nucl. Fusion 58 01602] for validation of MHD drag calculations with either insulating or conducting walls, with codes similar to those used to design flowing LM PFCs for a Fusion Nuclear Science Facility [Kessel et al 2019 Fusion Sci. Technol . 75 886]. We observe that the average channel flow speed decreased with the use of conducting walls and the strength of the applied transverse magnetic field. The MHD drag from the retarding Lorentz force resulted in an increase of the LM depth in the channel that ‘piled up’ near the inlet, but not the outlet. As reproduced by OpenFOAM and ANSYS CFX calculations, the magnitude and characteristics of the pileup in the flow direction increased with the applied traverse magnetic field by up to 120%, as compared to the case without an applied magnetic field, corresponding to an average velocity reduction of ∼45%. Particle tracking measurements confirmed a predicted shear in the flow speed, with the surface velocity increasing by 300%, despite the 45% drop in the average bulk speed. The MHD effect makes the bulk flow laminarized but keeps surface waves aligned along the magnetic field lines due to the anisotropy of MHD drag. The 3D fringe field and high surface velocity generate ripples around the outlet region. It was also confirmed that the MHD drag strongly depends on the conductivity of the channel walls, magnetic field, and volumetric flow rate, in agreement with the simulations and a developed analytical model. These validated models are now available to begin to determine the conditions under which the ideal LM channel design of a constant flow speed and fluid depth could be attained.

Published
2023
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16. Extending the low-recycling, flat temperature profile regime in the lithium tokamak experiment-β (LTX-β) with ohmic and neutral beam heating

Author

D.P. Boyle, J. Anderson, S. Banerjee, R.E. Bell, W. Capecchi, D.B. Elliott, C. Hansen, S. Kubota, B.P. LeBlanc, A. Maan, R. Maingi, R. Majeski, J.E. Menard, S. Oliva, T. Rhodes, V. Soukhanovskii, and L. Zakharov

Subjects
low-recycling, lithium, tokamak, plasma–surface interactions, ohmic confinement, neutral beam injection, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Recent experiments in the lithium tokamak experiment- β (LTX- β ) have extended the duration, performance, operating conditions, and diagnosis of the flat-temperature profile, low-recycling regime first observed in LTX. As expected, Li retains hydrogen and suppresses edge neutral cooling, allowing increased edge electron temperature, roughly equal to the core T _e . Flat temperature profiles had been obtained transiently in LTX, as the plasma density decayed following the cessation of edge gas puffing. Careful control over the fueling in LTX- β has now been shown to sustain the flat T _e profile and hot edge unique to the low-recycling regime for multiple confinement times in high performance discharges with decaying or steady density. With low density, the flat T _e profile is also seen to extend into the scrape-off layer. Neutral beam heating is observed in target discharges with relatively flat electron temperature profiles ( T _edge ∼ T _core /2), though beam heating is stronger in discharges with higher fueling, higher density, and depressed edge T _e . Beam heating produces additional peaking of the T _e profile, without degradation of the energy confinement time. Neutral beam heating of target discharges with relatively flat electron temperature profiles similarly results in broad beam heated temperature profiles. Energy confinement in LTX- β generally compares favorably to ohmic and H-mode scalings, frequently exceeding them by factors of 2–4. New and improved diagnostics in LTX- β enable better characterization of this unique regime, including measurements of ion temperature and high field side Thomson scattering profiles. As an initial step toward characterizing turbulence with no T _e gradient and roughly equal density and pressure gradient, core fluctuation spectra have been measured in peaked T _e discharges using far-forward scattering and fluctuation reflectometry.

Published
2023
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17. Wall conditioning and ELM mitigation with boron nitride powder injection in KSTAR

Author

E.P. Gilson, H.H. Lee, A. Bortolon, W. Choe, A. Diallo, S.H. Hong, H.M. Lee, J. Lee, R. Maingi, D.K. Mansfield, A. Nagy, S.H. Park, I.W. Song, J.I. Song, S.W. Yun, S.W. Yoon, and R. Nazikian

Subjects
Wall conditioning, Edge-localized mode, ELM, Impurity, Boron nitride, Nuclear engineering. Atomic power, TK9001-9401
Abstract

Results from KSTAR powder injection experiments, in which tens of milligrams of boron nitride (BN) were dropped into low-power H-mode plasmas, show an improvement in wall conditions in subsequent discharges and, in some cases, a reduction or elimination of edge-localized modes (ELMs). Injected powder is distributed by the plasma flow and is deposited on the wall and, over the course of several discharges, was observed to gradually reduce recycling by 33%, and decrease both the ELM amplitude and frequency. This is the first demonstration of the use of BN for ELM mitigation. In all of these experiments, an Impurity Powder Dropper (IPD) was used to introduce precise, controllable amounts of the materials into ELMy H-mode KSTAR discharges. The plasma duration was between 10 s and 15 s, Ip=500 kA, BT=1.8 T, PNBI=1.6 MW, and PECH=0.6 MW. Plasma densities were between 2 and 3×1019 m−3. In all cases, the pre-fill and startup gas-fueling was kept constant, suggesting that the decrease in baseline Dαemission is in fact due to a reduction in recycling. The results presented herein highlight the viability of powder injection for intra-shot and between-shot wall conditioning.

Published
2021
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18. Real time wall conditioning with lithium powder injection in long pulse H-mode plasmas in EAST with tungsten divertor

Author

Z. Sun, R. Maingi, J.S. Hu, W. Xu, G.Z. Zuo, Y.W. Yu, C.R. Wu, M. Huang, X.C. Meng, L. Zhang, L. Wang, S.T. Mao, F. Ding, D.K. Mansfield, J. Canik, R. Lunsford, A. Bortolon, and X.Z. Gong

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

Real-time lithium powder injection has been applied to long-pulse (>30 s) H-mode plasmas in EAST. This replenishes the active lithium surface that is routinely consumed by plasma-wall interactions. The real-time injection of Li powder into long H-mode discharges effectively suppresses impurity influx and controls recycling on EAST, with an ITER-like tungsten upper divertor. With lithium powder injection, the concentrations W, Mo, and C were reduced by 50% compared to ELMy H-mode discharges. During lithium injection, two effects play a role in the suppression of impurities influx: a reduced divertor temperature and heat flux and hence reduced erosion, and impurity trapping via deposition of a Li film onto plasma-facing surfaces. The ‘fresh’ injected lithium replenishes the film deposited during daily morning evaporation, restoring the wall's pumping capability. Thus, a measurable reduction in the global recycling coefficient was observed. Keyword: Long pulse plasma, Lithium, Impurity, Recycling

Published
2019
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19. Real-time wall conditioning by controlled injection of boron and boron nitride powder in full tungsten wall ASDEX Upgrade

Author

A. Bortolon, V. Rohde, R. Maingi, E. Wolfrum, R. Dux, A. Herrmann, R. Lunsford, R.M. McDermott, A. Nagy, A. Kallenbach, D.K. Mansfield, R. Nazikian, and R. Neu

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

In ASDEX Upgrade with full-tungsten wall, boronization is an important tool to control tungsten sources and allow reliable operation at low collisionality. The duration of the beneficial effects is limited by the erosion of the boron layer, in particular on the tungsten ion-cyclotron antenna limiters. We report results from experiments exploring injection boron-rich powders in tokamak plasmas as a way to replenish boron coating and extend the lifetime of boronization effects. Pure boron and boron nitride powders were introduced gravitationally in plasma discharges at rates up to 60 mg/s for durations up to 3 s. Boron injection with cumulative amounts >100 mg appeared to improve wall conditions similarly to boronization, with indications of reduced influx of oxygen and tungsten from the antenna limiter. Moreover, cumulative injection of 340 mg of B appeared sufficient to enable successful execution of low collisionality scenarios critically relying on freshly boronized walls.

Published
2019
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20. Supplemental ELM control in ITER through beryllium granule injection

Author

R. Lunsford, A. Bortolon, R. Maingi, D.K. Mansfield, A. Nagy, G.L. Jackson, and T. Osborne

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

Injection of low-Z granules into high performance discharges on DIII-D has been shown to promptly trigger Edge Localized Modes (ELMs) providing high-Z impurity control without significant plasma degradation. The ability to provide ELM triggering over a range of injection and discharge parameters suggests that the mechanical introduction of granules can be considered as an additional method of impurity control in ITER. Utilizing a spherically symmetric vapor shielding model for granule ablation, benchmarked with impurity granule injections on DIII-D, we simulate the injection of beryllium granules into ITER baseline discharges. By comparing the granule induced ELM triggering size required for deuterium and non-fuel pellets on DIII-D and cross-correlating with a previously simulated JOREK calcuation of D pellet size required for ELM triggering in ITER, we estimate that a beryllium pellet of 1.5 mm diameter should provide reliable ELM triggering on ITER. This size pellet, delivered at 200 m/s should penetrate 3.5 cm past the separatrix, solidly within the H-mode steep gradient region, a location found to be advantageous for ELM triggering with minimal pellet size. Keywords: ELM pacing, granule injection, beryllium

Published
2019
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21. Design of the Flowing LIquid Torus (FLIT)

Author

E. Kolemen, M. Hvasta, R. Majeski, R. Maingi, A. Brooks, and T. Kozub

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

The design of the Flowing LIquid Torus (FLIT) at Princeton Plasma Physics Laboratory (PPPL) is presented. FLIT will focus on the development of a liquid metal (LM) diagnostics and divertor system (without a plasma source) suitable for implementation in present-day fusion systems, such as NSTX-U. FLIT is intended to provide proof-of-concept for fast-flowing LM divertor designs for heat fluxes > 10 MW/m2. The toroidal test article (ID ≈ 0.56 m, OD ≈ 1.9 m, h ≈ 0.61 m) consists of 12 rectangular coils that can generate a centerline magnetic field of 1 T magnetic for greater than 10 s. Initially, 30 gallons Galinstan (Ga-In-Sn eutectic) will be recirculated within the test article using six jxB pumps to achieve flow velocities of up to 10 m/s across the fully annular radial test section. FLIT is designed to be a flexible machine that will allow experimental testing of various LM injection techniques, the study of flow instabilities, and electromagnetic control concepts to prove the feasibility of the LM divertors within fusion reactors.

Published
2019
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22. Experiments of continuously and stably flowing lithium limiter in EAST towards a solution for the power exhaust of future fusion devices

Author

J.S. Hu, G.Z. Zuo, R. Maingi, Z. Sun, K. Tritz, W. Xu, Q.X. Yang, D. Andruczyk, M. Huang, X.C. Meng, X.Z. Gong, D.N. Ruzic, M.J. Ni, B.N. Wan, and J.G. Li

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

Liquid lithium (Li) can partly ameliorate lifetime and power-exhaust issues of plasma facing components (PFCs) by enabling a self-healing, self-replenishing surface with a reduced susceptibility to neutron damage in future fusion devices. To assess operational stability and heat-exhaust capability under tokamak exposure, two generations of continuously flowing liquid Li (FLiLi) limiters on the concept of a thin flowing Li film have been successfully designed and tested in high performance discharges in EAST. The design uses a circulating Li layer with a thickness of

Published
2019
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23. 3D modeling of boron transport in DIII-D L-mode wall conditioning experiments

Author

F. Effenberg, A. Bortolon, H. Frerichs, B. Grierson, J.D. Lore, T. Abrams, T.E. Evans, Y. Feng, R. Lunsford, R. Maingi, A. Nagy, R. Nazikian, D. Orlov, J. Ren, D.L. Rudakov, W.R. Wampler, and H.Q. Wang

Subjects
Wall conditioning, Boronization, Impurity seeding, Impurity flows, EMC3-EIRENE, Nuclear engineering. Atomic power, TK9001-9401
Abstract

DIII-D L-mode experiments with local boron powder injection for real-time wall conditioning have been interpreted for the first time with the 3D plasma edge transport Monte Carlo code EMC3-EIRENE. Local B sourcing in plasma scenarios with upstream densities 1.5⋅1019m−3 and 2.2 MW heating results in a non-axisymmetric B distribution in the scrape-off layer (SOL) and on the divertor. The SOL frictional flows at high plasma density cause a strong inboard drag of injected impurities (≈90%), while lower background plasma densities tend to result in a more uniform distribution. The thermal forces prevent B deposition in the near SOL while the frictional force causes B fluxes to cover the divertor plasma-facing components in a region 7–10 cm beyond the strike line. Radiative dissipation occurs for B influxes above 1⋅1020s−1 and causes a moderate, non-axisymmetric reduction of the far SOL divertor heat fluxes. A comparison of top and midplane B injection shows no substantial difference in inboard vs. outboard asymmetries of the B distribution. On the other hand, erosion or recycling at the strike line may distribute the boron more uniformly in the SOL.

Published
2021
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24. Lithium splashing from flowing liquid lithium limiter and its effect on high confinement plasma performance in EAST tokamak

Author

Z.L. Tang, G.Z. Zuo, C.L. Li, R. Maingi, X.C. Meng, W. Xu, Z. Sun, Y.Z. Qian, M. Huang, D.H. Zhang, D. Andruczyk, K. Tritz, X.L. Yuan, X.B. Zhang, and J.S. Hu

Subjects
Flowing liquid Li limiter, Splashing, Rayleigh-Taylor instability, EAST, Nuclear engineering. Atomic power, TK9001-9401
Abstract

To study the potential applications of liquid lithium (Li) as plasma facing material, the third generation of flowing liquid Li (FLiLi) limiter has been designed and successfully tested in EAST tokamak H-mode discharges in the 2018 run campaign. The stability of liquid Li on FLiLi surface, and Li splashing and its effect on the plasma performance are investigated in detail. Li splashing was observed in L-mode and H-mode discharges due to Rayleigh-Taylor (R-T) instability, resulting from electromagnetic forces J→×B→. Li splashing in low-parameter plasma decreased both core and edge electron temperatures, resulting in the degradation of plasma energy confinement and even H-L back transition, however, it almost did not influence plasma confinement performance in high-parameter plasma. These findings indicate that high-parameter plasma has higher tolerance to Li impurities than low-parameter plasma. By contrast, tungsten splashing from the melted layer on the upper divertor was also induced by the R-T instability but generally resulted in plasma disruption, which suggests lower tolerance to tungsten impurities in EAST tokamak.

Published
2020
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25. Modeling of lithium granule injection in NSTX with M3D-C1

Author

A. Fil, E. Kolemen, A. Bortolon, N. Ferraro, S. Jardin, P.B. Parks, R. Lunsford, and R. Maingi

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

In this paper we present initial simulations of pedestal control by Lithium Granule Injection (LGI) in NSTX. A model for small granule ablation has been implemented in the M3D-C1 code [1], allowing the simulation of realistic Lithium granule injections. 2D simulations in NSTX L-mode and H-mode plasmas are done and the effect of granule size, injection angle and velocity on the pedestal gradient increase are studied. For H-mode cases, the amplitude of the local pressure perturbation caused by the granules is highly dependent on the solid granule size. In our simulations, reducing the granule injection velocity allows one to inject more particles at the pedestal top.

Published
2017
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26. Effect of heating scheme on SOL width in DIII-D and EAST

Author

L. Wang, M.A. Makowski, H.Y. Guo, A.W. Leonard, G.S. Xu, X.Z. Gong, A.M. Garofalo, G.Z. Deng, T.W. Petrie, D. Thomas, G. Jackson, G. Kramer, R. Maingi, J.B. Liu, W. Feng, H. Wang, B. Zhang, S. Ding, C.K. Pan, Y.J. Hu, J.P. Qian, J. Li, and B.N. Wan

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

Joint DIII-D/EAST experiments in the radio-frequency (RF) heated H-mode scheme with comparison to that of neutral beam (NB) heated H-mode scheme were carried out on DIII-D and EAST under similar conditions to examine the effect of heating scheme on scrape-off layer (SOL) width in H-mode plasmas for application to ITER. A dimensionally similar plasma equilibrium was used to match the EAST shape parameters. The divertor heat flux and SOL widths were measured with infra-red camera in DIII-D, while with divertor Langmuir probe array in EAST. It has been demonstrated on both DIII-D and EAST that RF-heated plasma has a broader SOL than NB-heated plasma when the edge electrons are effectively heated in low plasma current and low density regime with low edge collisionality. Detailed edge and pedestal profile analysis on DIII-D suggests that the low edge collisionality and ion orbit loss effect may account for the observed broadening. The joint experiment in DIII-D has also demonstrated the strong inverse dependence of SOL width on the plasma current in electron cyclotron heated (ECH) H-mode plasmas. Keywords: SOL width, Radio-frequency heating, Neutral beam heating, Low collisionality

Published
2017
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27. Elimination of inter-discharge helium glow discharge cleaning with lithium evaporation in NSTX

Author

R. Maingi, R. Kaita, F. Scotti, and V.A. Soukhanovskii

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

Operation in the National Spherical Torus Experiment (NSTX) typically used either periodic boronization and inter-shot helium glow discharge cleaning (HeGDC), or inter-shot lithium evaporation without boronization, and initially with inter-shot HeGDC. To assess the viability of operation without HeGDC, dedicated experiments were conducted in which Li evaporation was used while systematically shrinking the HeGDC between shots from the standard 10min to zero (10→6.5→4→0). Good shot reproducibility without HeGDC was achieved with lithium evaporations of 100mg or higher; evaporations of 200–300mg typically resulted in very low ELM frequency or ELM-free operation, reduced wall fueling, and improved energy confinement. The use of HeGDC before lithium evaporation modestly reduced Dα in the outer scrape-off layer, but not at the strike point. Pedestal electron and ion temperature also improved modestly, suggesting that HeGDC prior to lithium evaporation is a useful tool for experiments that seek to maximize plasma performance. Keywords: NSTX, Lithium, Recycling, Pedestal, Energy confinement

Published
2017
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28. Kinetic simulations of scrape-off layer physics in the DIII-D tokamak

Author

R.M. Churchill, J.M. Canik, C.S. Chang, R. Hager, A.W. Leonard, R. Maingi, R. Nazikian, and D.P. Stotler

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

Simulations using the fully kinetic code XGCa were undertaken to explore the impact of kinetic effects on scrape-off layer (SOL) physics in DIII-D H-mode plasmas. XGCa is a total-f, gyrokinetic code which self-consistently calculates the axisymmetric electrostatic potential and plasma dynamics, and includes modules for Monte Carlo neutral transport. Fluid simulations are normally used to simulate the SOL, due to its high collisionality. However, depending on plasma conditions, a number of discrepancies have been observed between experiment and leading SOL fluid codes (e.g. SOLPS), including underestimating outer target temperatures, radial electric field in the SOL, parallel ion SOL flows at the low field side, and impurity radiation. Many of these discrepancies may be linked to the fluid treatment, and might be resolved by including kinetic effects in SOL simulations.The XGCa simulation of the DIII-D tokamak in a nominally sheath-limited regime show many noteworthy features in the SOL. The density and ion temperature are higher at the low-field side, indicative of ion orbit loss. The SOL ion Mach flows are at experimentally relevant levels (Mi ∼ 0.5), with similar shapes and poloidal variation as observed in various tokamaks. Surprisingly, the ion Mach flows close to the sheath edge remain subsonic, in contrast to the typical fluid Bohm criterion requiring ion flows to be above sonic at the sheath edge. Related to this are the presence of elevated sheath potentials, eΔΦ/Te∼3−4, over most of the SOL, with regions in the near-SOL close to the separatrix having eΔΦ/Te > 4. These two results at the sheath edge are a consequence of non-Maxwellian features in the ions and electrons there.

Published
2017
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29. Mitigation of divertor heat flux by high-frequency ELM pacing with non-fuel pellet injection in DIII-D

Author

A. Bortolon, R. Maingi, D.K. Mansfield, A. Nagy, A.L. Roquemore, L.R. Baylor, N. Commaux, G.L. Jackson, R. Lunsford, C.J. Lasnier, M.J. Makowski, R. Nazikian, T.H. Osborne, and D. Shiraki

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

Experiments have been conducted on DIII-D investigating high repetition rate injection of non-fuel pellets as a tool for pacing Edge Localized Modes (ELMs) and mitigating their transient divertor heat loads. Effective ELM pacing was obtained with injection of Li granules in different H-mode scenarios, at frequencies 3–5 times larger than the natural ELM frequency, with subsequent reduction of strike-point heat flux (Bortolon et al., Nucl. Fus., 56, 056008, 2016). However, in scenarios with high pedestal density (∼6 ×1019m−3), the magnitude of granule triggered ELMs shows a broad distribution, in terms of stored energy loss and peak heat flux, challenging the effectiveness of ELM mitigation. Furthermore, transient heat-flux deposition correlated with granule injections was observed far from the strike-points. Field line tracing suggest this phenomenon to be consistent with particle loss into the mid-plane far scrape-off layer, at toroidal location of the granule injection.

Published
2017
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30. Impact of wall materials and seeding gases on the pedestal and on core plasma performance

Author

E. Wolfrum, M. Beurskens, M.G. Dunne, L. Frassinetti, X. Gao, C. Giroud, J. Hughes, T. Lunt, R. Maingi, T. Osborne, M. Reinke, and H. Urano

Subjects
Nuclear engineering. Atomic power, TK9001-9401
Abstract

Plasmas in machines with all metal plasma facing components have a lower Zeff, less radiation cooling in the scrape-off layer and divertor regions and are prone to impurity accumulation in the core. Higher gas puff and the seeding of low-Z impurities are applied to prevent impurity accumulation, to increase the frequency of edge localised modes and to cool the divertor. A lower power threshold for the transition from low-confinement mode to high confinement mode has been found in all metal wall machines when compared to carbon wall machines. The application of lithium before or during discharges can lead to ELM free H-modes. The seeding of high-Z impurities increases core radiation, reduces the power flux across the separatrix and, if applied in the right amount, does not lead to deterioration of the confinement. All these effects have in common that they can often be explained by the shape or position of the density profile. Not only the peakedness of the density profile in the core but also the position of the edge pressure gradient influences global confinement. It is shown how (i) ionisation in the pedestal region due to higher reflection of deuterium from high-Z walls, (ii) reduced recycling in consequence of lithium wall conditioning, (iii) the fostering of edge modes with lithium dropping, (iv) increased gas puff and (v) the cooling of the scrape-off layer by medium-Z impurities such as nitrogen affect the edge density profile. The consequence is a shift in the pressure profile relative to the separatrix, leading to improved pedestal stability of H-mode plasmas when the direction is inwards. Keywords: Plasma, Pedestal, Confinement, Wall material, Reflection, Lithium, Edge localised modes, Impurities, Stability

Published
2017
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32. Evaluation of a modified multipurpose cassava processing machine for size reduction

Author

Wanjala, Nasirembe, E, Rotich, R, Ruttoh, S, Nyakach, Cheboswony R, Maingi S, M, Sevu, Wanjala, Nasirembe, E, Rotich, R, Ruttoh, S, Nyakach, Cheboswony R, Maingi S, and M, Sevu

Abstract

The production of cassava (Manihot esculenta) is considered an important alternative to a reduction in food scarcity around the world. Kenya is rapidly gaining prominence due to the declining production of staple foods, especially maize and wheat. Though still considered a poor man’s food, the usage of cassava has greatly diversified in terms of both industrial and domestic applications. This coupled with the introduction of improved varieties and better farming options calls for innovative ways of handling the increasing volumes of fresh cassava tubers to minimize post-harvest losses. One of the important postharvest processes is size reduction which is achieved by either chipping or grating. Improved production methods alone are not adequate to solve the issues of field losses in cassava production. Factors affecting the efficiency of size reduction operation include operator experience, disc type, disc speed, cutting clearance and moisture content. Conventionally, this has been done manually but due to the inherent problems, the use of machines is being encouraged through the development and adoption of chipping/grating machines. In this study, the machine developed was dual-powered and allowed conversion from a chipper to a grater and vice versa as need be. It has a capacity of 162.15kg/h and 81.62 kg/h when chipping and grating respectively. The chipping process consumed less power averaging 0.0034 kW/kg compared to 0.0075 kW/kg used in the grating and these chips dried faster than manually worked cassava. Keywords: Cassava, post-harvest, chipping, grating, dual power DOI: 10.7176/ISDE/13-1-06 Publication date:June 30th 2023

Published
2023

33. Overview of Liquid-Metal PFC R&D at the University of Illinois Urbana-Champaign

Author

D. Andruczyk, R. Rizkallah, D. O’Dea, A. Shone, S. Smith, B. Kamiyama, R. Maingi, C. E. Kessel, S. Smolentsev, T. W. Morgan, and F. Romano

Subjects
Nuclear and High Energy Physics, Nuclear Energy and Engineering, Mechanical Engineering, General Materials Science, Civil and Structural Engineering
Abstract

Selected papers from the Topical Meeting on the Technology of Fusion Energy (TOFE 2022) The design and implementation of future flowing liquid-lithium plasma-facing components (LLPFCs) will be dependent on several factors. Of course, one of the most important is the need to be able to deal with high heat fluxes incident on the surface of the LLPFCs, but there are also several other important liquid-metal behaviors that have been identified for their critical impact on the feasibility of a LLPFC. One of these is the ability to constantly wet 100% of the plasma-facing component area and the best way to achieve that. Another key point is knowing and understanding the erosion and corrosion of the surfaces subject to a flowing liquid-lithium system and the ability for hydrogen and helium uptake by the system. The Center for Plasma Material Interactions (CPMI) has been tasked with looking at these various issues. The Mock-up Entry module for EAST device was used to investigate wetting and erosion effects and to design a suitable distribution and collection system with a liquid-lithium loop. The vapor shielding effects of lithium on the surface were also modeled and studied. A model coupling CRANE, an open-source global reaction network solver, and Zapdos, a plasma transport solver, is being developed to better understand the dynamics of the vapor cloud. Experiments on the Magnum-PSI at the Dutch Institute for Fundamental Energy Research have been carried out to study the vapor shielding effect and obtain experimental benchmarks to verify the model. Also, initial experiments using the Hybrid Illinois Device for Research and Applications have been performed to understand the pumping effects of lithium on helium. Experiments with a drop of liquid lithium (~100 mg) into a helium plasma have shown the ability of lithium to take out the cold recycling helium gas as well as hydrogen and oxygen impurity gases. The improvement in plasma performance was significant, and further understanding of this effect will have impacts on how future LLPFCs will be designed. Further investigation into the exact mechanism for helium pumping by lithium needs to be performed in the future. This paper presents a summary of the results obtained at the CPMI.

Published
2023
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34. DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy

Author

M. E. Fenstermacher, J. Abbate, S. Abe, T. Abrams, M. Adams, B. Adamson, N. Aiba, T. Akiyama, P. Aleynikov, E. Allen, S. Allen, H. Anand, J. Anderson, Y. Andrew, T. Andrews, D. Appelt, R. Arbon, N. Ashikawa, A. Ashourvan, M. Aslin, Y. Asnis, M. Austin, D. Ayala, J. Bak, I. Bandyopadhyay, S. Banerjee, K. Barada, L. Bardoczi, J. Barr, E. Bass, D. Battaglia, A. Battey, W. Baumgartner, L. Baylor, J. Beckers, M. Beidler, E. Belli, J. Berkery, T. Bernard, N. Bertelli, M. Beurskens, R. Bielajew, S. Bilgili, B. Biswas, S. Blondel, J. Boedo, I. Bogatu, R. Boivin, T. Bolzonella, M. Bongard, X. Bonnin, P. Bonoli, M. Bonotto, A. Bortolon, S. Bose, N. Bosviel, S. Bouwmans, M. Boyer, W. Boyes, L. Bradley, R. Brambila, D. Brennan, S. Bringuier, L. Brodsky, M. Brookman, J. Brooks, D. Brower, G. Brown, W. Brown, M. Burke, K. Burrell, K. Butler, R. Buttery, I. Bykov, P. Byrne, A. Cacheris, K. Callahan, J. Callen, G. Campbell, J. Candy, J. Canik, P. Cano-Megias, N. Cao, L. Carayannopoulos, T. Carlstrom, W. Carrig, T. Carter, W. Cary, L. Casali, M. Cengher, G. Cespedes Paz, R. Chaban, V. Chan, B. Chapman, I. Char, A. Chattopadhyay, R. Chen, J. Chen, X. Chen, M. Chen, Z. Chen, M. Choi, W. Choi, G. Choi, L. Chousal, C. Chrobak, C. Chrystal, Y. Chung, R. Churchill, M. Cianciosa, J. Clark, M. Clement, S. Coda, A. Cole, C. Collins, W. Conlin, A. Cooper, J. Cordell, B. Coriton, T. Cote, J. Cothran, A. Creely, N. Crocker, C. Crowe, B. Crowley, T. Crowley, D. Cruz-Zabala, D. Cummings, M. Curie, D. Curreli, A. Dal Molin, B. Dannels, A. Dautt-Silva, K. Davda, G. De Tommasi, P. De Vries, G. Degrandchamp, J. Degrassie, D. Demers, S. Denk, S. Depasquale, E. Deshazer, A. Diallo, S. Diem, A. Dimits, R. Ding, S. Ding, W. Ding, T. Do, J. Doane, G. Dong, D. Donovan, J. Drake, W. Drews, J. Drobny, X. Du, H. Du, V. Duarte, D. Dudt, C. Dunn, J. Duran, A. Dvorak, F. Effenberg, N. Eidietis, D. Elder, D. Eldon, R. Ellis, W. Elwasif, D. Ennis, K. Erickson, D. Ernst, M. Fasciana, D. Fedorov, E. Feibush, N. Ferraro, J. Ferreira, J. Ferron, P. Fimognari, D. Finkenthal, R. Fitzpatrick, P. Fox, W. Fox, L. Frassinetti, H. Frerichs, H. Frye, Y. Fu, K. Gage, J. Galdon Quiroga, A. Gallo, Q. Gao, A. Garcia, M. Garcia Munoz, D. Garnier, A. Garofalo, A. Gattuso, D. Geng, K. Gentle, D. Ghosh, L. Giacomelli, S. Gibson, E. Gilson, C. Giroud, F. Glass, A. Glasser, D. Glibert, P. Gohil, R. Gomez, S. Gomez, X. Gong, E. Gonzales, A. Goodman, Y. Gorelov, V. Graber, R. Granetz, T. Gray, D. Green, C. Greenfield, M. Greenwald, B. Grierson, R. Groebner, W. Grosnickle, M. Groth, H. Grunloh, S. Gu, W. Guo, H. Guo, P. Gupta, J. Guterl, W. Guttenfelder, T. Guzman, S. Haar, R. Hager, S. Hahn, M. Halfmoon, T. Hall, K. Hallatschek, F. Halpern, G. Hammett, H. Han, E. Hansen, C. Hansen, M. Hansink, J. Hanson, M. Hanson, G. Hao, A. Harris, R. Harvey, S. Haskey, E. Hassan, A. Hassanein, D. Hatch, R. Hawryluk, W. Hayashi, W. Heidbrink, J. Herfindal, J. Hicok, D. Hill, E. Hinson, C. Holcomb, L. Holland, C. Holland, E. Hollmann, J. Hollocombe, A. Holm, I. Holmes, K. Holtrop, M. Honda, R. Hong, R. Hood, A. Horton, L. Horvath, M. Hosokawa, S. Houshmandyar, N. Howard, E. Howell, D. Hoyt, W. Hu, Y. Hu, Q. Hu, J. Huang, Y. Huang, J. Hughes, T. Human, D. Humphreys, P. Huynh, A. Hyatt, C. Ibanez, L. Ibarra, R. Icasas, K. Ida, V. Igochine, Y. In, S. Inoue, A. Isayama, O. Izacard, V. Izzo, A. Jackson, G. Jacobsen, A. Jaervinen, A. Jalalvand, J. Janhunen, S. Jardin, H. Jarleblad, Y. Jeon, H. Ji, X. Jian, E. Joffrin, A. Johansen, C. Johnson, T. Johnson, C. Jones, I. Joseph, D. Jubas, B. Junge, W. Kalb, R. Kalling, C. Kamath, J. Kang, D. Kaplan, A. Kaptanoglu, S. Kasdorf, J. Kates-Harbeck, P. Kazantzidis, A. Kellman, D. Kellman, C. Kessel, K. Khumthong, E. Kim, H. Kim, J. Kim, S. Kim, K. Kim, C. Kim, W. Kimura, M. King, J. King, J. Kinsey, A. Kirk, B. Kiyan, A. Kleiner, V. Klevarova, R. Knapp, M. Knolker, W. Ko, T. Kobayashi, E. Koch, M. Kochan, B. Koel, M. Koepke, A. Kohn, R. Kolasinski, E. 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Casali, L, Cengher, M, Paz, G, Chaban, R, Chan, V, Chapman, B, Char, I, Chattopadhyay, A, Chen, R, Chen, J, Chen, X, Chen, M, Chen, Z, Choi, M, Choi, W, Choi, G, Chousal, L, Chrobak, C, Chrystal, C, Chung, Y, Churchill, R, Cianciosa, M, Clark, J, Clement, M, Coda, S, Cole, A, Collins, C, Conlin, W, Cooper, A, Cordell, J, Coriton, B, Cote, T, Cothran, J, Creely, A, Crocker, N, Crowe, C, Crowley, B, Crowley, T, Cruz-Zabala, D, Cummings, D, Curie, M, Curreli, D, Dal Molin, A, Dannels, B, Dautt-Silva, A, Davda, K, De Tommasi, G, De Vries, P, Degrandchamp, G, Degrassie, J, Demers, D, Denk, S, Depasquale, S, Deshazer, E, Diallo, A, Diem, S, Dimits, A, Ding, R, Ding, S, Ding, W, Do, T, Doane, J, Dong, G, Donovan, D, Drake, J, Drews, W, Drobny, J, Du, X, Du, H, Duarte, V, Dudt, D, Dunn, C, Duran, J, Dvorak, A, Effenberg, F, Eidietis, N, Elder, D, Eldon, D, Ellis, R, Elwasif, W, Ennis, D, Erickson, K, Ernst, D, Fasciana, M, Fedorov, D, Feibush, E, Ferraro, N, Ferreira, J, Ferron, J, Fimognari, P, Finkenthal, D, Fitzpatrick, R, Fox, P, Fox, W, Frassinetti, L, Frerichs, H, Frye, H, Fu, Y, Gage, K, Quiroga, J, Gallo, A, Gao, Q, Garcia, A, Munoz, M, Garnier, D, Garofalo, A, Gattuso, A, Geng, D, Gentle, K, Ghosh, D, Giacomelli, L, Gibson, S, Gilson, E, Giroud, C, Glass, F, Glasser, A, Glibert, D, Gohil, P, Gomez, R, Gomez, S, Gong, X, Gonzales, E, Goodman, A, Gorelov, Y, Graber, V, Granetz, R, Gray, T, Green, D, Greenfield, C, Greenwald, M, Grierson, B, Groebner, R, Grosnickle, W, Groth, M, Grunloh, H, Gu, S, Guo, W, Guo, H, Gupta, P, Guterl, J, Guttenfelder, W, Guzman, T, Haar, S, Hager, R, Hahn, S, Halfmoon, M, Hall, T, Hallatschek, K, Halpern, F, Hammett, G, Han, H, Hansen, E, Hansen, C, Hansink, M, Hanson, J, Hanson, M, Hao, G, Harris, A, Harvey, R, Haskey, S, Hassan, E, Hassanein, A, Hatch, D, Hawryluk, R, Hayashi, W, Heidbrink, W, Herfindal, J, Hicok, J, Hill, D, Hinson, E, Holcomb, C, Holland, L, Holland, C, Hollmann, E, Hollocombe, J, Holm, A, Holmes, I, Holtrop, K, Honda, M, Hong, R, Hood, R, Horton, A, Horvath, L, Hosokawa, M, Houshmandyar, S, Howard, N, Howell, E, Hoyt, D, Hu, W, Hu, Y, Hu, Q, Huang, J, Huang, Y, Hughes, J, Human, T, Humphreys, D, Huynh, P, Hyatt, A, Ibanez, C, Ibarra, L, Icasas, R, Ida, K, Igochine, V, In, Y, Inoue, S, Isayama, A, Izacard, O, Izzo, V, Jackson, A, Jacobsen, G, Jaervinen, A, Jalalvand, A, Janhunen, J, Jardin, S, Jarleblad, H, Jeon, Y, Ji, H, Jian, X, Joffrin, E, Johansen, A, Johnson, C, Johnson, T, Jones, C, Joseph, I, Jubas, D, Junge, B, Kalb, W, Kalling, R, Kamath, C, Kang, J, Kaplan, D, Kaptanoglu, A, Kasdorf, S, Kates-Harbeck, J, Kazantzidis, P, Kellman, A, Kellman, D, Kessel, C, Khumthong, K, Kim, E, Kim, H, Kim, J, Kim, S, Kim, K, Kim, C, Kimura, W, King, M, King, J, Kinsey, J, Kirk, A, Kiyan, B, Kleiner, A, Klevarova, V, Knapp, R, Knolker, M, Ko, W, Kobayashi, T, Koch, E, Kochan, M, Koel, B, Koepke, M, Kohn, A, Kolasinski, R, Kolemen, E, Kostadinova, E, Kostuk, M, Kramer, G, Kriete, D, Kripner, L, Kubota, S, Kulchar, J, Kwon, K, La Haye, R, Laggner, F, Lan, H, Lantsov, R, Lao, L, Esquisabel, A, Lasnier, C, Lau, C, Leard, B, Lee, J, Lee, R, Lee, M, Lee, Y, Lee, C, Lee, S, Lehnen, M, Leonard, A, Leppink, E, Lesher, M, Lestz, J, Leuer, J, Leuthold, N, Li, X, Li, K, Li, E, Li, G, Li, L, Li, Z, Li, J, Li, Y, Lin, Z, Lin, D, Liu, X, Liu, J, Liu, Y, Liu, T, Liu, C, Liu, Z, Liu, D, Liu, A, Loarte-Prieto, A, Lodestro, L, Logan, N, Lohr, J, Lombardo, B, Lore, J, Luan, Q, Luce, T, Di Cortemiglia, T, Luhmann, N, Lunsford, R, Luo, Z, Lvovskiy, A, Lyons, B, Ma, X, Madruga, M, Madsen, B, Maggi, C, Maheshwari, K, Mail, A, Mailloux, J, Maingi, R, Major, M, Makowski, M, Manchanda, R, Marini, C, Marinoni, A, Maris, A, Markovic, T, Marrelli, L, Martin, E, Mateja, J, Matsunaga, G, Maurizio, R, Mauzey, P, Mauzey, D, Mcardle, G, Mcclenaghan, J, Mccollam, K, Mcdevitt, C, Mckay, K, Mckee, G, Mclean, A, Mehta, V, Meier, E, Menard, J, Meneghini, O, Merlo, G, Messer, S, Meyer, W, Michael, C, Michoski, C, Milne, P, Minet, G, Misleh, A, Mitrishkin, Y, Moeller, C, Montes, K, Morales, M, Mordijck, S, Moreau, D, Morosohk, S, Morris, P, Morton, L, Moser, A, Moyer, R, Moynihan, C, Mrazkova, T, Mueller, D, Munaretto, S, Burgos, J, Murphy, C, Murphy, K, Muscatello, C, Myers, C, Nagy, A, Nandipati, G, Navarro, M, Nave, F, Navratil, G, Nazikian, R, Neff, A, Neilson, G, Neiser, T, Neiswanger, W, Nelson, D, Nelson, A, Nespoli, F, Nguyen, R, Nguyen, L, Nguyen, X, Nichols, J, Nocente, M, Nogami, S, Noraky, S, Norausky, N, Nornberg, M, Nygren, R, Odstrcil, T, Ogas, D, Ogorman, T, Ohdachi, S, Ohtani, Y, Okabayashi, M, Okamoto, M, Olavson, L, Olofsson, E, Omullane, M, Oneill, R, Orlov, D, Orvis, W, Osborne, T, Pace, D, Canal, G, Martinez, A, Palacios, L, Pan, C, Pan, Q, Pandit, R, Pandya, M, Pankin, A, Park, Y, Park, J, Parker, S, Parks, P, Parsons, M, Patel, B, Pawley, C, Paz-Soldan, C, Peebles, W, Pelton, S, Perillo, R, Petty, C, Peysson, Y, Pierce, D, Pigarov, A, Pigatto, L, Piglowski, D, Pinches, S, Pinsker, R, Piovesan, P, Piper, N, Pironti, A, Pitts, R, Pizzo, J, Plank, U, Podesta, M, Poli, E, Poli, F, Ponce, D, Popovic, Z, Porkolab, M, Porter, G, Powers, C, Powers, S, Prater, R, Pratt, Q, Pusztai, I, Qian, J, Qin, X, Ra, O, Rafiq, T, Raines, T, Raman, R, Rauch, J, Raymond, A, Rea, C, Reich, M, Reiman, A, Reinhold, S, Reinke, M, Reksoatmodjo, R, Ren, Q, Ren, Y, Ren, J, Rensink, M, Renteria, J, Rhodes, T, Rice, J, Roberts, R, Robinson, J, Fernandez, P, Rognlien, T, Rosenthal, A, Rosiello, S, Rost, J, Roveto, J, Rowan, W, Rozenblat, R, Ruane, J, Rudakov, D, Ruiz, J, Rupani, R, Saarelma, S, Sabbagh, S, Sachdev, J, Saenz, J, Saib, S, Salewski, M, Salmi, A, Sammuli, B, Samuell, C, Sandorfi, A, Sang, C, Sarff, J, Sauter, O, Schaubel, K, Schmitz, L, Schmitz, O, Schneider, J, Schroeder, P, Schultz, K, Schuster, E, Schwartz, J, Sciortino, F, Scotti, F, Scoville, J, Seltzman, A, Seol, S, Sfiligoi, I, Shafer, M, Sharapov, S, Shen, H, Sheng, Z, Shepard, T, Shi, S, Shibata, Y, Shin, G, Shiraki, D, Shousha, R, Si, H, Simmerling, P, Sinclair, G, Sinha, J, Sinha, P, Sips, G, Sizyuk, T, Skinner, C, Sladkomedova, A, Slendebroek, T, Slief, J, Smirnov, R, Smith, J, Smith, S, Smith, D, Snipes, J, Snoep, G, Snyder, A, Snyder, P, Solano, E, Solomon, W, Song, J, Sontag, A, Soukhanovskii, V, Spendlove, J, Spong, D, Squire, J, Srinivasan, C, Stacey, W, Staebler, G, Stagner, L, Stange, T, Stangeby, P, Stefan, R, Stemprok, R, Stephan, D, Stillerman, J, Stoltzfus-Dueck, T, Stonecipher, W, Storment, S, Strait, E, Su, D, Sugiyama, L, Sun, Y, Sun, P, Sun, Z, Sun, A, Sundstrom, D, Sung, C, Sungcoco, J, Suttrop, W, Suzuki, Y, Suzuki, T, Svyatkovskiy, A, Swee, C, Sweeney, R, Sweetnam, C, Szepesi, G, Takechi, M, Tala, T, Tanaka, K, Tang, X, Tang, S, Tao, Y, Tao, R, Taussig, D, Taylor, T, Teixeira, K, Teo, K, Theodorsen, A, Thomas, D, Thome, K, Thorman, A, Thornton, A, Ti, A, Tillack, M, Timchenko, N, Tinguely, R, Tompkins, R, Tooker, J, De Sousa, A, Trevisan, G, Tripathi, S, Ochoa, A, Truong, D, Tsui, C, Turco, F, Turnbull, A, Umansky, M, Unterberg, E, Vaezi, P, Vail, P, Valdez, J, Valkis, W, Van Compernolle, B, Van Galen, J, Van Kampen, R, Van Zeeland, M, Verdoolaege, G, Vianello, N, Victor, B, Viezzer, E, Vincena, S, Wade, M, Waelbroeck, F, Wai, J, Wakatsuki, T, Walker, M, Wallace, G, Waltz, R, Wampler, W, Wang, L, Wang, H, Wang, Y, Wang, Z, Wang, G, Ward, S, Watkins, M, Watkins, J, Wehner, W, Wei, Y, Weiland, M, Weisberg, D, Welander, A, White, A, White, R, Wiesen, S, Wilcox, R, Wilks, T, Willensdorfer, M, Wilson, H, Wingen, A, Wolde, M, Wolff, M, Woller, K, Wolz, A, Wong, H, Woodruff, S, Wu, M, Wu, Y, Wukitch, S, Wurden, G, Xiao, W, Xie, R, Xing, Z, Xu, X, Xu, C, Xu, G, Yan, Z, Yang, X, Yang, S, Yokoyama, T, Yoneda, R, Yoshida, M, You, K, Younkin, T, Yu, J, Yu, M, Yu, G, Yuan, Q, Zaidenberg, L, Zakharov, L, Zamengo, A, Zamperini, S, Zarnstorff, M, Zeger, E, Zeller, K, Zeng, L, Zerbini, M, Zhang, L, Zhang, X, Zhang, R, Zhang, B, Zhang, J, Zhao, L, Zhao, B, Zheng, Y, Zheng, L, Zhu, B, Zhu, J, Zhu, Y, Zsutty, M, Zuin, M, Lawrence Livermore National Laboratory, Princeton Plasma Physics Laboratory, Princeton University, General Atomics, Max-Planck-Institut für Plasmaphysik, Imperial College London, National Institute for Fusion Science, Universidade de São Paulo, University of Texas at Austin, ITER, College of William and Mary, University of California Los Angeles, University of California San Diego, Columbia University, Massachusetts Institute of Technology, Oak Ridge National Laboratory, Eindhoven University of Technology, Oak Ridge Associated Universities, West Virginia University, University of Tennessee, Knoxville, National Research Council of Italy, Stony Brook University, Purdue University, University of Seville, University of Science and Technology of China, Carnegie Mellon University, Institute for Plasma Research, Peking University, University of California Davis, University of California Irvine, Commonwealth Fusion Systems, University of Liverpool, University of Illinois at Urbana-Champaign, University of Milan - Bicocca, Georgia Institute of Technology, Southwestern Institute of Physics, University of Toronto, Auburn University, Polytechnic University of Turin, Universidade Lisboa, Association CCFE, KTH Royal Institute of Technology, San Diego State University, Durham University, Lehigh University, Fusion and Plasma Physics, University of Washington, Department of Applied Physics, Sandia National Laboratories, Ghent University, Technical University of Denmark, CEA, University of Colorado Boulder, Harvard University, National Technical University of Athens, Coventry University, University of Stuttgart, Czech Academy of Sciences, Harvey Mudd College, Seoul National University, Donghua University, University of York, Dalian University of Technology, University of California Berkeley, Los Alamos National Laboratory, United States Department of Energy, University of British Columbia, Pacific Northwest National Laboratory, University of Wisconsin, Michigan State University, University of Strathclyde, Pennsylvania State University, Rensselaer Polytechnic Institute, University of Southern California, Chalmers University of Technology, University of Virginia, University of Naples Federico II, University of Oxford, VTT Technical Research Centre of Finland, National Institute of Technology, University of Connecticut, DIFFER, CIEMAT, Hanyang University, Brigham Young University, UiT The Arctic University of Norway, Australian National University, Russian Research Centre Kurchatov Institute, Forschungszentrum Jülich, Zhejiang University, The University of Tokyo, University of Michigan, Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile, Aalto-yliopisto, Aalto University, DIII-D Team, Complex Ionized Media, Elementary Processes in Gas Discharges, Applied Physics and Science Education, Science and Technology of Nuclear Fusion, and Control Systems Technology

Subjects
Nuclear and High Energy Physics, Tokamak, Technology and Engineering, DIII-D, Nuclear engineering, TOKAMAKS, MITIGATION, law.invention, Plasma physics, mitigation, law, plasma physic, tokamak, Physics, Core-edge integration, Basis (linear algebra), plasma physics, core-edge integration, scenarios, Fusion power, Condensed Matter Physics, SCENARIOS, fusion energy, Fusion energy
Abstract

Funding Information: This material is based upon work supported by the US Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Awards DE-FC02-04ER54698 and DE-AC52-07NA27344. Publisher Copyright: © 2022 IAEA, Vienna. DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.

Published
2022
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35. ELM Suppression by Boron Powder Injection and Comparison with Lithium Powder Injection on EAST

Author

Wenbo Xu, Xianzu Gong, Erik P. Gilson, R. Maingi, D.K. Mansfield, Jin-Yong Hu, Y.Z. Qian, Kevin Tritz, Alessandro Bortolon, Mingguang Huang, Ahmed Diallo, Yu Ye, Guizhong Zuo, C.L. Li, Robert Lunsford, J. P. Qian, A. Nagy, and Zhen Sun

Subjects
Nuclear and High Energy Physics, Materials science, Divertor, chemistry.chemical_element, Plasma, Fusion power, Tungsten, Ion, Nuclear Energy and Engineering, chemistry, Nuclear fusion, Lithium, Atomic physics, Boron
Abstract

Type I edge-localized modes (ELMs) in the Experimental Advanced Superconducting Tokamak (EAST) were completely suppressed via boron powder injection into the X-point region of an upper-single null configuration over a wide range of operating conditions (2.8

Published
2020
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36. A Domestic Program for Liquid Metal PFC Research in Fusion

Author

Davide Curreli, John Canik, Bruce A. Pint, Daniel Andruczyk, C.E. Kessel, Sergey Smolentsev, Dennis L. Youchison, R. Maingi, and Egemen Kolemen

Subjects
Nuclear and High Energy Physics, Liquid metal, Tokamak, Materials science, Nuclear engineering, Divertor, Plasma, Fusion power, law.invention, Nuclear Energy and Engineering, law, Nuclear fusion, Engineering design process, Plasma-facing material
Abstract

While high-Z solid plasma-facing components (PFCs) are the leading candidates for reactors, it is unclear that they can survive the intense plasma material interaction (PMI). Liquid metals (LM) PFCs offer potential solutions since they are not susceptible to the same type of damage, and can be “self-healing”. Following the Fusion Energy System Study on Liquid Metal Plasma Facing Components study that recently was completed by Kessel et al. (Fusion Sci Technnol 75:886, 2019) a domestic LM PFC design program has been initiated to develop reactor-relevant LM PFC concepts. This program seeks to evaluate LM PFC concepts for a Fusion Nuclear Science Facility (FNSF) or a Compact Pilot Plant via engineering design calculations, modeling of PMI and PFC components and laboratory experiments. The latter involves experiments in dedicated test stands and confinement devices and seeks to identify and answer open questions in LM PFC design. The new national LM PFC program is first investigating lithium as the plasma facing material for a flowing divertor PFC concept. Several flow speeds will be evaluated, ranging from ~ cm/s to m/s. The surface temperature will initially be held below the strongly evaporative limit in the first design; higher temperatures with strong evaporation will be considered in future concepts. Other topics of interest include: understanding of the hydrogen and helium interaction with the liquid lithium; single effect experiments on wetting, compatibility and embrittlement; and prototypical experiments for control and characterization of flowing LM. A path to plasma and future tokamak exposure of these concepts will be developed.

Published
2020
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37. Mitigation of plasma-wall interactions with low-Z powders in DIII-D high confinement plasmas

Author

F. Effenberg, A. Bortolon, L. Casali, R. Nazikian, I. Bykov, F. Scotti, H.Q. Wang, M.E. Fenstermacher, R. Lunsford, A. Nagy, B.A. Grierson, F.M. Laggner, R. Maingi, and null the DIII-D Team

Subjects
Plasma Physics (physics.plasm-ph), Nuclear and High Energy Physics, FOS: Physical sciences, Physics - Applied Physics, Applied Physics (physics.app-ph), Condensed Matter Physics, Physics - Plasma Physics
Abstract

Experiments with low-Z powder injection in DIII-D high confinement discharges demonstrated increased divertor dissipation and detachment while maintaining good core energy confinement. Lithium (Li), boron (B), and boron nitride (BN) powders were injected in high-confinement mode plasmas ($I_p=$1 MA, $B_t=$2 T, $P_{NB}=$6 MW, $\langle n_e\rangle=3.6-5.0\cdot10^{19}$ m$^{-3}$) into the upper small-angle slot (SAS) divertor for 2-s intervals at constant rates of 3-204 mg/s. The multi-species BN powders at a rate of 54 mg/s showed the most substantial increase in divertor neutral compression by more than an order of magnitude and lasting detachment with minor degradation of the stored magnetic energy $W_{mhd}$ by 5%. Rates of 204 mg/s of boron nitride powder further reduce ELM-fluxes on the divertor but also cause a drop in confinement performance by 24% due to the onset of an $n=2$ tearing mode. The application of powders also showed a substantial improvement of wall conditions manifesting in reduced wall fueling source and intrinsic carbon and oxygen content in response to the cumulative injection of non-recycling materials. The results suggest that low-Z powder injection, including mixed element compounds, is a promising new core-edge compatible technique that simultaneously enables divertor detachment and improves wall conditions during high confinement operation., Comment: F. Effenberg et al 2022 Nucl. Fusion in press https://doi.org/10.1088/1741-4326/ac899d

Published
2022
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38. Progress from ASDEX Upgrade experiments in preparing the physics basis of ITER operation and DEMO scenario development

Author

U. Stroth, D. Aguiam, E. Alessi, C. Angioni, N. Arden, R. Arredondo Parra, V. Artigues, O. Asunta, M. Balden, V. Bandaru, A. Banon-Navarro, K. Behler, A. Bergmann, M. Bergmann, J. Bernardo, M. Bernert, A. Biancalani, R. Bielajew, R. Bilato, G. Birkenmeier, T. Blanken, V. Bobkov, A. Bock, T. Body, T. Bolzonella, N. Bonanomi, A. Bortolon, B. Böswirth, C. Bottereau, A. Bottino, H. van den Brand, M. Brenzke, S. Brezinsek, D. Brida, F. Brochard, C. Bruhn, J. Buchanan, A. Buhler, A. Burckhart, Y. Camenen, B. Cannas, P. Cano Megias, D. Carlton, M. Carr, P. Carvalho, C. Castaldo, M. Cavedon, C. Cazzaniga, C. Challis, A. Chankin, C. Cianfarani, F. Clairet, S. Coda, R. Coelho, J.W. Coenen, L. Colas, G. Conway, S. Costea, D. Coster, T. Cote, A.J. Creely, G. Croci, D.J. Cruz Zabala, G. Cseh, A. Czarnecka, I. Cziegler, O. D’Arcangelo, A. Dal Molin, P. David, C. Day, M. de Baar, P. de Marné, R. Delogu, S. Denk, P. Denner, A. Di Siena, J.J. Dominguez Palacios Durán, D. Dunai, A. Drenik, M. Dreval, R. Drube, M. Dunne, B.P. Duval, R. Dux, T. Eich, S. Elgeti, A. Encheva, K. Engelhardt, B. Erdös, I. Erofeev, B. Esposito, E. Fable, M. Faitsch, U. Fantz, M. Farnik, H. Faugel, F. Felici, O. Ficker, S. Fietz, A. Figueredo, R. Fischer, O. Ford, L. Frassinetti, M. Fröschle, G. Fuchert, J.C. Fuchs, H. Fünfgelder, S. Futatani, K. Galazka, J. Galdon-Quiroga, D. Gallart Escolà, A. Gallo, Y. Gao, S. Garavaglia, M. Garcia Muñoz, B. Geiger, L. Giannone, S. Gibson, L. Gil, E. Giovannozzi, S. Glöggler, M. Gobbin, J. Gonzalez Martin, T. Goodman, G. Gorini, T. Görler, D. Gradic, G. Granucci, A. Gräter, H. Greuner, M. Griener, M. Groth, A. Gude, L. Guimarais, S. Günter, G. Haas, A.H. Hakola, C. Ham, T. Happel, N. den Harder, G. Harrer, J. Harrison, V. Hauer, T. Hayward-Schneider, B. Heinemann, T. Hellsten, S. Henderson, P. Hennequin, A. Herrmann, E. Heyn, F. Hitzler, J. Hobirk, K. Höfler, J.H. Holm, M. Hölzl, C. Hopf, L. Horvath, T. Höschen, A. Houben, A. Hubbard, A. Huber, K. Hunger, V. Igochine, M. Iliasova, T. Ilkei, K. Insulander Björk, C. Ionita-Schrittwieser, I. Ivanova-Stanik, W. Jacob, N. Jaksic, F. Janky, A. Jansen van Vuuren, A. Jardin, F. Jaulmes, F. Jenko, T. Jensen, E. Joffrin, A. Kallenbach, S. Kálvin, M. Kantor, A. Kappatou, O. Kardaun, J. Karhunen, C.-P. Käsemann, S. Kasilov, A. Kendl, W. Kernbichler, E. Khilkevitch, A. Kirk, S. Kjer Hansen, V. Klevarova, G. Kocsis, M. Koleva, M. Komm, M. Kong, A. Krämer-Flecken, K. Krieger, A. Krivska, O. Kudlacek, T. Kurki-Suonio, B. Kurzan, B. Labit, K. Lackner, F. Laggner, A. Lahtinen, P.T. Lang, P. Lauber, N. Leuthold, L. Li, J. Likonen, O. Linder, B. Lipschultz, Y. Liu, A. Lohs, Z. Lu, T. Luda di Cortemiglia, N.C. Luhmann, T. Lunt, A. Lyssoivan, T. Maceina, J. Madsen, A. Magnanimo, H. Maier, J. Mailloux, R. Maingi, O. Maj, E. Maljaars, P. Manas, A. Mancini, A. Manhard, P. Mantica, M. Mantsinen, P. Manz, M. Maraschek, C. Marchetto, L. Marrelli, P. Martin, A. Martitsch, F. Matos, M. Mayer, M.-L. Mayoral, D. Mazon, P.J. McCarthy, R. McDermott, R. Merkel, A. Merle, D. Meshcheriakov, H. Meyer, D. Milanesio, P. Molina Cabrera, F. Monaco, M. Muraca, F. Nabais, V. Naulin, R. Nazikian, R.D. Nem, A. Nemes-Czopf, G. Neu, R. Neu, A.H. Nielsen, S.K. Nielsen, T. Nishizawa, M. Nocente, J.-M. Noterdaeme, I. Novikau, S. Nowak, M. Oberkofler, R. Ochoukov, J. Olsen, F. Orain, F. Palermo, O. Pan, G. Papp, I. Paradela Perez, A. Pau, G. Pautasso, C. Paz-Soldan, P. Petersson, P. Piovesan, C. Piron, U. Plank, B. Plaum, B. Plöck, V. Plyusnin, G. Pokol, E. Poli, L. Porte, T. Pütterich, M. Ramisch, J. Rasmussen, G. Ratta, S. Ratynskaia, G. Raupp, D. Réfy, M. Reich, F. Reimold, D. Reiser, M. Reisner, D. Reiter, T. Ribeiro, R. Riedl, J. Riesch, D. Rittich, J.F. Rivero Rodriguez, G. Rocchi, P. Rodriguez-Fernandez, M. Rodriguez-Ramos, V. Rohde, G. Ronchi, A. Ross, M. Rott, M. Rubel, D.A. Ryan, F. Ryter, S. Saarelma, M. Salewski, A. Salmi, O. Samoylov, L. Sanchis Sanchez, J. Santos, O. Sauter, G. Schall, K. Schlüter, K. Schmid, O. Schmitz, P.A. Schneider, R. Schrittwieser, M. Schubert, C. Schuster, T. Schwarz-Selinger, J. Schweinzer, E. Seliunin, A. Shabbir, A. Shalpegin, S. Sharapov, U. Sheikh, A. Shevelev, G. Sias, M. Siccinio, B. Sieglin, A. Sigalov, A. Silva, C. Silva, D. Silvagni, J. Simpson, S. Sipilä, E. Smigelskis, A. Snicker, E. Solano, C. Sommariva, C. Sozzi, G. Spizzo, M. Spolaore, A. Stegmeir, M. Stejner, J. Stober, E. Strumberge, G. Suarez Lopez, H.-J. Sun, W. Suttrop, E. Sytova, T. Szepesi, B. Tál, T. Tala, G. Tardini, M. Tardocchi, D. Terranova, M. Teschke, E. Thorén, W. Tierens, D. Told, W. Treutterer, G. Trevisan, E. Trier, M. Tripský, M. Usoltceva, M. Valisa, M. Valovic, M. van Zeeland, F. Vannini, B. Vanovac, P. Varela, S. Varoutis, N. Vianello, J. Vicente, G. Verdoolaege, T. Vierle, E. Viezzer, I. Voitsekhovitch, U. von Toussaint, D. Wagner, X. Wang, M. Weiland, A.E. White, M. Willensdorfer, B. Wiringer, M. Wischmeier, R. Wolf, E. Wolfrum, Q. Yang, Q. Yu, R. Zagórski, I. Zammuto, T. Zehetbauer, W. Zhang, W. Zholobenko, M. Zilker, A. Zito, H. Zohm, S. Zoletnik, the EUROfusion MST1 Team, Max-Planck-Institut für Plasmaphysik [Garching] (IPP), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Aix Marseille Université (AMU), Laboratoire de Physique des Plasmas (LPP), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), EUROfusion MST1 Team, Barcelona Supercomputing Center, Department of Applied Physics, Aalto-yliopisto, Aalto University, Stroth, U, Aguiam, D, Alessi, E, Angioni, C, Arden, N, Parra, R, Artigues, V, Asunta, O, Balden, M, Bandaru, V, Banon-Navarro, A, Behler, K, Bergmann, A, Bergmann, M, Bernardo, J, Bernert, M, Biancalani, A, Bielajew, R, Bilato, R, Birkenmeier, G, Blanken, T, Bobkov, V, Bock, A, Body, T, Bolzonella, T, Bonanomi, N, Bortolon, A, Boswirth, B, Bottereau, C, Bottino, A, Van Den Brand, H, Brenzke, M, Brezinsek, S, Brida, D, Brochard, F, Bruhn, C, Buchanan, J, Buhler, A, Burckhart, A, Camenen, Y, Cannas, B, Megias, P, Carlton, D, Carr, M, Carvalho, P, Castaldo, C, Cavedon, M, Cazzaniga, C, Challis, C, Chankin, A, Cianfarani, C, Clairet, F, Coda, S, Coelho, R, Coenen, J, Colas, L, Conway, G, Costea, S, Coster, D, Cote, T, Creely, A, Croci, G, Zabala, D, Cseh, G, Czarnecka, A, Cziegler, I, D'Arcangelo, O, Molin, A, David, P, Day, C, De Baar, M, De Marne, P, Delogu, R, Denk, S, Denner, P, Di Siena, A, Palacios Duran, J, Dunai, D, Drenik, A, Dreval, M, Drube, R, Dunne, M, Duval, B, Dux, R, Eich, T, Elgeti, S, Encheva, A, Engelhardt, K, Erdos, B, Erofeev, I, Esposito, B, Fable, E, Faitsch, M, Fantz, U, Farnik, M, Faugel, H, Felici, F, Ficker, O, Fietz, S, Figueredo, A, Fischer, R, Ford, O, Frassinetti, L, Froschle, M, Fuchert, G, Fuchs, J, Funfgelder, H, Futatani, S, Galazka, K, Galdon-Quiroga, J, Escola, D, Gallo, A, Gao, Y, Garavaglia, S, Munoz, M, Geiger, B, Giannone, L, Gibson, S, Gil, L, Giovannozzi, E, Gloggler, S, Gobbin, M, Martin, J, Goodman, T, Gorini, G, Gorler, T, Gradic, D, Granucci, G, Grater, A, Greuner, H, Griener, M, Groth, M, Gude, A, Guimarais, L, Gunter, S, Haas, G, Hakola, A, Ham, C, Happel, T, Den Harder, N, Harrer, G, Harrison, J, Hauer, V, Hayward-Schneider, T, Heinemann, B, Hellsten, T, Henderson, S, Hennequin, P, Herrmann, A, Heyn, E, Hitzler, F, Hobirk, J, Hofler, K, Holm, J, Holzl, M, Hopf, C, Horvath, L, Hoschen, T, Houben, A, Hubbard, A, Huber, A, Hunger, K, Igochine, V, Iliasova, M, Ilkei, T, Bjork, K, Ionita-Schrittwieser, C, Ivanova-Stanik, I, Jacob, W, Jaksic, N, Janky, F, Jansen Van Vuuren, A, Jardin, A, Jaulmes, F, Jenko, F, Jensen, T, Joffrin, E, Kallenbach, A, Kalvin, S, Kantor, M, Kappatou, A, Kardaun, O, Karhunen, J, Kasemann, C, Kasilov, S, Kendl, A, Kernbichler, W, Khilkevitch, E, Kirk, A, Hansen, S, Klevarova, V, Kocsis, G, Koleva, M, Komm, M, Kong, M, Kramer-Flecken, A, Krieger, K, Krivska, A, Kudlacek, O, Kurki-Suonio, T, Kurzan, B, Labit, B, Lackner, K, Laggner, F, Lahtinen, A, Lang, P, Lauber, P, Leuthold, N, Li, L, Likonen, J, Linder, O, Lipschultz, B, Liu, Y, Lohs, A, Lu, Z, Luda Di Cortemiglia, T, Luhmann, N, Lunt, T, Lyssoivan, A, Maceina, T, Madsen, J, Magnanimo, A, Maier, H, Mailloux, J, Maingi, R, Maj, O, Maljaars, E, Manas, P, Mancini, A, Manhard, A, Mantica, P, Mantsinen, M, Manz, P, Maraschek, M, Marchetto, C, Marrelli, L, Martin, P, Martitsch, A, Matos, F, Mayer, M, Mayoral, M, Mazon, D, Mccarthy, P, Mcdermott, R, Merkel, R, Merle, A, Meshcheriakov, D, Meyer, H, Milanesio, D, Cabrera, P, Monaco, F, Muraca, M, Nabais, F, Naulin, V, Nazikian, R, Nem, R, Nemes-Czopf, A, Neu, G, Neu, R, Nielsen, A, Nielsen, S, Nishizawa, T, Nocente, M, Noterdaeme, J, Novikau, I, Nowak, S, Oberkofler, M, Ochoukov, R, Olsen, J, Orain, F, Palermo, F, Pan, O, Papp, G, Perez, I, Pau, A, Pautasso, G, Paz-Soldan, C, Petersson, P, Piovesan, P, Piron, C, Plank, U, Plaum, B, Plock, B, Plyusnin, V, Pokol, G, Poli, E, Porte, L, Putterich, T, Ramisch, M, Rasmussen, J, Ratta, G, Ratynskaia, S, Raupp, G, Refy, D, Reich, M, Reimold, F, Reiser, D, Reisner, M, Reiter, D, Ribeiro, T, Riedl, R, Riesch, J, Rittich, D, Rodriguez, J, Rocchi, G, Rodriguez-Fernandez, P, Rodriguez-Ramos, M, Rohde, V, Ronchi, G, Ross, A, Rott, M, Rubel, M, Ryan, D, Ryter, F, Saarelma, S, Salewski, M, Salmi, A, Samoylov, O, Sanchez, L, Santos, J, Sauter, O, Schall, G, Schluter, K, Schmid, K, Schmitz, O, Schneider, P, Schrittwieser, R, Schubert, M, Schuster, C, Schwarz-Selinger, T, Schweinzer, J, Seliunin, E, Shabbir, A, Shalpegin, A, Sharapov, S, Sheikh, U, Shevelev, A, Sias, G, Siccinio, M, Sieglin, B, Sigalov, A, Silva, A, Silva, C, Silvagni, D, Simpson, J, Sipila, S, Smigelskis, E, Snicker, A, Solano, E, Sommariva, C, Sozzi, C, Spizzo, G, Spolaore, M, Stegmeir, A, Stejner, M, Stober, J, Strumberge, E, Lopez, G, Sun, H, Suttrop, W, Sytova, E, Szepesi, T, Tal, B, Tala, T, Tardini, G, Tardocchi, M, Terranova, D, Teschke, M, Thoren, E, Tierens, W, Told, D, Treutterer, W, Trevisan, G, Trier, E, Tripsky, M, Usoltceva, M, Valisa, M, Valovic, M, Van Zeeland, M, Vannini, F, Vanovac, B, Varela, P, Varoutis, S, Vianello, N, Vicente, J, Verdoolaege, G, Vierle, T, Viezzer, E, Voitsekhovitch, I, Von Toussaint, U, Wagner, D, Wang, X, Weiland, M, White, A, Willensdorfer, M, Wiringer, B, Wischmeier, M, Wolf, R, Wolfrum, E, Yang, Q, Yu, Q, Zagorski, R, Zammuto, I, Zehetbauer, T, Zhang, W, Zholobenko, W, Zilker, M, Zito, A, Zohm, H, and Zoletnik, S

Subjects
Nuclear and High Energy Physics, Asdex Upgrade, confinement, ELLM-free discharges, sol, Computer science, Nuclear engineering, ALCATOR C-MOD, UPPER DIVERTOR, ASDEX Upgrade, Physics::Plasma Physics, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Simulació per ordinador, alcator c-mod, ddc:530, upper divertor, ELLM-free discharge, SOL, Basis (linear algebra), Physics, turbulence, transition, h-mode plasmas, Condensed Matter Physics, ddc, Informàtica::Aplicacions de la informàtica::Aplicacions informàtiques a la física i l‘enginyeria [Àrees temàtiques de la UPC], Fusion reactors, Physics and Astronomy, CONFINEMENT MODES, H-MODE PLASMAS, Physics::Space Physics, Nuclear fusion, TURBULENCE, ddc:620, confinement modes, TRANSITION
Abstract

An overview of recent results obtained at the tokamak ASDEX Upgrade (AUG) is given. A work flow for predictive profile modelling of AUG discharges was established which is able to reproduce experimental H-mode plasma profiles based on engineering parameters only. In the plasma center, theoretical predictions on plasma current redistribution by a dynamo effect were confirmed experimentally. For core transport, the stabilizing effect of fast ion distributions on turbulent transport is shown to be important to explain the core isotope effect and improves the description of hollow low-Z impurity profiles. The L–H power threshold of hydrogen plasmas is not affected by small helium admixtures and it increases continuously from the deuterium to the hydrogen level when the hydrogen concentration is raised from 0 to 100%. One focus of recent campaigns was the search for a fusion relevant integrated plasma scenario without large edge localised modes (ELMs). Results from six different ELM-free confinement regimes are compared with respect to reactor relevance: ELM suppression by magnetic perturbation coils could be attributed to toroidally asymmetric turbulent fluctuations in the vicinity of the separatrix. Stable improved confinement mode plasma phases with a detached inner divertor were obtained using a feedback control of the plasma β. The enhanced Dα H-mode regime was extended to higher heating power by feedback controlled radiative cooling with argon. The quasi-coherent exhaust regime was developed into an integrated scenario at high heating power and energy confinement, with a detached divertor and without large ELMs. Small ELMs close to the separatrix lead to peeling-ballooning stability and quasi continuous power exhaust. Helium beam density fluctuation measurements confirm that transport close to the separatrix is important to achieve the different ELM-free regimes. Based on separatrix plasma parameters and interchange-drift-Alfvén turbulence, an analytic model was derived that reproduces the experimentally found important operational boundaries of the density limit and between L- and H-mode confinement. Feedback control for the X-point radiator (XPR) position was established as an important element for divertor detachment control. Stable and detached ELM-free phases with H-mode confinement quality were obtained when the XPR was moved 10 cm above the X-point. Investigations of the plasma in the future flexible snow-flake divertor of AUG by means of first SOLPS-ITER simulations with drifts activated predict beneficial detachment properties and the activation of an additional strike point by the drifts. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Peer Reviewed "Article signat per més de 50 autors/es: U. Stroth, D. Aguiam, E. Alessi, C. Angioni, N. Arden, R. Arredondo Parra, V. Artigues, O. Asunta, M. Balden, V. Bandaru, A. Banon-Navarro, K. Behler, A. Bergmann, M. Bergmann, J. Bernardo, M. Bernert, A. Biancalani, R. Bielajew, R. Bilato, G. Birkenmeier, T. Blanken, V. Bobkov, A. Bock, T. Body, T. Bolzonella, N. Bonanomi, A. Bortolon, B. Böswirth, C. Bottereau, A. Bottino, H. van den Brand, M. Brenzke, S. Brezinsek, D. Brida, F. Brochard, C. Bruhn, J. Buchanan, A. Buhler, A. Burckhart, Y. Camenen, B. Cannas, P. Cano Megias, D. Carlton, M. Carr, P. Carvalho, C. Castaldo, M. Cavedon, C. Cazzaniga, C. Challis, A. Chankin, C. Cianfarani, F. Clairet, S. Coda, R. Coelho, J.W. Coenen, L. Colas, G. Conway, S. Costea, D. Coster, T. Cote, A.J. Creely, G. Croci, D.J. Cruz Zabala, G. Cseh, A. Czarnecka, I. Cziegler, O. D'Arcangelo, A. Dal Molin, P. David, C. Day, M. de Baar, P. de Marné, R. Delogu, S. Denk, P. Denner, A. Di Siena, J.J. Dominguez Palacios Durán, D. Dunai, A. Drenik, M. Dreval, R. Drube, M. Dunne, B.P. Duval, R. Dux, T. Eich, S. Elgeti, A. Encheva, K. Engelhardt, B. Erdös, I. Erofeev, B. Esposito, E. Fable, M. Faitsch, U. Fantz, M. Farnik, H. Faugel, F. Felici, O. Ficker, S. Fietz, A. Figueredo, R. Fischer, O. Ford, L. Frassinetti, M. Fröschle, G. Fuchert, J.C. Fuchs, H. Fünfgelder, S. Futatani, K. Galazka, J. Galdon-Quiroga, D. Gallart Escolà, A. Gallo10, Y. Gao11, S. Garavaglia3, M. Garcia Muñoz16, B. Geiger21, L. Giannone1, S. Gibson32, L. Gil2, E. Giovannozzi18, S. Glöggler1, M. Gobbin8, J. Gonzalez Martin, T. Goodman, G. Gorini, T. Görler, D. Gradic, G. Granucci, A. Gräter, H. Greuner, M. Griener, M. Groth, A. Gude, L. Guimarais, S. Günter, G. Haas, A.H. Hakola, C. Ham, T. Happel, N. den Harder, G. Harrer, J. Harrison, V. Hauer, T. Hayward-Schneider, B. Heinemann, T. Hellsten, S. Henderson, P. Hennequin, A. Herrmann, E. Heyn, F. Hitzler, J. Hobirk, K. Höfler, J.H. Holm, M. Hölzl, C. Hopf, L. Horvath, T. Höschen, A. Houben, A. Hubbard, A. Huber, K. Hunger, V. Igochine, M. Iliasova, T. Ilkei, K. Insulander Björk, C. Ionita-Schrittwieser, I. Ivanova-Stanik, W. Jacob, N. Jaksic, F. Janky, A. Jansen van Vuuren, A. Jardin, F. Jaulmes, F. Jenko, T. Jensen, E. Joffrin, A. Kallenbach, S. Kálvin, M. Kantor, A. Kappatou, O. Kardaun, J. Karhunen4, C.-P. Käsemann, S. Kasilov, A. Kendl, W. Kernbichler, E. Khilkevitch, A. Kirk, S. Kjer Hansen, V. Klevarova, G. Kocsis, M. Koleva, M. Komm, M. Kong, A. Krämer-Flecken, K. Krieger, A. Krivska, O. Kudlacek, T. Kurki-Suonio, B. Kurzan, B. Labit, K. Lackner, F. Laggner, A. Lahtinen, P.T. Lang, P. Lauber, N. Leuthold, L. Li, J. Likonen, O. Linder, B. Lipschultz, Y. Liu, A. Lohs, Z. Lu, T. Luda di Cortemiglia, N.C. Luhmann, T. Lunt, A. Lyssoivan, T. Maceina, J. Madsen, A. Magnanimo, H. Maier, J. Mailloux, R. Maingi, O. Maj, E. Maljaars, P. Manas, A. Mancini, A. Manhard, P. Mantica, M. Mantsinen, P. Manz, M. Maraschek, C. Marchetto, L. Marrelli, P. Martin, A. Martitsch, F. Matos, M. Mayer, M.-L. Mayoral, D. Mazon, P.J. McCarthy, R. McDermott, R. Merkel, A. Merle, D. Meshcheriakov, H. Meyer, D. Milanesio, P. Molina Cabrera, F. Monaco, M. Muraca, F. Nabais, V. Naulin, R. Nazikian, R.D. Nem, A. Nemes-Czopf, G. Neu, R. Neu, A.H. Nielsen, S.K. Nielsen, T. Nishizawa, M. Nocente, J.-M. Noterdaeme, I. Novikau, S. Nowak, M. Oberkofler, R. Ochoukov, J. Olsen, F. Orain, F. Palermo, O. Pan, G. Papp, I. Paradela Perez, A. Pau, G. Pautasso, C. Paz-Soldan, P. Petersson, P. Piovesan, C. Piron, U. Plank, B. Plaum, B. Plöck, V. Plyusnin, G. Pokol, E. Poli, L. Porte, T. Pütterich, M. Ramisch, J. Rasmussen, G. Ratta, S. Ratynskaia, G. Raupp, D. Réfy, M. Reich1, F. Reimold, D. Reiser, M. Reisner, D. Reiter, T. Ribeiro, R. Riedl, J. Riesch, D. Rittich, J.F. Rivero Rodriguez, G. Rocchi, P. Rodriguez-Fernandez, M. Rodriguez-Ramos, V. Rohde, G. Ronchi, A. Ross, M. Rott, M. Rubel, D.A. Ryan, F. Ryter, S. Saarelma, M. Salewski, A. Salmi, O. Samoylov, L. Sanchis Sanchez, J. Santos, O. Sauter, G. Schall, K. Schlüter, K. Schmid, O. Schmitz, P.A. Schneider, R. Schrittwieser, M. Schubert, C. Schuster, T. Schwarz-Selinger, J. Schweinzer, E. Seliunin, A. Shabbir, A. Shalpegin, S. Sharapov, U. Sheikh, A. Shevelev, G. Sias, M. Siccinio, B. Sieglin, A. Sigalov, A. Silva, C. Silva, D. Silvagni, J. Simpson, S. Sipilä, E. Smigelskis, A. Snicker, E. Solano, C. Sommariva, C. Sozzi, G. Spizzo, M. Spolaore, A. Stegmeir, M. Stejner, J. Stober, E. Strumberge1, G. Suarez Lopez, H.-J. Sun, W. Suttrop, E. Sytova, T. Szepesi, B. Tál, T. Tala, G. Tardini, M. Tardocchi, D. Terranova, M. Teschke, E. Thorén, W. Tierens, D. Told, W. Treutterer, G. Trevisan, E. Trier, M. Tripský, M. Usoltceva, M. Valisa, M. Valovic, M. van Zeeland, F. Vannini, B. Vanovac, P. Varela, S. Varoutis, N. Vianello, J. Vicente, G. Verdoolaege, T. Vierle, E. Viezzer, I. Voitsekhovitch, U. von Toussaint, D. Wagner, X. Wang, M. Weiland, A.E. White, M. Willensdorfer, B. Wiringer, M. Wischmeier, R. Wolf, E. Wolfrum, Q. Yang, Q. Yu, R. Zagórski, I. Zammuto, T. Zehetbauer, W. Zhang, W. Zholobenko, M. Zilker, A. Zito, H. Zohm, S. Zoletnik and the EUROfusion MST1 Team "

Published
2022
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39. Wall conditioning and ELM mitigation with boron nitride powder injection in KSTAR

Author

Inwoo Song, R. Maingi, A. Nagy, Wonho Choe, S. W. Yoon, Jonghyun Lee, Suk-Ho Hong, Seongchong Park, Erik P. Gilson, Alessandro Bortolon, Hyunyong Lee, Ahmed Diallo, J. I. Song, H. H. Lee, D.K. Mansfield, S. W. Yun, and Raffi Nazikian

Subjects
Nuclear and High Energy Physics, Materials science, Materials Science (miscellaneous), TK9001-9401, Analytical chemistry, Edge-localized mode, Plasma, Powder injection, Boron nitride, Plasma flow, chemistry.chemical_compound, Nuclear Energy and Engineering, chemistry, Impurity, KSTAR, Wall conditioning, Conditioning, Nuclear engineering. Atomic power, ELM
Abstract

Results from KSTAR powder injection experiments, in which tens of milligrams of boron nitride (BN) were dropped into low-power H-mode plasmas, show an improvement in wall conditions in subsequent discharges and, in some cases, a reduction or elimination of edge-localized modes (ELMs). Injected powder is distributed by the plasma flow and is deposited on the wall and, over the course of several discharges, was observed to gradually reduce recycling by 33%, and decrease both the ELM amplitude and frequency. This is the first demonstration of the use of BN for ELM mitigation. In all of these experiments, an Impurity Powder Dropper (IPD) was used to introduce precise, controllable amounts of the materials into ELMy H-mode KSTAR discharges. The plasma duration was between 10 s and 15 s, I p = 500 kA, B T = 1 . 8 T, P NBI = 1 . 6 MW, and P ECH = 0 . 6 MW. Plasma densities were between 2 and 3 × 1 0 19 m−3. In all cases, the pre-fill and startup gas-fueling was kept constant, suggesting that the decrease in baseline D α emission is in fact due to a reduction in recycling. The results presented herein highlight the viability of powder injection for intra-shot and between-shot wall conditioning.

Published
2021

40. Deuterium pellet fueling in type-III ELMy H-mode plasmas on EAST superconducting tokamak

Author

Yumin Wang, Chen Yue, R. Maingi, Haiqing Liu, Jiangang Li, Qing Zang, Jilei Hou, Hailin Zhao, Kevin Tritz, Erik P. Gilson, Jichan Xu, Zhen Sun, Xiaolin Yuan, and Jiansheng Hu

Subjects
Electron density, Tokamak, Materials science, Mechanical Engineering, Nuclear engineering, Pellets, Plasma, Fusion power, 01 natural sciences, 010305 fluids & plasmas, law.invention, Superconducting tokamak, Nuclear Energy and Engineering, Deuterium, law, 0103 physical sciences, Pellet, General Materials Science, 010306 general physics, Civil and Structural Engineering
Abstract

Type-III ELMy H-mode plasmas are a valuable operating scenario, as they may simultaneously achieve fusion power gain of Q = 10 and acceptable steady-state and peak power fluxes to the plasma-facing components. It is important to investigate cryogenic deuterium pellet injection fueling in this kind of H-mode plasma since it has been chosen as a main plasma fueling technique for ITER. Recently, pellet fueling experiments have been successfully carried out on EAST, an ITER-like tokamak. A maximum electron density of 0.73 × nGW has been obtained. It is found that ELM behavior was modified immediately and a string of small ELMs were induced when pellets were injected at a low velocity from ˜40 cm above the mid-plane on the low field side, which is different from the fact that pellets trigger signal ELMs in Type-I ELMy H-mode plasmas in other tokamaks. The decreased edge temperature caused by the cryogenic pellet was proposed as the reason for this ELM modification. These results will provide a useful reference for the pellet fueling in a Type-III ELMy H-mode plasma on ITER in the future.

Published
2019
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41. Study of the Impact of Pre- and Real-Time Depositions of Lithium on Plasma Performance on NSTX

Author

Stanley Kaye, G. P. Canal, Todd Evans, D.K. Mansfield, and R. Maingi

Subjects
Nuclear and High Energy Physics, Materials science, Divertor, Nuclear engineering, Evaporation, chemistry.chemical_element, Plasma, Edge (geometry), Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, chemistry, 0103 physical sciences, Lithium, National Spherical Torus Experiment
Abstract

The efficiency of two lithium (Li) injection methods used on the National Spherical Torus Experiment (NSTX) are compared in terms of the amount of Li used to produce equivalent plasma performance improvements, namely, Li evaporation over the divertor plates, prior to the initiation of the discharge, and real-time Li injection directly into the plasma scrape-off layer during the discharge. The measurements show that the real-time method can affect the energy confinement and the edge stability of NSTX plasmas in a more efficient way than the Li evaporation method, as it requires only a fraction of the amount of Li used by the evaporation method to produce similar improvements.

Published
2019
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42. Supplemental ELM control in ITER through beryllium granule injection

Author

A. Nagy, D.K. Mansfield, Robert Lunsford, R. Maingi, Tamsin Osborne, G.L. Jackson, and Alessandro Bortolon

Subjects
010302 applied physics, Nuclear and High Energy Physics, Materials science, Pellet size, Materials Science (miscellaneous), Nuclear engineering, Granule (cell biology), Pellets, chemistry.chemical_element, Plasma, 01 natural sciences, lcsh:TK9001-9401, 010305 fluids & plasmas, Nuclear Energy and Engineering, chemistry, Impurity, 0103 physical sciences, Electromagnetic shielding, Pellet, lcsh:Nuclear engineering. Atomic power, Beryllium
Abstract

Injection of low-Z granules into high performance discharges on DIII-D has been shown to promptly trigger Edge Localized Modes (ELMs) providing high-Z impurity control without significant plasma degradation. The ability to provide ELM triggering over a range of injection and discharge parameters suggests that the mechanical introduction of granules can be considered as an additional method of impurity control in ITER. Utilizing a spherically symmetric vapor shielding model for granule ablation, benchmarked with impurity granule injections on DIII-D, we simulate the injection of beryllium granules into ITER baseline discharges. By comparing the granule induced ELM triggering size required for deuterium and non-fuel pellets on DIII-D and cross-correlating with a previously simulated JOREK calcuation of D pellet size required for ELM triggering in ITER, we estimate that a beryllium pellet of 1.5 mm diameter should provide reliable ELM triggering on ITER. This size pellet, delivered at 200 m/s should penetrate 3.5 cm past the separatrix, solidly within the H-mode steep gradient region, a location found to be advantageous for ELM triggering with minimal pellet size. Keywords: ELM pacing, granule injection, beryllium

Published
2019

43. Real time wall conditioning with lithium powder injection in long pulse H-mode plasmas in EAST with tungsten divertor

Author

Robert Lunsford, L. Wang, W. Xu, John Canik, J.S. Hu, Xianzu Gong, X. C. Meng, Alessandro Bortolon, Lingxuan Zhang, Mingguang Huang, East Team, Yaowei Yu, R. Maingi, Feng Ding, D.K. Mansfield, C. R. Wu, Guizhong Zuo, Z. Sun, and Songtao Mao

Subjects
010302 applied physics, Nuclear and High Energy Physics, Materials science, Materials Science (miscellaneous), Divertor, Evaporation, Analytical chemistry, chemistry.chemical_element, Plasma, Tungsten, lcsh:TK9001-9401, 01 natural sciences, 010305 fluids & plasmas, Nuclear Energy and Engineering, chemistry, Heat flux, Impurity, 0103 physical sciences, lcsh:Nuclear engineering. Atomic power, Lithium, Deposition (law)
Abstract

Real-time lithium powder injection has been applied to long-pulse (>30 s) H-mode plasmas in EAST. This replenishes the active lithium surface that is routinely consumed by plasma-wall interactions. The real-time injection of Li powder into long H-mode discharges effectively suppresses impurity influx and controls recycling on EAST, with an ITER-like tungsten upper divertor. With lithium powder injection, the concentrations W, Mo, and C were reduced by 50% compared to ELMy H-mode discharges. During lithium injection, two effects play a role in the suppression of impurities influx: a reduced divertor temperature and heat flux and hence reduced erosion, and impurity trapping via deposition of a Li film onto plasma-facing surfaces. The ‘fresh’ injected lithium replenishes the film deposited during daily morning evaporation, restoring the wall's pumping capability. Thus, a measurable reduction in the global recycling coefficient was observed. Keyword: Long pulse plasma, Lithium, Impurity, Recycling

Published
2019
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44. Summary of the FESAC Transformative Enabling Capabilities Panel Report

Author

C. M. Greenfield, L. Chacon, Jonathan Menard, Christopher M. Spadaccini, D.A. Humphreys, Arnold Lumsdaine, Juergen Rapp, Zhehui Wang, Anne White, R. Maingi, Brad J. Merrill, Harry McLean, Oliver Schmitz, Stephen A. Gourlay, Jean Paul Allain, Brian D. Wirth, Jerry Hughes, and Valerie Izzo

Subjects
Nuclear and High Energy Physics, Engineering, 020209 energy, Advisory committee, TEC, 02 engineering and technology, Atomic, 01 natural sciences, 010305 fluids & plasmas, Panel report, Particle and Plasma Physics, Affordable and Clean Energy, Transformative enabling capabilities, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Nuclear, General Materials Science, Civil and Structural Engineering, advanced algorithms, Energy, business.industry, Mechanical Engineering, Molecular, high critical temperature superconductors, Engineering management, Transformative learning, Nuclear Energy and Engineering, advanced materials and manufacturing, business, tritium fuel cycle control
Abstract

The U.S. Fusion Energy Sciences Advisory Committee was charged “to identify the most promising transformative enabling capabilities (TEC) for the U.S. to pursue that could promote efficient advance toward fusion energy, building on burning plasma science and technology.” A subcommittee of U.S. technical experts was formed and received community input in the form of white papers and presentations on the charge questions. The subcommittee identified four “most promising transformative enabling capabilities”: 1. advanced algorithms 2. high critical temperature superconductors 3. advanced materials and manufacturing 4. novel technologies for tritium fuel cycle control. In addition, one second-tier TEC, defined as a “promising transformative enabling capability,” was identified: fast-flowing liquid-metal plasma-facing components. Each of these TECs presents a tremendous opportunity to accelerate fusion science and technology toward power production. Dedicated investment in these TECs for fusion systems is needed to capitalize on the rapid advances being made for a variety of nonfusion applications to fully realize their transformative potential for fusion energy.

Published
2019
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45. Progress of Divertor Heat and Particle Flux Control in EAST for Advanced Steady-State Operation in the Last 10 Years

Author

Damao Yao, H. L. Du, K. Wu, G. S. Xu, X. L. Zou, Y. Duan, M. W. Chen, S. Xu, Z. P. Luo, D. Z. Wang, A. Li, Zhongshi Yang, Longxi Chen, R. Ding, Xianzu Gong, T. Y. Xia, K. F. Gan, Jin-Yong Hu, Bin Zhang, X. Y. Qian, H. Si, Baonian Wan, L. Y. Meng, Xu Jiawen, Q. Li, S. Y. Dai, David Eldon, Fang Ding, Xufeng Liu, Y. Liang, Zhen Sun, Jiefeng Wu, Guang-Nan Luo, Xudong Zhang, Guizhong Zuo, Wang Linsen, H. Q. Wang, B. Cao, Lei Zhang, J. Z. Sun, Yange Zhang, J. B. Liu, Hongbin Ding, Y. W. Yu, A.M. Garofalo, Kai Li, Y. W. Sun, R. Maingi, C. F. Sang, Xiaogang Liu, Y. P. Chen, S. C. Liu, G. Z. Deng, Houyang Guo, M. N. Jia, Q. P. Yuan, and Bingjia Xiao

Subjects
Nuclear and High Energy Physics, Materials science, Tokamak, Steady state, Nuclear engineering, Divertor, Plasma, Fusion power, 01 natural sciences, 010305 fluids & plasmas, law.invention, Nuclear Energy and Engineering, Heat flux, law, 0103 physical sciences, Particle, Nuclear fusion, 010306 general physics
Abstract

Active control of the excessively high heat and particle fluxes on the divertor target plates is of fundamental importance to the steady state operation of tokamaks, especially for fusion reactors. A series of experiments have been carried out on this critical issue to relieve the plasma-wall interactions in the experimental advanced superconducting tokamak (EAST) in the last ten years, not only contributing to the long pulse operation of EAST itself, but also providing physical understandings and potential techniques to the next-generation devices like ITER. We have characterized the power deposition pattern and broadened the divertor footprint width effectively. The plasma-wetted area is actively handled using either 3-dimentional edge magnetic topology or advanced plasma equilibrium, thereby peak heat flux around the strike point is reduced. Active control of detachment or radiation compatible with core plasma performance has progressed significantly in very recent years, with a series of active feedback control modules developed and utilized successfully, based on the divertor physics advances with both experiments and simulation. The upper divertor of EAST was upgraded from graphite to active water-cooling ITER-like tungsten in 2014, exhibiting much enhanced heat removal capability. As for the particle exhaust including both fueling and impurity particles, in addition to wall conditioning and impurity source control, the efficiency of particle flux exhaust is optimized by making full use of the divertor closure and the plasma drifts in both scrape-off layer and divertor volume. These heat and particle exhaust advances contribute greatly to a series of EAST achievements like H-mode operation over 100 s. A brief near-term plan on the integrated control of divertor plasma-wall interactions in long-time scale will also be introduced, aiming to provide favorable divertor operation solution for ITER and CFETR.

Published
2021
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46. 3D modeling of boron transport in DIII-D L-mode wall conditioning experiments

Author

Y. Feng, J. Ren, Jeremy Lore, Florian Effenberg, Tyler Abrams, Brian Grierson, A. Nagy, R. Maingi, Robert Lunsford, William R. Wampler, Todd Evans, Huiqian Wang, D. M. Orlov, Raffi Nazikian, D.L. Rudakov, Alessandro Bortolon, and Heinke Frerichs

Subjects
Nuclear and High Energy Physics, Materials science, EMC3-EIRENE, DIII-D, Materials Science (miscellaneous), chemistry.chemical_element, Impurity seeding, 01 natural sciences, Molecular physics, 010305 fluids & plasmas, Impurity flows, 0103 physical sciences, Radiative transfer, Boron, Line (formation), 010302 applied physics, Divertor, Plasma, Dissipation, lcsh:TK9001-9401, Nuclear Energy and Engineering, chemistry, Drag, Wall conditioning, lcsh:Nuclear engineering. Atomic power, Boronization
Abstract

DIII-D L-mode experiments with local boron powder injection for real-time wall conditioning have been interpreted for the first time with the 3D plasma edge transport Monte Carlo code EMC3-EIRENE. Local B sourcing in plasma scenarios with upstream densities 1 . 5 ⋅ 1 0 19 m−3 and 2.2 MW heating results in a non-axisymmetric B distribution in the scrape-off layer (SOL) and on the divertor. The SOL frictional flows at high plasma density cause a strong inboard drag of injected impurities ( ≈ 90 % ), while lower background plasma densities tend to result in a more uniform distribution. The thermal forces prevent B deposition in the near SOL while the frictional force causes B fluxes to cover the divertor plasma-facing components in a region 7–10 cm beyond the strike line. Radiative dissipation occurs for B influxes above 1 ⋅ 1 0 20 s−1 and causes a moderate, non-axisymmetric reduction of the far SOL divertor heat fluxes. A comparison of top and midplane B injection shows no substantial difference in inboard vs. outboard asymmetries of the B distribution. On the other hand, erosion or recycling at the strike line may distribute the boron more uniformly in the SOL.

Published
2021

47. Critical role of current-driven instabilities for ELMs in NSTX

Author

A. Kleiner, N.M. Ferraro, G. Canal, A. Diallo, and R. Maingi

Subjects
Nuclear and High Energy Physics, Physics::Plasma Physics, Condensed Matter Physics, OLMO
Abstract

The impact of different extended-magnetohydrodynamic (MHD) contributions on the stability thresholds of peeling-ballooning modes in ELMing and ELM-free plasmas in the spherical tokamak NSTX is investigated with the initial value code M3D-C1. We show that ELMing discharges in NSTX are limited by resistive current-driven peeling modes, whereas non-ELMing wide-pedestal H-mode discharges are located near the ideal pressure-driven ballooning threshold. It is demonstrated that extended-MHD can lead to more reliable edge stability predictions than existing ideal-MHD models. Resistive peeling-ballooning modes are found to exist well before the ideal stability threshold is met, and kink-peeling modes exhibit considerable sensitivity to plasma resistivity. Other effects not considered in ideal-MHD models affect PB modes in NSTX in a weaker way. Gyroviscous stress appears stabilizing such that the stability boundary lies closer to the experimental point. Equilibrium rotation can suppress ideal core modes and thus isolate edge modes. These results are important for the development of a predictive pedestal model for low-aspect ratio tokamaks.

Published
2022
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49. Fusion pilot plant performance and the role of a sustained high power density tokamak

Author

J.E. Menard, B.A. Grierson, T. Brown, C. Rana, Y. Zhai, F.M. Poli, R. Maingi, W. Guttenfelder, and P.B. Snyder

Subjects
Nuclear and High Energy Physics, Condensed Matter Physics
Abstract

Recent U.S. fusion development strategy reports all recommend that the U.S. should pursue innovative science and technology to enable construction of a fusion pilot plant (FPP) that produces net electricity from fusion at low capital cost. Compact tokamaks have been proposed as a means of potentially reducing the capital cost of a FPP. However, compact steady-state tokamak FPPs face the challenge of integrating a high fraction of self-driven current with high core confinement, plasma pressure, and high divertor parallel heat flux. This integration is sufficiently challenging that a dedicated sustained-high-power-density (SHPD) tokamak facility is proposed by the U.S. community as the optimal way to close this integration gap. Performance projections for the steady-state tokamak FPP regime are presented and a preliminary SHPD device with substantial flexibility in lower aspect ratio (A = 2–2.5), shaping, and divertor configuration to narrow gaps to an FPP is described.

Published
2022
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