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An International Thermonuclear Experimental Reactor (ITER) plasma position reflectometry (PPR) diagnostic system is designed to analyze the plasma edge electron density profile at four representative positions that are strategically distributed throughout the vacuum vessel. Every transmission line (TL) in the PPR is routed from the corresponding port-plug, through the port-cell and gallery, to the Diagnostic Area or Assembly Hall Building. Ex-vessel TLs are made up of oversized circular corrugated waveguides (WGs), which are positioned by adjustable supports. These WG supports are of utmost importance, not only to avoid inducing stresses on the TL in the assembly process, but also to ensure the performance of the PPR system. The current work is focused on the structural analyses of the WG supports when bearing the mechanical loads calculated in a previous global analysis of the entire PPR system. The finite element analysis (FEA) model of the WG support includes the bolt and nut assemblies, so that appropriate selection of their preload can be evaluated. The main objective of the analysis is to assess the structural integrity of the WG support according to the design and construction rules for mechanical components of nuclear installations (RCC-MR) code. WG support deformations are also calculated for load cases in Categories I and II, to assure that the PPR system maintains the service function with the required performance.

TJ-II stellarator results on modelling and validation of plasma flow asymmetries due to on-surface potential variations, plasma fuelling physics, Alfvén eigenmodes (AEs) control and stability, the interplay between turbulence and neoclassical (NC) mechanisms and liquid metals are reported. Regarding the validation of the neoclassically predicted potential asymmetries, its impact on the radial electric field along the flux surface has been successfully validated against Doppler reflectometry measurements. Research on the physics and modelling of plasma core fuelling with pellets and tracer encapsulated solid pellet injection has shown that, although post-injection particle radial redistributions can be understood qualitatively from NC mechanisms, turbulence and fluctuations are strongly affected during the ablation process. Advanced analysis tools based on transfer entropy have shown that radial electric fields do not only affect the radial turbulence correlation length but are also capable of reducing the propagation of turbulence from the edge into the scrape-off layer. Direct experimental observation of long range correlated structures show that zonal flow structures are ubiquitous in the whole plasma cross-section in the TJ-II stellarator. Alfvénic activity control strategies using ECRH and ECCD as well as the relation between zonal structures and AEs are reported. Finally, the behaviour of liquid metals exposed to hot and cold plasmas in a capillary porous system container was investigated.

We present recent highlights from the most recent operation phases of Wendelstein 7-X, the most advanced stellarator in the world. Stable detachment with good particle exhaust, low impurity content, and energy confinement times exceeding 100 ms, have been maintained for tens of seconds. Pellet fueling allows for plasma phases with reduced ion-temperature-gradient turbulence, and during such phases, the overall confinement is so good (energy confinement times often exceeding 200 ms) that the attained density and temperature profiles would not have been possible in less optimized devices, since they would have had neoclassical transport losses exceeding the heating applied in W7-X. This provides proof that the reduction of neoclassical transport through magnetic field optimization is successful. W7-X plasmas generally show good impurity screening and high plasma purity, but there is evidence of longer impurity confinement times during turbulence-suppressed phases. 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. Peer Reviewed Article signat per 497 autors/es: Thomas Sunn Pedersen1,2,∗ , I. Abramovic3, P. Agostinetti4, M. Agredano Torres1, S. Äkäslompolo1, J. Alcuson Belloso1, P. Aleynikov1, K. Aleynikova1, M. Alhashimi1, A. Ali1, N. Allen5, A. Alonso6, G. Anda7, T. Andreeva1, C. Angioni8, A. Arkhipov8, A. Arnold1, W. Asad8, E. Ascasibar6, M.-H. Aumeunier9, K. Avramidis10, E. Aymerich11, S.-G. Baek3, J. Bähner1, A. Baillod12, M. Balden1, M. Balden8, J. Baldzuhn1, S. Ballinger3, M. Banduch1, S. Bannmann1, A. Banon Navarro8, A. Bañon Navarro ´ 1, T. Barbui13, C. Beidler1, C. Belafdil9, A. Bencze7, A. Benndorf1, M. Beurskens1, C. Biedermann1, O. Biletskyi14, B. Blackwell15, M. Blatzheim1, T. Bluhm1, D. Böckenhoff1, G. Bongiovi16, M. Borchardt1, D. Borodin17, J. Boscary8, H. Bosch1,18, T. Bosmann19, B. Böswirth8, L. Böttger1, A. Bottino8, S. Bozhenkov1, R. Brakel1, C. Brandt1, T. Bräuer1, H. Braune1, S. Brezinsek17, K. Brunner1, S. Buller1, R. Burhenn1, R. Bussiahn1, B. Buttenschön1, A. Buzás7, V. Bykov1, I. Calvo6, K. Camacho Mata1, I. Caminal20, B. Cannas11, A. Cappa6, A. Carls1, F. Carovani1, M. Carr21, D. Carralero6, B. Carvalho22, J. Casas20, D. Castano-Bardawil17, F. Castejon6, N. Chaudhary1, I. Chelis23, A. Chomiczewska24, J.W. Coenen13,17, M. Cole1, F. Cordella25, Y. Corre9, K. Crombe26, G. Cseh7, B. Csillag7, H. Damm1, C. Day10, M. de Baar27, E. De la Cal6, S. Degenkolbe1, A. Demby13, S. Denk3, C. Dhard1, A. Di Siena8,28, A. Dinklage12, T. Dittmar17, M. Dreval14, M. Drevlak1, P. Drewelow1, P. Drews17, D. Dunai7, E. Edlund3, F. Effenberg29, G. Ehrke1, M. Endler1, D.A. Ennis5, F.J. Escoto6, T. Estrada6, E. Fable8, N. Fahrenkamp1, A. Fanni11, J. Faustin1, J. Fellinger1, Y. Feng1, W. Figacz4, E. Flom13, O. Ford1, T. Fornal24, H. Frerichs13, S. Freundt1, G. Fuchert1, M. Fukuyama30, F. Füllenbach1, G. Gantenbein10, Y. Gao1, K. Garcia13, J.M. García Regaña6, I. García-Cortés6, J. Gaspar31, D.A. Gates29, J. Geiger1, B. Geiger13, L. Giudicotti32, A. González6, A. Goriaev26,33, D. Gradic1, M. Grahl1, J.P. Graves12, J. Green13, E. Grelier9, H. Greuner8, S. Groß1, H. Grote1, M. Groth34, M. Gruca24, O. Grulke1,35, M. Grün1, J. Guerrero Arnaiz1, S. Günter8, V. Haak1, M. Haas1, P. Hacker1, A. Hakola36, A. Hallenbert1, K. Hammond29, X. Han17,37, S.K. Hansen3, J.H. Harris38, H. Hartfuß1, D. Hartmann1, D. Hathiramani1, R. Hatzky8, J. Hawke39, S. Hegedus7, B. Hein8, B. Heinemann8, P. Helander12, S. Henneberg1, U. Hergenhahn8,40, C. Hidalgo6, F. Hindenlang8, M. Hirsch1, U. Höfel1, K.P. Hollfeld17, A. Holtz1, D. Hopf8, D. Höschen17, M. Houry9, J. Howard19, X. Huang41, M. Hubeny17, S. Hudson29, K. Ida9, Y. Igitkhanov10, V. Igochine8, S. Illy10, C. Ionita-Schrittwieser42, M. Isobe39, M. Jabłczynska ´ 24, S. Jablonski24, B. Jagielski1, M. Jakubowski1, A. Jansen van Vuuren1, J. Jelonnek10, F. Jenko8, F. Jenko8, T. Jensen35, H. Jenzsch1, P. Junghanns8, J. Kaczmarczyk24, J. Kallmeyer1, U. Kamionka1, M. Kandler8, S. Kasilov43, Y. Kazakov26, D. Kennedy1, A. Kharwandikar1, M. Khokhlov1, C. Kiefer8, C. Killer1, A. Kirschner17, R. Kleiber1, T. Klinger12, S. Klose1, J. Knauer1, A. Knieps17, F. Köchl44, G. Kocsis7, Ya.I. Kolesnichenko45, A. Könies1, R. König1, J. Kontula34, P. Kornejew1, J. Koschinsky, M.M. Kozulia14, A. Krämer-Flecken17, R. Krampitz1, M. Krause1, N. Krawczyk24, T. Kremeyer1, L. Krier10, D.M. Kriete5, M. Krychowiak1, I. Ksiazek46, M. Kubkowska24, M. Kuczynski1, G. Kühner1, A. Kumar15, T. Kurki-Suonio34, S. Kwak1, M. Landreman47, P.T. Lang8, A. Langenberg1, H.P. Laqua12, H. Laqua1, R. Laube1, S. Lazerson1, M. Lewerentz1, C. Li17, Y. Liang17, Ch. Linsmeier17, J. Lion1, A. Litnovsky17,48, S. Liu37, J. Lobsien1, J. Loizu12, J. Lore38, A. Lorenz1, U. Losada6, F. Louche26, R. Lunsford29, V. Lutsenko45, M. Machielsen12, F. Mackel8, J. Maisano-Brown3, O. Maj8, D. Makowski49, G. Manduchi50, E. Maragkoudakis6, O. Marchuk17, S. Marsen1, E. Martines4, J. Martinez-Fernandez6, M. Marushchenko1, S. Masuzaki41, D. Maurer5, M. Mayer8, K.J. McCarthy6, O. Mccormack4, P. McNeely1, H. Meister8, B. Mendelevitch8, S. Mendes1, A. Merlo1, A. Messian26, A. Mielczarek49, O. Mishchenko1, B. Missal1, R. Mitteau9, V.E. Moiseenko14, A. Mollen1, V. Moncada9, T. Mönnich1, T. Morisaki41, D. Moseev1, G. Motojima41, S. Mulas6, M. Mulsow1, M. Nagel1, D. Naujoks1, V. Naulin35, T. Neelis19, H. Neilson29, R. Neu8, O. Neubauer17, U. Neuner1, D. Nicolai17, S.K. Nielsen35, H. Niemann1, T. Nishiza1, T. Nishizawa1, T. Nishizawa8, C. Nührenberg1, R. Ochoukov8, J. Oelmann17, G. Offermanns17 K. Ogawa41, S. Okamura41, J. Ölmanns17, J. Ongena26, J. Oosterbeek1, M. Otte1, N. Pablant29, N. Panadero Alvarez6, N. Panadero Alvarez6, A. Pandey1, E. Pasch1, R. Pavlichenko14, A. Pavone1, E. Pawelec46, G. Pechstein1, G. Pelka24, V. Perseo1, B. Peterson41, D. Pilopp1, S. Pingel1, F. Pisano11, B. Plöckl8, G. Plunk1, P. Pölöskei1, B. Pompe2, A. Popov51, M. Porkolab3, J. Proll19, M.J. Pueschel19,27, M.-E. Puiatti52, A. Puig Sitjes1, F. Purps1, K. Rahbarnia1, M. Rasinski ´ 17, J. Rasmussen35, A. Reiman29, F. Reimold1, M. Reisner8, D. Reiter17, M. Richou9, R. Riedl8, J. Riemann1, K. Riße1, G. Roberg-Clark1, V. Rohde8, J. Romazanov17, D. Rondeshagen1, P. Rong1, L. Rudischhauser1, T. Rummel1, K. Rummel1, A. Runov1, N. Rust1, L. Ryc24, P. Salembier20, M. Salewski35, E. Sanchez6, S. Satake41, G. Satheeswaran17, J. Schacht1, E. Scharff1, F. Schauer8, J. Schilling1, G. Schlisio1, K. Schmid8, J. Schmitt5, O. Schmitz13, W. Schneider1, M. Schneider1, P. Schneider8, R. Schrittwieser42, T. Schröder1, M. Schröder1, R. Schroeder1, B. Schweer26, D. Schwörer1, E. Scott1, E. Scott8, B. Shanahan1, G. Sias11, P. Sichta29, M. Singer1, P. Sinha29, S. Sipliä34, C. Slaby1, M. Sleczka53, H. Smith1, J. Smoniewski54, E. Sonnendrücker8, M. Spolaore4, A. Spring1, R. Stadler8, D. Stanczak24, T. Stange1, I. Stepanov26, L. Stephey13, J. Stober8, U. Stroth8,55, E. Strumberger8, C. Suzuki41, Y. Suzuki41, J. Svensson1, T. Szabolics7, T. Szepesi7, M. Szücs7, F.L. Tabares6, N. Tamura41, A. Tancetti35, C. Tantos10, J. Terry3, H. Thienpondt6, H. Thomsen1, M. Thumm10, J.M. Travere9, P. Traverso5, J. Tretter8, E. Trier8, H. Trimino Mora1, T. Tsujimura41, Y. Turkin1, A. Tykhyi45, B. Unterberg17, P. van Eeten1, B.Ph. van Milligen6, M. van Schoor26, L. Vano1, S. Varoutis10, M. Vecsei7, L. Vela56, J.L. Velasco6, M. Vervier17, N. Vianello50, H. Viebke1, R. Vilbrandt1, G. Vogel8, N. Vogt1, C. Volkhausen1, A. von Stechow1, F. Wagner1, E. Wang17, H. Wang57, F. Warmer1, T. Wauters26, L. Wegener1, T. Wegner1, G. Weir1, U. Wenzel1, A. White3, F. Wilde1, F. Wilms1, T. Windisch1, M. Winkler1, A. Winter1, V. Winters1, R. Wolf118, A.M. Wright29, G.A. Wurden39, P. Xanthopoulos1, S. Xu17, H. Yamada58, H. Yamaguchi41, M. Yokoyama41, M. Yoshinuma41, Q. Yu8, M. Zamanov14, M. Zanini1, M. Zarnstorff29, D. Zhang1, S. Zhou17, J. Zhu1, C. Zhu29, M. Zilker8, A. Zocco1, H. Zohm8, S. Zoletnik7 and L. Zsuga7 // 1 Max Planck Institute for Plasma Physics, Garching and Greifswald, Germany: 2 University of Greifswald, Greifswald, Germany; 3 Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, United States of America; 4 Consorzio RFX, Corso Stati Uniti, 4-35127 Padova, Italy; 5 Auburn University, Auburn, AL 36849, United States of America; 6 CIEMAT, Avenida Complutense, 40, 28040 Madrid, Spain; 7 Center for Energy Research, Konkoly-Thegeut 29-33, 1121 Budapest, Hungary; 8 Max-Planck-Institute for Plasma Physics, Boltzmannstraße 2, 85748 Garching bei München, Germany; 9 CEA Cadarache, 13115 Saint-Paul-lez-Durance, France; 10 Karlsruhe Institute of Technology, Kaiserstr. 12, 76131 Karlsruhe, Germany; 11 University of Cagliari, Via Universita, 40, 09124 Cagliari, Italy; 12 École Polytechnique Fédérale de Lausanne, Swiss Plasma Center, CH-1015 Lausanne, Switzerland; 13 University of Wisconsin–Madison, Engineering Drive, Madison, WI 53706, United States of America; 14 Institute of Plasma Physics, National Science Center ‘Kharkiv Institute of Physics and Technology’, Kharkiv, Ukraine; 15 The Australian National University, Acton ACT 2601, Canberra, Australia; 16 Department of Engineering, University of Palermo, Viale delle Scienze, Edificio 6, Palermo, 90128, Italy; 17 Forschungszentrum Jülich GmbH, Institut für Energie-und Klimaforschung—Plasmaphysik, 52425 Jülich, Germany; 18 Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany; 19 Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands; 20 Universitat Politècnica de Catalunya. BarcelonaTech, C. Jordi Girona, 31, 08034 Barcelona, Spain; 21 Culham Center for Fusion Energy, Abingdon OX14 3EB, United Kingdom; 22 Instituto de Plasmas e Fusao Nuclear, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; 23 Department of Physics, National and Kapodistrian University of Athens, 15784 Athens, Greece; 24 Institute of Plasma Physics and Laser Microfusion, 23 Hery Str., 01-497 Warsaw, Poland; 25 ENEA—Centro Ricerche Frascati, Via Enrico Fermi, 45, 00044 Frascati RM, Italy; 26 Laboratory for Plasma Physics, LPP-ERM/KMS, TEC Partner, B-1000 Brussels, Belgium; 27 Dutch Institute for Fundamental Energy Research, PO Box 6336, 5600 HH Eindhoven, Netherlands; 28 University of Texas, Austin, TX, United States of America; 29 Princeton Plasma Physics Laboratory, Princeton, NJ 08543, United States of America; 30 Kyushu University, 744 Motooka Nishi-ku, Fukuoka 819-0395, Japan; 31 Aix-Marseille University, Jardin du Pharo, 58 Boulevard Charles Livon, 13007, Marseille, France; 32 Department of Physics and Astronomy, Padova University, Via Marzolo 8, 35131 Padova, Italy; 33 Department of Applied Physics, Ghent University, Sint-Pietersnieuwstraat 41 B4, 9000 Ghent, Belgium; 34 Aalto University, 02150 Espoo, Finland; 35 Department of Physics, Technical University of Denmark, Anker Engelunds Vej, 2800 Kgs Lyngby, Denmark; 36 VTT Technical Research Center of Finland Ltd., PO Box 1000, FI-02044 VTT, Finland; 37 Institute of Plasma Physics, Chinese Academy of Sciences, 230031 Hefei, Anhui, China; 38 Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37830, United States of America; 39 Los Alamos National Laboratory, NM 87545, United States of America; 40 Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany; 41 National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho, Toki, Gifu Prefecture 509-5292, Japan; 42 Institute for Ion Physics and Applied Physics, University of Innsbruck, Innsbruck, Austria; 43 Graz University of Technology, Rechbauerstraße 12, 8010 GRAZ, Austria; 44 Austrian Academy of Science, Doktor-Ignaz-Seipel-Platz 2, 1010 Wien, Austria; 45 Institute for Nuclear Research, prospekt Nauky 47, Kyiv 03028, Ukraine; 46 University of Opole, plac Kopernika 11a, 45-001 Opole, Poland; 47 University of Maryland, Paint Branch Drive, College Park, MA 20742, United States of America; 48 National Research Nuclear University MEPhI, 115409 Moscow, Russian Federation; 49 Department of Microelectronics and Computer Science, Lodz University of Technology, Wolczanska 221/223, 90-924 Lodz, Poland; 50 Consiglio Nazionale delle Ricerche, Piazzale Aldo Moro, 7, 00185 Roma, Italy; 51 Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 26 Politekhnicheskaya, St Petersburg 194021, Russian Federation; 52 Istituto di Fisica del Plasma Piero Caldirola, Via Roberto Cozzi, 53, 20125 Milano, Italy; 53 University of Szczecin, 70-453, aleja Papieza Jana Pawła II 22A, Szczecin, Poland; 54 Lawrence University, 711 E Boldt Way, Appleton, WI 54911, United States of America; 55 Physik-Department E28, Technische Universität München, 85747 Garching, Germany; 56 Universidad Carlos III de Madrid, Av. de la Universidad, 30 Madrid, Spain; 57 Yale University, New Haven, CT 06520, United States of America; 58 University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chhiab 277-0882, Japan Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.a - Per a 2030, augmentar la cooperació internacional per tal de facilitar l’accés a la investigació i a les tecnolo­gies energètiques no contaminants, incloses les fonts d’energia renovables, l’eficiència energètica i les tecnologies de combustibles fòssils avançades i menys contaminants, i promoure la inversió en infraestructures energètiques i tecnologies d’energia no contaminant

Design parameters of the ITER Plasma Position Reflectometer (PPR) in-port-plug antennas are determined and their measurement performance is assessed using 2D full wave analysis. Two ITER scenarios were selected in order to determine the optimum antenna position and orientation, namely the ITER QDT = 10 baseline scenario (15 MA) and the low density one planned for the initial non-active phase at 7.5 MA. Using them to feed a 3D ray tracing code, the spatial position and optimum orientation angles of each set of emission and detection antennas were determined. Additionally, a far field analysis of the launching radiation patterns led to the definition of the antenna dimensions in terms of optimal power coupling. After this preliminary work, 2D full wave simulations using a finite difference time domain (FDTD) code were carried out to assess the measurement performance of the system. To this end, the detected wave amplitudes and phases were evaluated for each scenario and two models of the scrape-off layer (SOL) density profiles. By calculating the spectrogram of the complex amplitude of the detected wave, the reconstruction of the plasma density profile can be made and be directly compared with the input profiles. As a result from this synthetic diagnostic analysis, an estimation of the error in the determination of the last closed flux surface position was possible.

The Plasma Position Reflectometry (PPR) diagnostic system is planned to provide information related to the edge electron density profile and plasma position at four defined locations distributed both poloidally and toroidally in the ITER vacuum vessel. It consists of five fully independent reflectometers grouped in three different paths, depending on the port through which are routed (Equatorial Port 10, Upper Port 01 and Upper Port 14), with different lengths and waveguide number and distribution. The sections of the ex-vessel transmission lines (TL) in the Gallery, between the two secondary confinement barriers, are considered “captive components”. They are installed as close as possible to the ceiling and are trapped by other systems installed below so they will not be accessible for repair. This paper summarizes the design, the analysis strategy and main results of global analyses for each PPR route in the Gallery in order to analyze global deformations, reactions on supports and identify the critical parts of the whole PPR system. Based on the results obtained in the global model, detailed models will be built in future studies for critical components to assess their structural integrity.

The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor radius , and plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of with central electron temperatures were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of a temperature of with was transiently accomplished, which corresponds to with a peak diamagnetic energy of and volume-averaged normalized plasma pressure . The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above line integrated density and central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.

A recent characterization of core turbulence carried out with a Doppler reflectometer in the optimized stellarator Wendelstein 7-X (W7-X) found that discharges achieving high ion temperatures at the core featured an ITG-like suppression of density fluctuations driven by a reduction of the gradient ratio $\eta_i = L_n/L_{T_i}$ [D. Carralero et al., Nucl. Fusion, 2021]. In order to confirm the role of ITG turbulence in this process, we set out to establish experimentally the relation between core density fluctuations, turbulent heat flux and global confinement. With this aim, we consider the scenarios found in the previous work and carry out power balance analysis for a number of representative ones, including some featuring high ion temperature. As well, we evaluate the global energy confinement time and discuss it in the context of the ISS04 inter-stellarator scaling. We find that, when turbulence is suppressed as a result of a reduction of $\eta_i$, there is a reduction of ion turbulent transport, and global performance is improved as a result. This is consistent with ITG turbulence limiting the ion temperature at the core of W7-X. In contrast, when turbulence is reduced following a decrease in collisionality, no changes are observed in transport or confinement. This could be explained by ITG modes being combined with TEM turbulence when the later is destabilized at low collisionalities., Comment: Submitted to PPCF, 47th EPS special issue

In this work we present a study on the viability and practicality of installing a Doppler reflectometer (DR) system in the JT-60SA advanced tokamak. First, we discuss its scientific scope in the context of the JT-60SA research plan. We identify a number of fields in which a DR would be very relevant for the accomplishment of said plan and outline a scientific program for the diagnostic. Then, starting from a number of design hypothesis, we use a ray tracing code to carry out a feasibility study for a number of relevant scenarios and identify a geometric solution for the installation of a DR such that both core and edge can be probed in the prescribed wave number range, thus achieving the proposed scientific objectives. Finally, we perform a preliminary discussion on the different possibilities for a conceptual design (including a minimum viable system and a baseline system) and their requirements in terms of components and space. We conclude that a viable conceptual design could be carried out using a small fraction of a horizontal port, leaving room for additional diagnostic systems.

Observations on confinement in the first experimental campaign on the optimized Stellarator Wendelstein 7-X are summarized. In this phase W7-X was equipped with five inboard limiters only and thus the discharge length restricted to avoid local overheating. Stationary plasmas are limited to low densities

There is great need for veterinary care for working equids worldwide. Addressing this need provides an opportunity for veterinary students to gain primary care experience. An annual two week collaborative outreach and educational program with Michigan State University (MSU), the Universidad Nacional Aut&oacute, noma de M&eacute, xico (UNAM) and the Universidad Veracruzana (UV) was developed to provide care for working equids in rural Mexican communities. From 2017 to 2019 24 US veterinary students and 25 Mexican veterinary students, interns and residents examined, vaccinated and dewormed more than 2200 equids and performed more than 80 castrations, 100 rectal palpations for pregnancy diagnosis, 220 dental floats and 320 hoof trims. They also treated many wounds, sarcoids, vampire bat bites and tick infestations and also saw unusual cases including tetanus, eye injuries, nuchal bursitis, cervical vertebral malformation and suspected vesicular stomatitis. Development of the collaborative MSU-UNAM-UV Equine Welfare in Practice Clerkship required vision, learning, relationship building, creativity, fund-raising and perseverance to develop and agree on mutually beneficial objectives for all participants. The project is largely financed through private donations and supplies provided by pharmaceutical companies. The outcome has been a highly successful program that could be used as a model by other Colleges of Veterinary Medicine world-wide.

The mean tilt angle of turbulent structures is a key element for describing the turbulence and its interplay with plasma flows in magnetically confined plasmas. It is a quantity predicted by theories and gyrokinetic simulations, which can provide information on the type of the dominant micro-instability, and also on the turbulence anisotropy induced by sheared flows. A new method for measuring the tilt angle of turbulent structures using Doppler reflectometry has been recently introduced (Pinzón et al 2019 Nucl. Fusion 59 074002). It is based on the time delay of the cross-correlation between microwaves backscattered at radially displaced positions. In this paper, the method is presented in detail and is successfully applied on the ASDEX Upgrade tokamak and the TJ-II stellarator. Measurements of the tilt angle in the core of both machines are reported, in the TJ-II case, for the first time.

2D poloidal contour plots of plasma potential, plasma density, and their fluctuations have been measured in low density plasmas sustained by Electron Cyclotron Resonance Heating using a heavy ion beam probe (HIBP) system in the TJ-II stellarator. A HIBP has been used in the new energy scanning mode to obtain the measurements for a 2D poloidal cross section of the stellarator. The 2D map for the absolute plasma potential shows a local maximum in the plasma core as expected in low density plasma scenarios. Fluctuations in the HIBP secondary ion current, as a proxy of plasma density fluctuations, appear both in positive and negative density gradient regions, with a normalized level of density fluctuations higher in the negative density gradient region. The TJ-II innovative experimental setup developed using a dual HIBP diagnostic paves the way for model validation on core plasma potential asymmetries and particle transport and fluctuations under positive and negative density gradient scenarios.

This work describes the microwave design of the transmission line housed in the inport- plug region of the ITER plasma position reflectometer (PPR). The design of the components of the in-port-plug reflectometers (located in equatorial port-plug 10 (EPP10) and in upper-portplug 01 (UPP01)) is presented. Using a 3D ray tracing code, the spatial position and optimum orientation angles of each set of emission and detection antennas were determined. A feasible path was then created from the obtained antenna positions and orientations to the primary vaccum window. Oversized tall waveguides were chosen in order to reduce ohmic losses. Due to space constraints in the ITER crowded environment, bends in oversized waveguides were unavoidable and thus mode conversion was produced. In order to keep mode conversion losses at bay, hyperbolic secant curvature bends had to be used whenever possible. However, E-plane bends in tall waveguides proved to be especially critical, making it necessary to employ other approaches when higher bending angles were needed. Mode conversion results were obtained by evaluating the mode coupling equations. Ohmic losses have been also computed and their results compared with commercial simulators, obtaining a perfect agreement.

In the present work we report recent radial electric field measurements carried out with the Doppler reflectometry system in the TJ-II stellarator. The study focuses on the fact that, under some conditions, the radial electric field measured at different points over the same flux surface shows significantly different values. A numerical analysis is carried out considering the contribution arising from the radial dependence of $\Phi_1$ as a possible correction term to the total radial electric field. Here $\Phi_1$ is the neoclassical electrostatic potential variation over the surface. The comparison shows good agreement in some aspects, like the conditions under which this correction is large (electron-root conditions) or negligible (ion-root conditions). But it disagrees in others like the sign of the correction. The results are discussed together with the underlying reasons of this partial disagreement. In addition, motivated by the recent installation of the dual Doppler reflectometry system in Wendelstein 7-X (W7-X), $\Phi_1$ estimations for W7-X are revisited considering Core-Electron-Root-Plasma (CERC) plasmas from its first experimental campaign. The simulations show larger values of $\Phi_1$ under electron-root conditions than under ion root ones. The contribution from the kinetic electron response is shown to become important at some radii. All this results in a potential variation size noticeably larger than estimated in our previous work in W7-X \cite{Regana_nf_57_056004_2017} for other plasma parameters and another configuration., Comment: 23 pages, 10 figures

The effects of 3D geometry are explored in TJ-II from two relevant points of view: neoclassical transport and modification of stability and dispersion relation of waves. Particle fuelling and impurity transport are studied considering the 3D transport properties, paying attention to both neoclassical transport and other possible mechanisms. The effects of the 3D magnetic topology on stability, confinement and Alfvén Eigenmodes properties are also explored, showing the possibility of controlling Alfvén modes by modifying the configuration; the onset of modes similar to geodesic acoustic modes are driven by fast electrons or fast ions; and the weak effect of magnetic well on confinement. Finally, we show innovative power exhaust scenarios using liquid metals.

Dedicated experiments have been carried out for a systematic comparison of turbulence wavenumber spectra and perpendicular rotation velocity measured at poloidally separated positions on the same flux-surface in the stellarator TJ-II. The rationale behind this study is twofold, namely, validation of the spatial localization of instabilities predicted by gyrokinetic simulations in stellarators and validation of the electrostatic potential variation on the flux surface as calculated by neoclassical codes and its possible impact on the radial electric field. Perpendicular wavenumber spectra and perpendicular rotation velocity profiles have been measured using Doppler reflectometry in two plasma regions poloidally separated as both positive and negative probing beam angles with respect to normal incidence can be selected. A systematic comparison has been carried out showing differences in the perpendicular wavenumber spectrum measured at poloidally separated positions on the same flux-surface, that depend on plasma density, heating conditions and magnetic configuration. The asymmetry found in the standard magnetic configuration under some plasmas conditions, reverses in the high iota configuration. The different intensity in the density fluctuation spectra can be related to the poloidal localization of instabilities found in gyrokinetic simulations. Differences in the radial electric field profile are also found that could be explained to be due to on-surface plasma potential variations.

In this letter, we investigate the spatial structure of a low frequency global potential oscillation, which is likely ascribed as the low frequency zonal flows, in TJ-II laboratory plasmas. In two plasmas produced by different heating schemes (electron cyclotron resonance heating and neutral beam injection heating) and characterized by different mean radial electric field structures, frequency-space-decomposed spectra of the global potential oscillation are obtained. In both cases, the oscillatory field has a single-peaked potential structure and a dipole radial electric field structure. The oscillating structure depends on its frequency as well as on the heating scheme.

Wendelstein 7-X, a superconducting optimized stellarator built in Greifswald/Germany, started its first plasmas with the last closed flux surface (LCFS) defined by 5 uncooled graphite limiters in December 2015. At the end of the 10 weeks long experimental campaign (OP1.1) more than 20 independent diagnostic systems were in operation, allowing detailed studies of many interesting plasma phenomena. For example, fast neutral gas manometers supported by video cameras (including one fast-frame camera with frame rates of tens of kHz) as well as visible cameras with different interference filters, with field of views covering all ten half-modules of the stellarator, discovered a MARFE-like radiation zone on the inboard side of machine module 4. This structure is presumably triggered by an inadvertent plasma-wall interaction in module 4 resulting in a high impurity influx that terminates some discharges by radiation cooling. The main plasma parameters achieved in OP1.1 exceeded predicted values in discharges of a length reaching 6 s. Although OP1.1 is characterized by short pulses, many of the diagnostics are already designed for quasi-steady state operation of 30 min discharges heated at 10 MW of ECRH. An overview of diagnostic performance for OP1.1 is given, including some highlights from the physics campaigns.

Measurements of the relaxation of a zonal electrostatic potential perturbation in a non-axisymmetric magnetically confined plasma are presented. A sudden perturbation of the plasma equilibrium is induced by the injection of a cryogenic hydrogen pellet in the TJ-II stellarator, which is observed to be followed by a damped oscillation in the electrostatic potential. The waveform of the relaxation is consistent with theoretical calculations of zonal potential relaxation in a non-axisymmetric magnetic geometry. The turbulent transport properties of a magnetic confinement configuration are expected to depend on the features of the collisionless damping of zonal flows, of which the present letter is the first direct observation.

This work explores the relation between magnetic islands, long range temporal correlations and heat transport. A low order rational surface ($\iota/2\pi = 3/2$) was purposely scanned outward through an Electron Cyclotron Resonance Heated (ECRH) plasma in the TJ-II stellarator. Density turbulence and the poloidal flow velocity (or radial electric field) were characterized using a two channel Doppler Reflectometer. Simultaneously, the ECRH power was modulated to characterize heat transport, using measurements from a 12 channel Electron Cyclotron Emission diagnostic. A systematic variation of the poloidal velocity was found to be associated with the stationary $\iota/2\pi = 3/2$ magnetic island. Inside from the rational surface, the Hurst coefficient, quantifying the nature of long-range correlations, was found to be significantly enhanced. Simultaneously, heat transport was enhanced as well, establishing a clear link between density fluctuations and anomalous heat transport. The variation of the Hurst coefficient was consistent with a magnetohydrodynamic turbulence simulation., Comment: 38 pages, 18 figures

Band-stop or notch filters play a crucial role in plasma diagnosis systems to protect receivers from the stray radiation. In this work, a rigorous design process based on circuit synthesis in addition to an extremely compact E-plane waveguide structure is proposed for this kind of filters. On the one hand, the transfer function verifying the rejection specification is analytically obtained, fixing the minimum number of required cavities. On the other hand, a coupling structure that reduces drastically the unwanted resonances in filters with a very large pass band requirement, is presented. This coupling between the rejection cavities and the main rectangular waveguide has additional advantages; (a) unlike typical inductive irises, large coupling coefficients can be implemented (b) a pure E-plane configuration is achieved, which simplifies the manufacturing and also reduces significantly the computational effort. Experimental validation is demonstrated by two pseudo-elliptic fifth-order band-stop filters fabricated and measured in Ka and V bands. In both cases, the filters are free of spurious resonances in their total operation bands.

The charge state distributions of randomly sulfated cyclodextrins from Sigma-Aldrich and Beckman-Coulter, as well as single isomer sulfated cyclodextrins from TM Chemicals LP were investigated using hydrophilic interaction liquid chromatography (HILIC). A cross-linked diol phase and an unbonded silica phase were used as HILIC stationary phases. Groups of sulfated cyclodextrins with different charge states were resolved from each other, while regioisomers in a charge group were partially separated. A ladder of sulfated cyclodextrins having a charge state distribution from 1 to 14 was prepared and was used to determine the charge state heterogeneity of the commercially available sulfated cyclodextrin samples. Wide charge state and regioisomer distributions are seen for the randomly sulfated cyclodextrins, while HILIC analysis of every single isomer sulfated cyclodextrin sample indicates the presence of a single species.

This paper is an extension of global plasma confinement in electron-cyclotron operation to neutral beam heated plasmas in TJ-II. The reported NBI plasmas have been obtained under lithium-coated wall conditions. The plasma operation exhibits a substantially better density control and improved confinement as compared to similar boron-coated wall discharges heated by NBI. Regression analyses of energy confinement time yield a scaling law indicating degradation with power with an exponent of αP = 0.8. The scaling shows an improvement with density with exponent αn = 0.5. The dependencies on plasma radius and rotational transform have not been resolved so far because the –still incomplete– NBI database suffers from a high correlation between these two parameters (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Dynamic magnetic configuration scan experiments have been conducted in order to investigate the influence of the rotational transform on plasma rotation, radial electric field and turbulence. The main magnetic resonances (7/4 and 5/3 in this work) make a positive contribution to the local radial electric field, which depends on the plasma density and plasma radius. A local reduction in the level of density fluctuations due to the influence of low order rational surfaces is also observed. These results could explain local transport changes associated to low order rational surfaces observed in TJ-II ECH plasmas (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper describes the purpose and the structure of the database of confinement improvement modes in helical devices under activities of the International Stellarator/Heliotron Profile Database (ISHPDB). Data are being collected from 4 devices: CHS, LHD, TJ-II and W7-AS. This database will include sets of profiles and global data prior to a transition and ones in the fully developed improved mode in the UFILE format, detailed edge profiles and thresholds of the power and the density for the transition (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In the TJ-II stellarator, L- to H-mode transitions are achieved under NBI heating conditions when operating with lithium coated walls. Several magnetic configurations have been explored in order to study the influence of the rotational transform in the transition. The shear of the negative radial electric field, Er, increases at the L-H transition by an amount that depends on the magnetic configuration and heating power. Magnetic configurations with and without a low order rational surface close to the plasma edge show differences that may be interpreted in terms of local changes in the radial electric field induced by the rational surface that could facilitate the L-H transition. Fluctuation measurements show a reduction in the turbulence level that is strongest at the position of maximum Er shear. High temporal and spatial resolution measurements indicate that turbulence reduction precedes the increase in the mean sheared flow, but is simultaneous with the increase in the low frequency oscillating sheared flow. These observations may be interpreted in terms of turbulence suppression by oscillating flows, the so-called zonal flows (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The Spanish stellarator TJ-II has been operated under lithium wall conditions for two years so far. Important changes in plasma parameters and, in particular, on particle recycling have been recorded with respect to the normal, boronized wall conditions previously prevailing. The specific effects that the new recycling scenario could have on the improved plasma parameters, and in particular to the global energy balance of electrons and protons are addressed in the present work. In addition, the possible increase in ion energies impinging on the walls should be mirrored by the incoming flux of sputtered lithium atoms. However, a strong decrease of the corresponding sputtering yield is recorded. This effect is analyzed in terms of possible material mixing effects among others (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Low order rational values of the rotational transform -magnetic resonances, for brevity- can be present inside ECR-heated plasmas of the TJ-II Heliac, in low magnetic shear conditions, without causing damage to confine- ment. Moreover, in agreement with previous experience in the TJ-II, the resonances seem to benefit confinement and are associated to changes in the radial electric field, at least in the density gradient region. These results en- courage considering magnetic resonances as possible external actuators on confinement in stellarator/heliotron devices. c

The effect of the poloidal flow on the magnetic island is studied. The self-healing of the magnetic island has been observed in the Large Helical Device (LHD) and TJ-II. In TJ-II plasmas, the magnetic island is healed in case the radial electric field is positive. In the LHD experiment, on the other hand, the radial electric field is negative when the magnetic island is healed. The relation between the magnitudes of the E×B flow and ion diamagnetic flow is important to consider the effect of the poloidal flow on magnetic island (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Mean radial electric fields as well as low frequency Zonal Flow-like global oscillations in radial electric field have been identified during the low to high (L–H) transition in Hydrogen and Deuterium dominated plasmas in the stellarator TJ-II. No evidence of isotope effect on the L–H transition dynamics was observed in the investigated TJ-II plasma scenarios. These observations emphasize the critical role of both zero frequency (equilibrium) and low frequency varying large-scale flows for stabilizing turbulence during the triggering of the L–H transition in magnetically confined toroidal plasmas.

The antennas of the ITER plasma-position reflectometer are the components most exposed to the plasma. High thermal loads can cause high temperatures and excessive stress, so the first constrains on the antenna design arise from thermal simulations results. Therefore, the first step of the analysis is to develop a finite element thermal model with ANSYS. Once the temperatures are kept at acceptable levels, structural analysis is performed to know the thermal stress. Simulations performed using different materials and support structure geometries are discussed. Further, it has been checked that the components can withstand the electromagnetic loads expected during disruptions and vertical displacement events. The stress due to these electromagnetic loads is calculated analytically as well as with ANSYS simulations. The proposed antenna arrangement is properly designed against thermal and mechanical loads.