146 results on '"Rice, John E."'
Search Results
2. Recent Applications of FastFish-ID
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Wangh, Lawrence J., primary, Rice, John E., additional, and Sanchez, J. Aquiles, additional
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- 2024
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3. Linear-after-the-Exponential (LATE)-PCR: Primer Design Criteria for High Yields of Specific Single-Stranded DNA and Improved Real-Time Detection
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Pierce, Kenneth E., Sanchez, J. Aquiles, Rice, John E., Wangh, Lawrence J., and Petsko, Gregory A.
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- 2005
4. Linear-after-the-Exponential (LATE)-PCR: An Advanced Method of Asymmetric PCR and Its Uses in Quantitative Real-Time Analysis
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Sanchez, J. Aquiles, Pierce, Kenneth E., Rice, John E., Wangh, Lawrence J., and Petsko, Gregory A.
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- 2004
5. Comparison of core Ar17+ and Mo32+ toroidal rotation in C-Mod plasmas
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Rice, John E, primary, Angioni, Clemente, additional, Cao, Norman, additional, and Reinke, Matthew L, additional
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- 2023
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6. Closed-Tube Barcoding
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Sirianni, Nicky M., Yuan, Huijun, Rice, John E., Kaufman, Ronit S., Deng, John, Fulton, Chandler, and Wangh, Lawrence J.
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Nucleotide sequencing -- Methods ,DNA sequencing -- Methods ,Biological sciences - Abstract
Abstract: Here, we present a new approach for increasing the rate and lowering the cost of identifying, cataloging, and monitoring global biodiversity. These advances, which we call Closed-Tube Barcoding, are [...]
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- 2016
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7. Kin Recognition and Incest Avoidance in Toads
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Waldman, Bruce, Rice, John E., and Honeycutt, Rodney L.
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- 1992
8. Validation of FASTFISH-ID: A new commercial platform for rapid fish species authentication via universal closed-tube barcoding
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Naaum, Amanda M., primary, Cusa, Marine, additional, Singh, Maleeka, additional, Bleicher, Zoe, additional, Elliott, Christopher, additional, Goodhead, Ian B., additional, Hanner, Robert H., additional, Helyar, Sarah J., additional, Mariani, Stefano, additional, Rice, John E., additional, Wangh, Lawrence J., additional, and Sanchez, J. Aquiles, additional
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- 2021
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9. Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models
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Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Rodriguez Fernandez, Pablo, White, Anne E., Howard, Nathaniel Thomas, Rice, John E, Cao, Norman, Creely, Alexander James, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Irby, James Henderson, Sciortino, Francesco, Grierson, B. A., Staebler, G. M., Yuan, X., Creely, A. J., Greenwald, M. J., Rice, John E., Greenwald, Martin J., Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Rodriguez Fernandez, Pablo, White, Anne E., Howard, Nathaniel Thomas, Rice, John E, Cao, Norman, Creely, Alexander James, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Irby, James Henderson, Sciortino, Francesco, Grierson, B. A., Staebler, G. M., Yuan, X., Creely, A. J., Greenwald, M. J., Rice, John E., and Greenwald, Martin J.
- Abstract
A long-standing enigma in plasma transport has been resolved by modeling of cold-pulse experiments conducted on the Alcator C-Mod tokamak. Controlled edge cooling of fusion plasmas triggers core electron heating on time scales faster than an energy confinement time, which has long been interpreted as strong evidence of nonlocal transport. This Letter shows that the steady-state profiles, the cold-pulse rise time, and disappearance at higher density as measured in these experiments are successfully captured by a recent local quasilinear turbulent transport model, demonstrating that the existence of nonlocal transport phenomena is not necessary for explaining the behavior and time scales of cold-pulse experiments in tokamak plasmas., United States. Department of Energy (Award DE-FC02-99ER54512), United States. Department of Energy (Grant DESC0014264)
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- 2018
10. Applying X-ray Imaging Crystal Spectroscopy for Use as a High Temperature Plasma Diagnostic
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Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Cao, Norman, Mier, Andres M., Rice, John E, Rice, John E., Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Cao, Norman, Mier, Andres M., Rice, John E, and Rice, John E.
- Abstract
X-ray spectra provide a wealth of information on high temperature plasmas; for example electron temperature and density can be inferred from line intensity ratios. By using a Johann spectrometer viewing the plasma, it is possible to construct profiles of plasma parameters such as density, temperature, and velocity with good spatial and time resolution. However, benchmarking atomic code modeling of X-ray spectra obtained from well-diagnosed laboratory plasmas is important to justify use of such spectra to determine plasma parameters when other independent diagnostics are not available. This manuscript presents the operation of the High Resolution X-ray Crystal Imaging Spectrometer with Spatial Resolution (HIREXSR), a high wavelength resolution spatially imaging X-ray spectrometer used to view hydrogen- and helium-like ions of medium atomic number elements in a tokamak plasma. In addition, this manuscript covers a laser blow-off system that can introduce such ions to the plasma with precise timing to allow for perturbative studies of transport in the plasma. Keywords: Engineering, Issue 114, X-Ray Spectroscopy, Crystal Spectroscopy, Plasma Physics, Fusion, Tokamaks, Plasma Diagnostics, United States. Department of Energy (Contract DE-FC02-99ER54512), United States. Department of Energy (Contract DE-AC02-76CH03073)
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- 2018
11. Fluorescent signatures for variable DNA sequences
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Rice, John E., Reis, Arthur H., Jr, Rice, Lisa M., Carver-Brown, Rachel K., and Wangh, Lawrence J.
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- 2012
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12. Direct amplification of single-stranded DNA for pyrosequencing using linear-after-the-exponential (LATE)–PCR
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Salk, Jesse J., Sanchez, J. Aquiles, Pierce, Kenneth E., Rice, John E., Soares, Kevin C., and Wangh, Lawrence J.
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- 2006
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13. Dilute-‘N’-Go dideoxy sequencing of all DNA strands generated in multiplex LATE-PCR assays
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Jia, Yanwei, Osborne, Adam, Rice, John E., and Wangh, Lawrence J.
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- 2010
- Full Text
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14. Improved confinement in high-density H-modes via modification of the plasma boundary with Lower Hybrid RF
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Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Terry, James L, Reinke, Matthew Logan, Hughes Jr, Jerry, Labombard, Brian, Theiler, Christian, Wallace, Gregory Marriner, Baek, Seung Gyou, Brunner, Daniel Frederic, Churchill, Randy Michael, Edlund, Eric Matthias, Ennever, Paul Chappell, Faust, Ian Charles, Golfinopoulos, Theodore, Greenwald, Martin J, Hubbard, Amanda E, Irby, James Henderson, Lin, Yijun, Parker, Ronald R, Rice, John E, Shiraiwa, Shunichi, Walk Jr, John R, Wukitch, Stephen James, Xu, Peng, Churchill, Randy, Greenwald, Martin J., Parker, R., Rice, John E., Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Terry, James L, Reinke, Matthew Logan, Hughes Jr, Jerry, Labombard, Brian, Theiler, Christian, Wallace, Gregory Marriner, Baek, Seung Gyou, Brunner, Daniel Frederic, Churchill, Randy Michael, Edlund, Eric Matthias, Ennever, Paul Chappell, Faust, Ian Charles, Golfinopoulos, Theodore, Greenwald, Martin J, Hubbard, Amanda E, Irby, James Henderson, Lin, Yijun, Parker, Ronald R, Rice, John E, Shiraiwa, Shunichi, Walk Jr, John R, Wukitch, Stephen James, Xu, Peng, Churchill, Randy, Greenwald, Martin J., Parker, R., and Rice, John E.
- Abstract
Injecting Lower Hybrid Range of Frequency (LHRF) waves into Alcator C-Mod's high-density H-mode plasmas has led to enhanced global energy confinement by increasing pedestal temperature and pressure gradients, decreasing the separatrix density, modifying the pedestal radial electric field and rotation, and decreasing edge turbulence. These experiments indicate that edge LHRF can be used as an actuator to increase energy confinement via modification of boundary quantities. H98-factor increases of up to ∼35% (e.g., H₉₈ from 0.75 to 1.0) are seen when moderate amounts of LH power (P[subscript LH]/P[subscript tot] ∼ 0.15) are applied to H-modes of densities [n with line above it][subscript e] ∼ 3 × 10²⁰ m⁻³, corresponding to values ∼0.5 of the Greenwald density. However, the magnitude of the improvement is reduced if the confinement quality of the target H-mode plasma is already good (i.e., H₉₈ [superscript target] ∼ 1). Ray-tracing modeling and accessibility calculations for the LH waves indicate that they do not penetrate to the core. The LHRF power appears to be deposited in plasma boundary region, with a large fraction of the injected power increment appearing promptly on the outer divertor target. There is no evidence that the LH waves are driving current in these plasmas. The LHRF-actuated improvements are well correlated with suppressed pedestal density fluctuations in the 100–300 kHz range. There is also a correlation between the improved confinement and a drop in separatrix density, a correlation that is consistent with previous H-mode results with no LHRF., United States. Department of Energy. Office of Fusion Energy Sciences (Award DE-FC02-99ER54512), United States. Department of Energy. Office of Fusion Energy Sciences (Award DE-AC02-09CH11466)
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- 2017
15. Multispecies density peaking in gyrokinetic turbulence simulations of low collisionality Alcator C-Mod plasmas
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Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Greenwald, Martin J, Howard, Nathaniel Thomas, Hughes Jr, Jerry, Rice, John E, Reinke, Matthew Logan, Podpaly, Yuri A, Ma, Y., Mikkelsen, D. R., Bitter, M., Delgado-Aparicio, L., Hill, K. W., Candy, J., Waltz, R. E., Greenwald, Martin J., Rice, John E., Podpaly, Yuri, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Greenwald, Martin J, Howard, Nathaniel Thomas, Hughes Jr, Jerry, Rice, John E, Reinke, Matthew Logan, Podpaly, Yuri A, Ma, Y., Mikkelsen, D. R., Bitter, M., Delgado-Aparicio, L., Hill, K. W., Candy, J., Waltz, R. E., Greenwald, Martin J., Rice, John E., and Podpaly, Yuri
- Abstract
Peaked density profiles in low-collisionality AUG and JET H-mode plasmas are probably caused by a turbulently driven particle pinch, and Alcator C-Mod experiments confirmed that collisionality is a critical parameter. Density peaking in reactors could produce a number of important effects, some beneficial, such as enhanced fusion power and transport of fuel ions from the edge to the core, while others are undesirable, such as lower beta limits, reduced radiation from the plasma edge, and consequently higher divertor heat loads. Fundamental understanding of the pinch will enable planning to optimize these impacts. We show that density peaking is predicted by nonlinear gyrokinetic turbulence simulations based on measured profile data from low collisionality H-mode plasma in Alcator C-Mod. Multiple ion species are included to determine whether hydrogenic density peaking has an isotope dependence or is influenced by typical levels of low-Z impurities, and whether impurity density peaking depends on the species. We find that the deuterium density profile is slightly more peaked than that of hydrogen, and that experimentally relevant levels of boron have no appreciable effect on hydrogenic density peaking. The ratio of density at r/a = 0.44 to that at r/a = 0.74 is 1.2 for the majority D and minority H ions (and for electrons), and increases with impurity Z: 1.1 for helium, 1.15 for boron, 1.3 for neon, 1.4 for argon, and 1.5 for molybdenum. The ion temperature profile is varied to match better the predicted heat flux with the experimental transport analysis, but the resulting factor of two change in heat transport has only a weak effect on the predicted density peaking., United States. Department of Energy (Contract DE-AC02-09CH11466), United States. Department of Energy (Contract DE-FC02-99ER54512), United States. Department of Energy (Contract DE-FG02-95ER54309)
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- 2017
16. Alcator C-Mod: research in support of ITER and steps beyond
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Massachusetts Institute of Technology. Department of Biological Engineering, Massachusetts Institute of Technology. Department of Mathematics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson Ian, Baek, Seung Gyou, Marmar, Earl S, Barnard, Harold Salvadore, Bonoli, Paul T, Brunner, Daniel Frederic, Ennever, Paul Chappell, Fiore, Catherine L, Gao, Chi, Golfinopoulos, Theodore, Greenwald, Martin J, Hartwig, Zachary Seth, Hubbard, Amanda E, Hughes Jr, Jerry, Hutchinson, Ian Horner, Irby, James Henderson, Labombard, Brian, Lin, Yijun, Mumgaard, Robert Thomas, Parker, Ronald R, Porkolab, Miklos, Rice, John E, Shiraiwa, Shunichi, Sorbom, Brandon Nils, Terry, David Rankin, Terry, James L, Vieira, Rui F, Walk Jr, John R, Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G, Wolfe, Stephen M, Wright, John C, Wright, Graham, Wukitch, Stephen James, Xu, Peng, Cziegler, Istvan, Dekow, Gary L, Delgado-Aparicio, Luis, Lipschultz, Bruce, Theiler, Christian, Diallo, Ahmed Y, Edlund, Eric Matthias, Faust, Ian Charles, Candy, J., Canik, J., Churchill, R.M., Holland, C., Loarte, A., Reinke, M.L., Scott, S., Snyder, P., Theiler, C., Diallo, A., Edlund, E., LaBombard, B., Marmar, Earl S., Bonoli, Paul T., Fiore, Catherine, Greenwald, Martin J., Parker, R., Rice, John E., Wright, John C., Massachusetts Institute of Technology. Department of Biological Engineering, Massachusetts Institute of Technology. Department of Mathematics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson Ian, Baek, Seung Gyou, Marmar, Earl S, Barnard, Harold Salvadore, Bonoli, Paul T, Brunner, Daniel Frederic, Ennever, Paul Chappell, Fiore, Catherine L, Gao, Chi, Golfinopoulos, Theodore, Greenwald, Martin J, Hartwig, Zachary Seth, Hubbard, Amanda E, Hughes Jr, Jerry, Hutchinson, Ian Horner, Irby, James Henderson, Labombard, Brian, Lin, Yijun, Mumgaard, Robert Thomas, Parker, Ronald R, Porkolab, Miklos, Rice, John E, Shiraiwa, Shunichi, Sorbom, Brandon Nils, Terry, David Rankin, Terry, James L, Vieira, Rui F, Walk Jr, John R, Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G, Wolfe, Stephen M, Wright, John C, Wright, Graham, Wukitch, Stephen James, Xu, Peng, Cziegler, Istvan, Dekow, Gary L, Delgado-Aparicio, Luis, Lipschultz, Bruce, Theiler, Christian, Diallo, Ahmed Y, Edlund, Eric Matthias, Faust, Ian Charles, Candy, J., Canik, J., Churchill, R.M., Holland, C., Loarte, A., Reinke, M.L., Scott, S., Snyder, P., Theiler, C., Diallo, A., Edlund, E., LaBombard, B., Marmar, Earl S., Bonoli, Paul T., Fiore, Catherine, Greenwald, Martin J., Parker, R., Rice, John E., and Wright, John C.
- Abstract
This paper presents an overview of recent highlights from research on Alcator C-Mod. Significant progress has been made across all research areas over the last two years, with particular emphasis on divertor physics and power handling, plasma–material interaction studies, edge localized mode-suppressed pedestal dynamics, core transport and turbulence, and RF heating and current drive utilizing ion cyclotron and lower hybrid tools. Specific results of particular relevance to ITER include: inner wall SOL transport studies that have led, together with results from other experiments, to the change of the detailed shape of the inner wall in ITER; runaway electron studies showing that the critical electric field required for runaway generation is much higher than predicted from collisional theory; core tungsten impurity transport studies reveal that tungsten accumulation is naturally avoided in typical C-Mod conditions., United States. Department of Energy (DE-FC02-99ER54512-CMOD), United States. Department of Energy (DE-AC02-09CH11466), United States. Department of Energy (DE-FG02-96ER-54373), United States. Department of Energy (DE-FG02-94ER54235)
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- 2017
17. Tungsten impurity transport experiments in Alcator C-Mod to address high priority research and development for ITER
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Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Chilenski, Mark Alan, Howard, Nathaniel Thomas, Hubbard, Amanda E, Hughes Jr, Jerry, Rice, John E, Walk Jr, John R, Loarte, A., Reinke, M. L., Polevoi, A. R., Hosokawa, M., Köchl, F., Pütterich, T., Dux, R., Zhogolev, V. E., Rice, John E., Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Chilenski, Mark Alan, Howard, Nathaniel Thomas, Hubbard, Amanda E, Hughes Jr, Jerry, Rice, John E, Walk Jr, John R, Loarte, A., Reinke, M. L., Polevoi, A. R., Hosokawa, M., Köchl, F., Pütterich, T., Dux, R., Zhogolev, V. E., and Rice, John E.
- Abstract
Experiments in Alcator C-Mod tokamak plasmas in the Enhanced D-alpha H-mode regime with ITER-like mid-radius plasma density peaking and Ion Cyclotron Resonant heating, in which tungsten is introduced by the laser blow-off technique, have demonstrated that accumulation of tungsten in the central region of the plasma does not take place in these conditions. The measurements obtained are consistent with anomalous transport dominating tungsten transport except in the central region of the plasma where tungsten transport is neoclassical, as previously observed in other devices with dominant neutral beam injection heating, such as JET and ASDEX Upgrade. In contrast to such results, however, the measured scale lengths for plasma temperature and density in the central region of these Alcator C-Mod plasmas, with density profiles relatively flat in the core region due to the lack of core fuelling, are favourable to prevent inter and intra sawtooth tungsten accumulation in this region under dominance of neoclassical transport. Simulations of ITER H-mode plasmas, including both anomalous (modelled by the Gyro-Landau-Fluid code GLF23) and neoclassical transport for main ions and tungsten and with density profiles of similar peaking to those obtained in Alcator C-Mod show that accumulation of tungsten in the central plasma region is also unlikely to occur in stationary ITER H-mode plasmas due to the low fuelling source by the neutral beam injection (injection energy ∼ 1 MeV), which is in good agreement with findings in the Alcator C-Mod experiments., United States. Department of Energy (DE-FC02-99ER54512)
- Published
- 2017
18. Nonlinear gyrokinetic simulations of the I-mode high confinement regime and comparisons with experimenta)
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Lincoln Laboratory, Massachusetts Institute of Technology. Department of Mathematics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis, White, Anne E., Howard, Nathaniel Thomas, Creely, Alexander James, Chilenski, Mark Alan, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Marmar, Earl S, Rice, John E, Sierchio, Jennifer M., Sung, Choongki, Walk Jr, John R, Whyte, Dennis G, Mikkelsen, David, Edlund, Eric Matthias, Kung, Chun C, Petty, Clinton C., Reinke, Matthew Logan, Theiler, Christian, Holland, C., Candy, J., Theiler, C., Greenwald, Martin J., Marmar, Earl S., Rice, John E., Lincoln Laboratory, Massachusetts Institute of Technology. Department of Mathematics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis, White, Anne E., Howard, Nathaniel Thomas, Creely, Alexander James, Chilenski, Mark Alan, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Marmar, Earl S, Rice, John E, Sierchio, Jennifer M., Sung, Choongki, Walk Jr, John R, Whyte, Dennis G, Mikkelsen, David, Edlund, Eric Matthias, Kung, Chun C, Petty, Clinton C., Reinke, Matthew Logan, Theiler, Christian, Holland, C., Candy, J., Theiler, C., Greenwald, Martin J., Marmar, Earl S., and Rice, John E.
- Abstract
For the first time, nonlinear gyrokinetic simulations of I-mode plasmas are performed and compared with experiment. I-mode is a high confinement regime, featuring energy confinement similar to H-mode, but without enhanced particle and impurity particle confinement [D. G. Whyte et al., Nucl. Fusion 50, 105005 (2010)]. As a consequence of the separation between heat and particle transport, I-mode exhibits several favorable characteristics compared to H-mode. The nonlinear gyrokinetic code GYRO [J. Candy and R. E. Waltz, J Comput. Phys. 186, 545 (2003)] is used to explore the effects of E × B shear and profile stiffness in I-mode and compare with L-mode. The nonlinear GYRO simulations show that I-mode core ion temperature and electron temperature profiles are more stiff than L-mode core plasmas. Scans of the input E × B shear in GYRO simulations show that E × B shearing of turbulence is a stronger effect in the core of I-mode than L-mode. The nonlinear simulations match the observed reductions in long wavelength density fluctuation levels across the L-I transition but underestimate the reduction of long wavelength electron temperature fluctuation levels. The comparisons between experiment and gyrokinetic simulations for I-mode suggest that increased E × B shearing of turbulence combined with increased profile stiffness are responsible for the reductions in core turbulence observed in the experiment, and that I-mode resembles H-mode plasmas more than L-mode plasmas with regards to marginal stability and temperature profile stiffness., United States. Department of Energy (Contract No. DE-FC02-99ER54512-CMOD), United States. Department of Energy. Office of Science (Contract No. DE-AC02- 05CH11231)
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- 2017
19. Multiple and Ancient Origins of the Domestic Dog
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Vila, Carles, Savolainen, Peter, Maldonado, Jesus E., Amorim, Isabel R., Rice, John E., Honeycutt, Rodney L., Crandall, Keith A., Lundeberg, Joakim, and Wayne, Robert K.
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- 1997
20. Taxonomy of the Iberian lynx
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Beltran, Juan F., Rice, John E., and Honeycutt, Rodney L.
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- 1996
21. Towards an Emerging Understanding of Non-local Transport
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Massachusetts Institute of Technology. Plasma Science and Fusion Center, Rice, John E, Ida, K., Shi, Z., Sun, H.J., Inagaki, S., Kamiya, K., Tamura, N., Diamond, P.H., Dif-Pradalier, G., Zou, X.L., Itoh, K., Sugita, S., Gurcan, O.D., Estrada, T., Hidalgo, C., Hahm, T.S., Stroth, U., Field, A., Ding, X.T., Sakamoto, Y., Oldenburger, S., Yoshinuma, M., Kobayashi, T., Jiang, M., Hahn, S.H., Jeon, Y.M., Hong, S. H., Dong, J., Itoh, S.-I., Massachusetts Institute of Technology. Plasma Science and Fusion Center, Rice, John E, Ida, K., Shi, Z., Sun, H.J., Inagaki, S., Kamiya, K., Tamura, N., Diamond, P.H., Dif-Pradalier, G., Zou, X.L., Itoh, K., Sugita, S., Gurcan, O.D., Estrada, T., Hidalgo, C., Hahm, T.S., Stroth, U., Field, A., Ding, X.T., Sakamoto, Y., Oldenburger, S., Yoshinuma, M., Kobayashi, T., Jiang, M., Hahn, S.H., Jeon, Y.M., Hong, S. H., Dong, J., and Itoh, S.-I.
- Abstract
In this overview, recent progress on the experimental analysis and theoretical models for non-local transport (non-Fickian fluxes in real space) are overviewed. The non-locality in the heat and momentum transport observed in the plasma, the departures from linear fluxgradient proportionality and spontaneously and externally triggered non-local transport phenomena will be described in both L-mode and improved-mode plasmas. We will report on ongoing evaluation of "fast front" and "intrinsically nonlocal" models, and their success in comparisons with experimental data.
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- 2018
22. ICRF mode conversion in three-ion species heating experiment and in flow drive experiment on the Alcator C-Mod tokamak
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Massachusetts Institute of Technology. Plasma Science and Fusion Center, Lin, Yijun, Wukitch, Stephen James, Edlund, Eric Matthias, Ennever, Paul Chappell, Hubbard, Amanda E, Porkolab, Miklos, Rice, John E, Wright, John C, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Lin, Yijun, Wukitch, Stephen James, Edlund, Eric Matthias, Ennever, Paul Chappell, Hubbard, Amanda E, Porkolab, Miklos, Rice, John E, and Wright, John C
- Abstract
In recent three-ion species (majority D and H plus a trace level of 3 He) ICRF heating experiments on Alcator C-Mod, double mode conversion on both sides of the 3 He cyclotron resonance has been observed using the phase contrast imaging (PCI) system. The MC locations are used to estimate the species concentrations in the plasma. Simulation using TORIC shows that with the 3 He level < 1%, most RF power is absorbed by the 3 He ions and the process can generate energetic 3 He ions. In mode conversion (MC) flow drive experiment in D( 3 He) plasma at 8 T, MC waves were also monitored by PCI. The MC ion cyclotron wave (ICW) amplitude and wavenumber k R have been found to correlate with the flow drive force. The MC efficiency, wave-number k of the MC ICW and their dependence on plasma parameters like T e0 have been studied. Based on the experimental observation and numerical study of the dispersion solutions, a hypothesis of the flow drive mechanism has been proposed., United States. Department of Energy. Office of Fusion Energy Sciences (Award DE -FC02 -99ER54512)
- Published
- 2018
23. Non-resonant destabilization of (1/1) internal kink mode by suprathermal electron pressure
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Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Shiraiwa, Shunichi, Irby, James Henderson, Granetz, Robert S, Parker, Ronald R, Baek, Seung Gyou, Faust, Ian Charles, Wallace, Gregory Marriner, Mumgaard, Robert Thomas, Gao, Chi, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Marmar, Earl S, Rice, John E, Wolfe, Stephen M, Delgado-Aparicio, L., Sugiyama, L., Gates, D. A., Gorelenkov, N., Scott, S., Bertelli, N., Phillips, P. E., Rowan, W. L., Wilson, R., Wukitch, S., Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Shiraiwa, Shunichi, Irby, James Henderson, Granetz, Robert S, Parker, Ronald R, Baek, Seung Gyou, Faust, Ian Charles, Wallace, Gregory Marriner, Mumgaard, Robert Thomas, Gao, Chi, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Marmar, Earl S, Rice, John E, Wolfe, Stephen M, Delgado-Aparicio, L., Sugiyama, L., Gates, D. A., Gorelenkov, N., Scott, S., Bertelli, N., Phillips, P. E., Rowan, W. L., Wilson, R., and Wukitch, S.
- Abstract
New experimental observations are reported on the structure and dynamics of short-lived periodic (1, 1) "fishbone"-like oscillations that appear during radio frequency heating and current-drive experiments in tokamak plasmas. For the first time, measurements can directly relate changes in the high energy electrons to the mode onset, saturation, and damping. In the relatively high collisionality of Alcator C-Mod with lower hybrid current drive, the instability appears to be destabilized by the non-resonant suprathermal electro n pressure - rather than by wave-particle resonance, rotates toroidally with the plasma and grows independently of the (1, 1) sawtooth crash driven by the thermal plasma pressure., United States. Department of Energy (Contract DE-FC02-99ER54512), United States. Department of Energy (Contract DE-SC0007883)
- Published
- 2018
24. Experimentally testing the dependence of momentum transport on second derivatives using Gaussian process regression
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Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Chilenski, Mark Alan, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Lee, J. P., Marzouk, Youssef M, Rice, John E, White, Anne E., Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Chilenski, Mark Alan, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Lee, J. P., Marzouk, Youssef M, Rice, John E, and White, Anne E.
- Abstract
It remains an open question to explain the dramatic change in intrinsic rotation induced by slight changes in electron density (White et al 2013 Phys. Plasmas 20 056106). One proposed explanation is that momentum transport is sensitive to the second derivatives of the temperature and density profiles (Lee et al 2015 Plasma Phys. Control. Fusion 57 125006), but it is widely considered to be impossible to measure these higher derivatives. In this paper, we show that it is possible to estimate second derivatives of electron density and temperature using a nonparametric regression technique known as Gaussian process regression. This technique avoids over-constraining the fit by not assuming an explicit functional form for the fitted curve. The uncertainties, obtained rigorously using Markov chain Monte Carlo sampling, are small enough that it is reasonable to explore hypotheses which depend on second derivatives. It is found that the differences in the second derivatives of and between the peaked and hollow rotation cases are rather small, suggesting that changes in the second derivatives are not likely to explain the experimental results.
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- 2018
25. Two-temperature LATE-PCR endpoint genotyping
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Reis Arthur H, Salk Jesse J, Abramowitz Jessica D, Sanchez J Aquiles, Rice John E, Pierce Kenneth E, and Wangh Lawrence J
- Subjects
Biotechnology ,TP248.13-248.65 - Abstract
Abstract Background In conventional PCR, total amplicon yield becomes independent of starting template number as amplification reaches plateau and varies significantly among replicate reactions. This paper describes a strategy for reconfiguring PCR so that the signal intensity of a single fluorescent detection probe after PCR thermal cycling reflects genomic composition. The resulting method corrects for product yield variations among replicate amplification reactions, permits resolution of homozygous and heterozygous genotypes based on endpoint fluorescence signal intensities, and readily identifies imbalanced allele ratios equivalent to those arising from gene/chromosomal duplications. Furthermore, the use of only a single colored probe for genotyping enhances the multiplex detection capacity of the assay. Results Two-Temperature LATE-PCR endpoint genotyping combines Linear-After-The-Exponential (LATE)-PCR (an advanced form of asymmetric PCR that efficiently generates single-stranded DNA) and mismatch-tolerant probes capable of detecting allele-specific targets at high temperature and total single-stranded amplicons at a lower temperature in the same reaction. The method is demonstrated here for genotyping single-nucleotide alleles of the human HEXA gene responsible for Tay-Sachs disease and for genotyping SNP alleles near the human p53 tumor suppressor gene. In each case, the final probe signals were normalized against total single-stranded DNA generated in the same reaction. Normalization reduces the coefficient of variation among replicates from 17.22% to as little as 2.78% and permits endpoint genotyping with >99.7% accuracy. These assays are robust because they are consistent over a wide range of input DNA concentrations and give the same results regardless of how many cycles of linear amplification have elapsed. The method is also sufficiently powerful to distinguish between samples with a 1:1 ratio of two alleles from samples comprised of 2:1 and 1:2 ratios of the same alleles. Conclusion SNP genotyping via Two-Temperature LATE-PCR takes place in a homogeneous closed-tube format and uses a single hybridization probe per SNP site. These assays are convenient, rely on endpoint analysis, improve the options for construction of multiplex assays, and are suitable for SNP genotyping, mutation scanning, and detection of DNA duplication or deletions.
- Published
- 2006
- Full Text
- View/download PDF
26. Alcator C-Mod: research in support of ITER and steps beyond
- Author
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Candy, J., Canik, J., Churchill, R.M., Holland, C., Loarte, A., Reinke, M.L., Scott, S., Snyder, P., Theiler, C., Diallo, A., Edlund, E., LaBombard, B., Baek, Seung Gyou, Marmar, Earl S, Barnard, Harold Salvadore, Bonoli, Paul T, Brunner, Daniel Frederic, Ennever, Paul Chappell, Fiore, Catherine L, Gao, Chi, Golfinopoulos, Theodore, Greenwald, Martin J, Hartwig, Zachary Seth, Hubbard, Amanda E, Hughes Jr, Jerry, Hutchinson, Ian Horner, Irby, James Henderson, Labombard, Brian, Lin, Yijun, Mumgaard, Robert Thomas, Parker, Ronald R, Porkolab, Miklos, Rice, John E, Shiraiwa, Shunichi, Sorbom, Brandon Nils, Terry, David Rankin, Terry, James L, Vieira, Rui F, Walk Jr, John R, Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G, Wolfe, Stephen M, Wright, John C, Wright, Graham, Wukitch, Stephen James, Xu, Peng, Cziegler, Istvan, Dekow, Gary L, Delgado-Aparicio, Luis, Lipschultz, Bruce, Theiler, Christian, Diallo, Ahmed Y, Edlund, Eric Matthias, Faust, Ian Charles, Massachusetts Institute of Technology. Department of Biological Engineering, Massachusetts Institute of Technology. Department of Mathematics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson Ian, Baek, Seung Gyou, Marmar, Earl S, Barnard, Harold Salvadore, Bonoli, Paul T, Brunner, Daniel Frederic, Ennever, Paul Chappell, Fiore, Catherine L, Gao, Chi, Golfinopoulos, Theodore, Greenwald, Martin J, Hartwig, Zachary Seth, Hubbard, Amanda E, Hughes Jr, Jerry, Hutchinson, Ian Horner, Irby, James Henderson, Labombard, Brian, Lin, Yijun, Mumgaard, Robert Thomas, Parker, Ronald R, Porkolab, Miklos, Rice, John E, Shiraiwa, Shunichi, Sorbom, Brandon Nils, Terry, David Rankin, Terry, James L, Vieira, Rui F, Walk Jr, John R, Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G, Wolfe, Stephen M, Wright, John C, Wright, Graham, Wukitch, Stephen James, Xu, Peng, Cziegler, Istvan, Dekow, Gary L, Delgado-Aparicio, Luis, Lipschultz, Bruce, Theiler, Christian, Diallo, Ahmed Y, Edlund, Eric Matthias, and Faust, Ian Charles
- Subjects
Nuclear and High Energy Physics ,Materials science ,Tokamak ,Divertor ,Nuclear engineering ,Cyclotron ,FEC 2014 ,chemistry.chemical_element ,overview ,Electron ,Tungsten ,Condensed Matter Physics ,law.invention ,Pedestal ,Alcator C-Mod ,chemistry ,law ,Dielectric heating ,Atomic physics ,tokamak - Abstract
This paper presents an overview of recent highlights from research on Alcator C-Mod. Significant progress has been made across all research areas over the last two years, with particular emphasis on divertor physics and power handling, plasma–material interaction studies, edge localized mode-suppressed pedestal dynamics, core transport and turbulence, and RF heating and current drive utilizing ion cyclotron and lower hybrid tools. Specific results of particular relevance to ITER include: inner wall SOL transport studies that have led, together with results from other experiments, to the change of the detailed shape of the inner wall in ITER; runaway electron studies showing that the critical electric field required for runaway generation is much higher than predicted from collisional theory; core tungsten impurity transport studies reveal that tungsten accumulation is naturally avoided in typical C-Mod conditions., United States. Department of Energy (DE-FC02-99ER54512-CMOD), United States. Department of Energy (DE-AC02-09CH11466), United States. Department of Energy (DE-FG02-96ER-54373), United States. Department of Energy (DE-FG02-94ER54235)
- Published
- 2015
27. EUV Spectra and Line Ratios of Multiply Ionized Calcium and Argon Atoms in a Laboratory Plasma
- Author
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Träbert, Elmar, primary, Beiersdorfer, Peter, additional, Lepson, Jaan K., additional, Reinke, Matthew L., additional, and Rice, John E., additional
- Published
- 2018
- Full Text
- View/download PDF
28. Diagnostic Accuracy and Utility of FluoroType MTBDR, a New Molecular Assay for Multidrug-Resistant Tuberculosis
- Author
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de Vos, Margaretha, primary, Derendinger, Brigitta, additional, Dolby, Tania, additional, Simpson, John, additional, van Helden, Paul D., additional, Rice, John E., additional, Wangh, Lawrence J., additional, Theron, Grant, additional, and Warren, Robin M., additional
- Published
- 2018
- Full Text
- View/download PDF
29. Multi-device studies of pedestal physics and confinement in the I-mode regime
- Author
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Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis, Hubbard, Amanda E, Hughes Jr, Jerry, Marinoni, Alessandro, Marmar, Earl S, Rice, John E, Walk Jr, John R, Whyte, Dennis G, Wolfe, Stephen M, Osborne, T., Ryter, F., Austin, M., Barrera Orte, L., Churchill, R. M., Cziegler, I., Fenstermacher, M., Fischer, R., Gerhardt, S., Groebner, R., Gohil, P., Happel, T., Loarte, A., Maingi, R., Manz, P., McDermott, R. M., McKee, G., Rhodes, T. L., Schmitz, L., Theiler, C., Viezzer, E., Walk, J. R., Wolfrum, E., Yan, Z., Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis, Hubbard, Amanda E, Hughes Jr, Jerry, Marinoni, Alessandro, Marmar, Earl S, Rice, John E, Walk Jr, John R, Whyte, Dennis G, Wolfe, Stephen M, Osborne, T., Ryter, F., Austin, M., Barrera Orte, L., Churchill, R. M., Cziegler, I., Fenstermacher, M., Fischer, R., Gerhardt, S., Groebner, R., Gohil, P., Happel, T., Loarte, A., Maingi, R., Manz, P., McDermott, R. M., McKee, G., Rhodes, T. L., Schmitz, L., Theiler, C., Viezzer, E., Walk, J. R., Wolfrum, E., and Yan, Z.
- Abstract
This paper describes joint ITPA studies of the I-mode regime, which features an edge thermal barrier together with L-mode-like particle and impurity transport and no edge localized modes (ELMs). The regime has been demonstrated on the Alcator C-Mod, ASDEX Upgrade and DIII-D tokamaks, over a wide range of device parameters and pedestal conditions. Dimensionless parameters at the pedestal show overlap across devices and extend to low collisionality. When they are matched, pedestal temperature profiles are also similar. Pedestals are stable to peeling–ballooning modes, consistent with lack of ELMs. Access to I-mode is independent of heating method (neutral beam injection, ion cyclotron and/or electron cyclotron resonance heating). Normalized energy confinement H 98,y2 ≥ 1 has been achieved for a range of 3 ≤ q 95 ≤ 4.9 and scales favourably with power. Changes in turbulence in the pedestal region accompany the transition from L-mode to I-mode. The L–I threshold increases with plasma density and current, and with device size, but has a weak dependence on toroidal magnetic field B T. The upper limit of power for I-modes, which is set by I–H transitions, increases with B T and the power range is largest on Alcator C-Mod at B > 5 T. Issues for extrapolation to ITER and other future fusion devices are discussed., United States. Department of Energy (DE-FC02-99ER54512-CMOD), United States. Department of Energy (DE-SC0012469), United States. Department of Energy (DE-FC02-04ER54698), United States. Department of Energy (DE-FG02-94ER54235), United States. Department of Energy (DE-AC52-07NA27344), United States. Department of Energy (DE-AC02-09CH11466), United States. Department of Energy (DE-FG02-89ER53296), United States. Department of Energy (DE-FG02-08ER54999), United States. Department of Energy (DE-FG02-08ER54984)
- Published
- 2017
30. Impurity transport, turbulence transitions and intrinsic rotation in Alcator C-Mod plasmas
- Author
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Massachusetts Institute of Technology. Plasma Science and Fusion Center, White, Anne, White, Anne E., Greenwald, Martin J, Rice, John E, Holland, C., Howard, N. T., Massachusetts Institute of Technology. Plasma Science and Fusion Center, White, Anne, White, Anne E., Greenwald, Martin J, Rice, John E, Holland, C., and Howard, N. T.
- Abstract
Linear and nonlinear gyrokinetic simulations are used to probe turbulent impurity transport in intrinsically rotating tokamak plasmas. For this simulation-based study, experimental input parameters are taken from a pair of ICRF heated Alcator C-Mod discharges exhibiting a change in the sign of the normalized toroidal rotation gradient at mid-radius (i.e. a change from hollow to peaked intrinsic rotation profiles). The simulations show that there is no change in the peaking of the calcium impurity between the plasmas with peaked and hollow rotation profiles, suggesting that the impurity transport and the shape of the rotation do not always change together. Furthermore, near mid-radius, r/a = 0.5 (normalized midplane minor radius), the linear and nonlinear gyrokinetic simulations exhibit no evidence of a transition from ion temperature gradient (ITG) to trapped electron mode dominance when the intrinsic rotation profile changes from peaked to hollow. Extensive nonlinear sensitivity analysis is performed, and there is no change in the ITG critical gradient or in the stiffness of ion heat transport with the change in the intrinsic toroidal rotation profile shape, which suggests that the shape of the rotation profile is not dominated by the ITG onset in these cases., United States. Department of Energy (contract DE-FC02-99ER54512-CMOD), United States. Department of Energy (Fusion Energy Postdoctoral Research Program)
- Published
- 2017
31. Nonlinear gyrokinetic simulations of the I-mode high confinement regime and comparisons with experimenta)
- Author
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Massachusetts Institute of Technology. Plasma Science and Fusion Center, White, Anne, White, Anne E., Howard, Nathaniel Thomas, Creely, Alexander James, Chilenski, Mark Alan, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Marmar, Earl S, Rice, John E, Sierchio, Jennifer M., Sung, Choongki, Walk Jr, John R, Whyte, Dennis G, Mikkelsen, D. R., Edlund, E. M., Kung, C., Holland, C., Candy, J., Petty, C. C., Reinke, M. L., Theiler, C., Massachusetts Institute of Technology. Plasma Science and Fusion Center, White, Anne, White, Anne E., Howard, Nathaniel Thomas, Creely, Alexander James, Chilenski, Mark Alan, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Marmar, Earl S, Rice, John E, Sierchio, Jennifer M., Sung, Choongki, Walk Jr, John R, Whyte, Dennis G, Mikkelsen, D. R., Edlund, E. M., Kung, C., Holland, C., Candy, J., Petty, C. C., Reinke, M. L., and Theiler, C.
- Abstract
For the first time, nonlinear gyrokinetic simulations of I-mode plasmas are performed and compared with experiment. I-mode is a high confinement regime, featuring energy confinement similar to H-mode, but without enhanced particle and impurity particle confinement [D. G. Whyte et al., Nucl. Fusion 50, 105005 (2010)]. As a consequence of the separation between heat and particle transport, I-mode exhibits several favorable characteristics compared to H-mode. The nonlinear gyrokinetic code GYRO [J. Candy and R. E. Waltz, J Comput. Phys. 186, 545 (2003)] is used to explore the effects of E × B shear and profile stiffness in I-mode and compare with L-mode. The nonlinear GYRO simulations show that I-mode core ion temperature and electron temperature profiles are more stiff than L-mode core plasmas. Scans of the input E × B shear in GYRO simulations show that E × B shearing of turbulence is a stronger effect in the core of I-mode than L-mode. The nonlinear simulations match the observed reductions in long wavelength density fluctuation levels across the L-I transition but underestimate the reduction of long wavelength electron temperature fluctuation levels. The comparisons between experiment and gyrokinetic simulations for I-mode suggest that increased E × B shearing of turbulence combined with increased profile stiffness are responsible for the reductions in core turbulence observed in the experiment, and that I-mode resembles H-mode plasmas more than L-mode plasmas with regards to marginal stability and temperature profile stiffness.
- Published
- 2017
32. The effects of main-ion dilution on turbulence in low q[subscript 95] C-Mod ohmic plasmas, and comparisons with nonlinear GYRO
- Author
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Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Ennever, Paul Chappell, Porkolab, Miklos, Rice, John E, Rost, Jon C, Ernst, Darin R, Hughes Jr, Jerry, Baek, Seung Gyou, Candy, J., Staebler, G., Reinke, M. L, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Ennever, Paul Chappell, Porkolab, Miklos, Rice, John E, Rost, Jon C, Ernst, Darin R, Hughes Jr, Jerry, Baek, Seung Gyou, Candy, J., Staebler, G., and Reinke, M. L
- Abstract
Recent experiments on C-mod seeding nitrogen into ohmic plasmas with [subscript q]95 = 3.4 found that the seeding greatly reduced long-wavelength (ITG-scale) turbulence. The long-wavelength turbulence that was reduced by the nitrogen seeding was localized to the region of r/a≈0.85, where the turbulence is well above marginal stability (as evidenced by Q[subscript i]/Q[subscript GB]≫1). The nonlinear gyrokinetic code GYRO was used to simulate the expected turbulence in these plasmas, and the simulated turbulent density fluctuations and turbulent energy fluxes quantitatively agreed with the experimental measurements both before and after the nitrogen seeding. Unexpectedly, the intrinsic rotation of the plasma was also found to be affected by the nitrogen seeding, in a manner apparently unrelated to a change in the electron-ion collisionality that was proposed by other experiments., United States. Dept. of Energy. Office of Fusion Energy Sciences (Award E-FG02-94-ER54235)
- Published
- 2017
33. Operating Experiences with Detergents at Washington, D. C. [with Discussion]
- Author
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Fuhrman, Ralph E., Rice, John E., Greeley, Samuel A., and Berg, Harvey E.
- Published
- 1953
34. Improved profile fitting and quantification of uncertainty in experimental measurements of impurity transport coefficients using Gaussian process regression
- Author
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Chilenski, Mark Alan, Greenwald, Martin J., Marzouk, Youssef M., Howard, Nathaniel Thomas, White, Anne E., Rice, John E., Walk, John R., Jr., Walk Jr., John R., Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Chilenski, Mark Alan, Greenwald, Martin J., Marzouk, Youssef M., Howard, Nathaniel Thomas, White, Anne E., Rice, John E., and Walk Jr., John R.
- Subjects
Nuclear and High Energy Physics ,Propagation of uncertainty ,Quality (physics) ,Rate of convergence ,Kriging ,Computer science ,Ground-penetrating radar ,Context (language use) ,Statistical physics ,Sensitivity (control systems) ,Condensed Matter Physics ,Regression - Abstract
The need to fit smooth temperature and density profiles to discrete observations is ubiquitous in plasma physics, but the prevailing techniques for this have many shortcomings that cast doubt on the statistical validity of the results. This issue is amplified in the context of validation of gyrokinetic transport models (Holland et al 2009 Phys. Plasmas 16 052301), where the strong sensitivity of the code outputs to input gradients means that inadequacies in the profile fitting technique can easily lead to an incorrect assessment of the degree of agreement with experimental measurements. In order to rectify the shortcomings of standard approaches to profile fitting, we have applied Gaussian process regression (GPR), a powerful non-parametric regression technique, to analyse an Alcator C-Mod L-mode discharge used for past gyrokinetic validation work (Howard et al 2012 Nucl. Fusion 52 063002). We show that the GPR techniques can reproduce the previous results while delivering more statistically rigorous fits and uncertainty estimates for both the value and the gradient of plasma profiles with an improved level of automation. We also discuss how the use of GPR can allow for dramatic increases in the rate of convergence of uncertainty propagation for any code that takes experimental profiles as inputs. The new GPR techniques for profile fitting and uncertainty propagation are quite useful and general, and we describe the steps to implementation in detail in this paper. These techniques have the potential to substantially improve the quality of uncertainty estimates on profile fits and the rate of convergence of uncertainty propagation, making them of great interest for wider use in fusion experiments and modelling efforts., United States. Dept. of Energy. Office of Fusion Energy Sciences (Award DE-FC02-99ER54512), United States. Dept. of Energy. Office of Science (Contract DE-AC05-06OR23177), United States. Dept. of Energy. Office of Advanced Scientific Computing Research (Award DE-SC0007099)
- Published
- 2015
35. Applying X-ray Imaging Crystal Spectroscopy for Use as a High Temperature Plasma Diagnostic
- Author
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Cao, Norman M., primary, Mier Valdivia, Andrés M., primary, and Rice, John E., primary
- Published
- 2016
- Full Text
- View/download PDF
36. Non-local heat transport in Alcator C-Mod ohmic L-mode plasmas
- Author
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Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Gao, Chi, Rice, John E., Reinke, Matthew Logan, Howard, Nathaniel Thomas, Hubbard, Amanda E., Chilenski, Mark Alan, Walk Jr, John R., Hughes, Jerry W., Jr., Ennever, Paul Chappell, Porkolab, Miklos, White, Anne E., Sung, Choongki, Delgado-Aparicio, Luis, Baek, Seung Gyou, Rowan, William L., Greenwald, Martin J., Granetz, Robert S., Wolfe, Stephen M., Marmar, Earl S., Sun, H. J., Mikkelson, D., Brookman, M. W., Alcator C-Mod Team, Gao, Chi, Ph. D. Massachusetts Institute of Technology, Hughes, Jerry W., Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Gao, Chi, Rice, John E., Reinke, Matthew Logan, Howard, Nathaniel Thomas, Hubbard, Amanda E., Chilenski, Mark Alan, Walk Jr, John R., Hughes, Jerry W., Jr., Ennever, Paul Chappell, Porkolab, Miklos, White, Anne E., Sung, Choongki, Delgado-Aparicio, Luis, Baek, Seung Gyou, Rowan, William L., Greenwald, Martin J., Granetz, Robert S., Wolfe, Stephen M., Marmar, Earl S., Sun, H. J., Mikkelson, D., Brookman, M. W., Alcator C-Mod Team, Gao, Chi, Ph. D. Massachusetts Institute of Technology, and Hughes, Jerry W.
- Abstract
Non-local heat transport experiments were performed in Alcator C-Mod ohmic L-mode plasmas by inducing edge cooling with laser blow-off impurity (CaF2) injection. The non-local effect, a cooling of the edge electron temperature with a rapid rise of the central electron temperature, which contradicts the assumption of 'local' transport, was observed in low collisionality linear ohmic confinement (LOC) regime plasmas. Transport analysis shows this phenomenon can be explained either by a fast drop of the core diffusivity, or the sudden appearance of a heat pinch. In high collisionality saturated ohmic confinement (SOC) regime plasmas, the thermal transport becomes 'local': the central electron temperature drops on the energy confinement time scale in response to the edge cooling. Measurements from a high resolution imaging x-ray spectrometer show that the ion temperature has a similar behaviour as the electron temperature in response to edge cooling, and that the transition density of non-locality correlates with the rotation reversal critical density. This connection may indicate the possible connection between thermal and momentum transport, which is also linked to a transition in turbulence dominance between trapped electron modes (TEMs) and ion temperature gradient (ITG) modes. Experiments with repetitive cold pulses in one discharge were also performed to allow Fourier analysis and to provide details of cold front propagation. These modulation experiments showed in LOC plasmas that the electron thermal transport is not purely diffusive, while in SOC the electron thermal transport is more diffusive like. Linear gyrokinetic simulations suggest the turbulence outside r/a = 0.75 changes from TEM dominance in LOC plasmas to ITG mode dominance in SOC plasmas., United States. Dept. of Energy (DoE Contract No DE-FC02-99ER54512), Oak Ridge Institute for Science and Education (DOE Fusion Energy Postdoctoral Research Program)
- Published
- 2015
37. Improved profile fitting and quantification of uncertainty in experimental measurements of impurity transport coefficients using Gaussian process regression
- Author
-
Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Chilenski, Mark Alan, Greenwald, Martin J., Marzouk, Youssef M., Howard, Nathaniel Thomas, White, Anne E., Rice, John E., Walk Jr., John R., Walk, John R., Jr., Marzouk, Youssef M, Walk Jr, John R, Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Chilenski, Mark Alan, Greenwald, Martin J., Marzouk, Youssef M., Howard, Nathaniel Thomas, White, Anne E., Rice, John E., Walk Jr., John R., Walk, John R., Jr., Marzouk, Youssef M, and Walk Jr, John R
- Abstract
The need to fit smooth temperature and density profiles to discrete observations is ubiquitous in plasma physics, but the prevailing techniques for this have many shortcomings that cast doubt on the statistical validity of the results. This issue is amplified in the context of validation of gyrokinetic transport models (Holland et al 2009 Phys. Plasmas 16 052301), where the strong sensitivity of the code outputs to input gradients means that inadequacies in the profile fitting technique can easily lead to an incorrect assessment of the degree of agreement with experimental measurements. In order to rectify the shortcomings of standard approaches to profile fitting, we have applied Gaussian process regression (GPR), a powerful non-parametric regression technique, to analyse an Alcator C-Mod L-mode discharge used for past gyrokinetic validation work (Howard et al 2012 Nucl. Fusion 52 063002). We show that the GPR techniques can reproduce the previous results while delivering more statistically rigorous fits and uncertainty estimates for both the value and the gradient of plasma profiles with an improved level of automation. We also discuss how the use of GPR can allow for dramatic increases in the rate of convergence of uncertainty propagation for any code that takes experimental profiles as inputs. The new GPR techniques for profile fitting and uncertainty propagation are quite useful and general, and we describe the steps to implementation in detail in this paper. These techniques have the potential to substantially improve the quality of uncertainty estimates on profile fits and the rate of convergence of uncertainty propagation, making them of great interest for wider use in fusion experiments and modelling efforts., United States. Dept. of Energy. Office of Fusion Energy Sciences (Award DE-FC02-99ER54512), United States. Dept. of Energy. Office of Science (Contract DE-AC05-06OR23177), United States. Dept. of Energy. Office of Advanced Scientific Computing Research (Award DE-SC0007099)
- Published
- 2015
38. Non-local heat transport in Alcator C-Mod ohmic L-mode plasmas
- Author
-
Gao, Chi, Rice, John E., Sun, H. J., Reinke, Matthew Logan, Howard, Nathaniel Thomas, Mikkelson, D., Hubbard, Amanda E., Chilenski, Mark Alan, Walk Jr, John R., Hughes, Jerry W., Jr., Ennever, Paul Chappell, Porkolab, Miklos, White, Anne E., Sung, Choongki, Delgado-Aparicio, Luis, Baek, Seung Gyou, Rowan, William L., Brookman, M. W., Greenwald, Martin J., Granetz, Robert S., Wolfe, Stephen M., Marmar, Earl S., Alcator C-Mod Team, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Gao, Chi, Rice, John E., Reinke, Matthew Logan, Howard, Nathaniel Thomas, Hubbard, Amanda E., Chilenski, Mark Alan, Walk Jr, John R., Hughes, Jerry W., Jr., Ennever, Paul Chappell, Porkolab, Miklos, White, Anne E., Sung, Choongki, Delgado-Aparicio, Luis, Baek, Seung Gyou, Rowan, William L., Greenwald, Martin J., Granetz, Robert S., Wolfe, Stephen M., and Marmar, Earl S.
- Subjects
Nuclear and High Energy Physics ,Materials science ,Alcator C-Mod ,Physics::Plasma Physics ,Pinch ,Electron temperature ,Plasma ,Electron ,Collisionality ,Atomic physics ,Condensed Matter Physics ,Thermal diffusivity ,Ohmic contact - Abstract
Non-local heat transport experiments were performed in Alcator C-Mod ohmic L-mode plasmas by inducing edge cooling with laser blow-off impurity (CaF2) injection. The non-local effect, a cooling of the edge electron temperature with a rapid rise of the central electron temperature, which contradicts the assumption of 'local' transport, was observed in low collisionality linear ohmic confinement (LOC) regime plasmas. Transport analysis shows this phenomenon can be explained either by a fast drop of the core diffusivity, or the sudden appearance of a heat pinch. In high collisionality saturated ohmic confinement (SOC) regime plasmas, the thermal transport becomes 'local': the central electron temperature drops on the energy confinement time scale in response to the edge cooling. Measurements from a high resolution imaging x-ray spectrometer show that the ion temperature has a similar behaviour as the electron temperature in response to edge cooling, and that the transition density of non-locality correlates with the rotation reversal critical density. This connection may indicate the possible connection between thermal and momentum transport, which is also linked to a transition in turbulence dominance between trapped electron modes (TEMs) and ion temperature gradient (ITG) modes. Experiments with repetitive cold pulses in one discharge were also performed to allow Fourier analysis and to provide details of cold front propagation. These modulation experiments showed in LOC plasmas that the electron thermal transport is not purely diffusive, while in SOC the electron thermal transport is more diffusive like. Linear gyrokinetic simulations suggest the turbulence outside r/a = 0.75 changes from TEM dominance in LOC plasmas to ITG mode dominance in SOC plasmas., United States. Dept. of Energy (DoE Contract No DE-FC02-99ER54512), Oak Ridge Institute for Science and Education (DOE Fusion Energy Postdoctoral Research Program)
- Published
- 2014
39. Effects of Magnetic Shear on Toroidal Rotation in Tokamak Plasmas with Lower Hybrid Current Drive
- Author
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Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Rice, John E., Podpaly, Y. A., Reinke, Matthew Logan, Mumgaard, Robert Thomas, Shiraiwa, Shunichi, Wallace, Gregory Marriner, Gao, Chi, Granetz, Robert S., Hughes, Jerry W., Parker, Ronald R., Bonoli, Paul T., Greenwald, Martin J., Hubbard, Amanda E., Hutchinson, Ian H., Irby, James Henderson, Marmar, Earl S., Wolfe, Stephen M., Scott, S. D., Chouli, B., Fenzi-Bonizec, C., Nave, M. F. F., Diamond, P. H., Delgado-Aparicio, Luis, Eriksson, L.-G., Giroud, C., Kirov, K., Mailloux, J., Hughes Jr, Jerry, Parker, R., Hubbard, Amanda E, Hutchinson, Ian Horner, Wolfe, Stephen M, Podpaly, Yuri, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Rice, John E., Podpaly, Y. A., Reinke, Matthew Logan, Mumgaard, Robert Thomas, Shiraiwa, Shunichi, Wallace, Gregory Marriner, Gao, Chi, Granetz, Robert S., Hughes, Jerry W., Parker, Ronald R., Bonoli, Paul T., Greenwald, Martin J., Hubbard, Amanda E., Hutchinson, Ian H., Irby, James Henderson, Marmar, Earl S., Wolfe, Stephen M., Scott, S. D., Chouli, B., Fenzi-Bonizec, C., Nave, M. F. F., Diamond, P. H., Delgado-Aparicio, Luis, Eriksson, L.-G., Giroud, C., Kirov, K., Mailloux, J., Hughes Jr, Jerry, Parker, R., Hubbard, Amanda E, Hutchinson, Ian Horner, Wolfe, Stephen M, and Podpaly, Yuri
- Abstract
Application of lower hybrid (LH) current drive in tokamak plasmas can induce both co- and countercurrent directed changes in toroidal rotation, depending on the core q profile. For discharges with q[subscript 0] < 1, rotation increments in the countercurrent direction are observed. If the LH-driven current is sufficient to suppress sawteeth and increase q[subscript 0] above unity, the core toroidal rotation change is in the cocurrent direction. This change in sign of the rotation increment is consistent with a change in sign of the residual stress (the divergence of which constitutes an intrinsic torque that drives the flow) through its dependence on magnetic shear., United States. Dept. of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy (Fusion Research Postdoctoral Research Program)
- Published
- 2014
40. X-ray imaging crystal spectroscopy for use in plasma transport research
- Author
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Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian, Reinke, Matthew Logan, Podpaly, Yuri, Hutchinson, Ian H., Rice, John E., Gao, Chi, Greenwald, Martin J., Howard, Nathaniel Thomas, Hubbard, Amanda E., Hughes, Jerry W., White, Anne E., Wolfe, Stephen M., Bitter, M., Delgado-Aparicio, Luis, Hill, K., Pablant, N., Hutchinson, Ian Horner, Hubbard, Amanda E, Hughes Jr, Jerry, Wolfe, Stephen M, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian, Reinke, Matthew Logan, Podpaly, Yuri, Hutchinson, Ian H., Rice, John E., Gao, Chi, Greenwald, Martin J., Howard, Nathaniel Thomas, Hubbard, Amanda E., Hughes, Jerry W., White, Anne E., Wolfe, Stephen M., Bitter, M., Delgado-Aparicio, Luis, Hill, K., Pablant, N., Hutchinson, Ian Horner, Hubbard, Amanda E, Hughes Jr, Jerry, and Wolfe, Stephen M
- Abstract
This research describes advancements in the spectral analysis and error propagation techniques associated with x-ray imaging crystal spectroscopy (XICS) that have enabled this diagnostic to be used to accurately constrain particle, momentum, and heat transport studies in a tokamak for the first time. Dopplertomography techniques have been extended to include propagation of statistical uncertainty due to photon noise, the effect of non-uniform instrumental broadening as well as flux surface variations in impurity density. These methods have been deployed as a suite of modeling and analysis tools, written in interactive data language (IDL) and designed for general use on tokamaks. Its application to the Alcator C-Mod XICS is discussed, along with novel spectral and spatial calibration techniques. Example ion temperature and radial electric field profiles from recent I-mode plasmas are shown, and the impact of poloidally asymmetric impurity density and natural line broadening is discussed in the context of the planned ITER x-ray crystal spectrometer., United States. Dept. of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy (Contract DE-AC02-09CH11466), United States. Dept. of Energy (Fusion Research Postdoctoral Research Program)
- Published
- 2014
41. Poloidal variation of high-Z impurity density due to hydrogen minority ion cyclotron resonance heating on Alcator C-Mod
- Author
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Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Koch Institute for Integrative Cancer Research at MIT, Hutchinson, Ian, Reinke, Matthew Logan, Hutchinson, Ian H., Rice, John E., Howard, Nathaniel Thomas, Bader, Andrew, Wukitch, Stephen James, Lin, Yijun, Pace, David C., Hubbard, Amanda E., Hughes, Jerry W., Podpaly, Yuri, Hutchinson, Ian Horner, Hubbard, Amanda E, Hughes Jr, Jerry, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Koch Institute for Integrative Cancer Research at MIT, Hutchinson, Ian, Reinke, Matthew Logan, Hutchinson, Ian H., Rice, John E., Howard, Nathaniel Thomas, Bader, Andrew, Wukitch, Stephen James, Lin, Yijun, Pace, David C., Hubbard, Amanda E., Hughes, Jerry W., Podpaly, Yuri, Hutchinson, Ian Horner, Hubbard, Amanda E, and Hughes Jr, Jerry
- Abstract
In the Alcator C-Mod tokamak, strong, steady-state variations of molybdenum density within a flux surface are routinely observed in plasmas using hydrogen minority ion cyclotron resonant heating. In/out asymmetries, up to a factor of 2, occur with either inboard or outboard accumulation depending on the major radius of the minority resonance layer. These poloidal variations can be attributed to the impurity's high charge and large mass in the neoclassical parallel force balance. The large mass enhances the centrifugal force, causing outboard accumulation while the high charge enhances ion-impurity friction and makes impurities sensitive to small poloidal variations in the plasma potential. Quantitative comparisons between existing parallel high-Z impurity transport theories and experimental results for r/a < 0.7 show good agreement when the resonance layer is on the high-field side of the tokamak but disagree substantially for low-field side heating. Ion-impurity friction is insufficient to explain the experimental results, and the accumulation of impurity density on the inboard side of flux surface is shown to be driven by a poloidal potential variation due to magnetic trapping of non-thermal, cyclotron heated minority ions. Parallel impurity transport theory is extended to account for cyclotron effects and shown to agree with experimentally measured impurity density asymmetries., United States. Dept. of Energy (Agreement DE-FC02-99ER54512), United States. Dept. of Energy. Office of Fusion Energy Sciences (Postdoctoral Research Program)
- Published
- 2014
42. Closed-Tube Barcoding1.
- Author
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Sirianni, Nicky M., Yuan, Huijun, Rice, John E., Kaufman, Ronit S., Deng, John, Fulton, Chandler, Wangh, Lawrence J., and Steinke, Dirk
- Subjects
BIODIVERSITY ,GENETIC barcoding ,POLYMERASE chain reaction ,SINGLE-stranded DNA ,TECHNOLOGY - Abstract
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- Published
- 2016
- Full Text
- View/download PDF
43. Transport and turbulence studies in the linear ohmic confinement regime in Alcator C-Mod
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Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Ennever, Paul Chappell, Fiore, Catherine L., Greenwald, Martin J., Hubbard, Amanda E., Dorris, James R., Ma, Y., Marmar, Earl S., Podpaly, Y., Reinke, Matthew Logan, Rice, John E., Rost, Jon C., Tsujii, Naoto, Ernst, Darin R., Candy, J., Staebler, G. M., Waltz, R. E., Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Ennever, Paul Chappell, Fiore, Catherine L., Greenwald, Martin J., Hubbard, Amanda E., Dorris, James R., Ma, Y., Marmar, Earl S., Podpaly, Y., Reinke, Matthew Logan, Rice, John E., Rost, Jon C., Tsujii, Naoto, Ernst, Darin R., Candy, J., Staebler, G. M., and Waltz, R. E.
- Abstract
Transport in ohmically heated plasmas in Alcator C-Mod was studied in both the linear (LOC) and saturated (SOC) ohmic L-mode confinement regimes and the importance of turbulent transport in the region r/a = 0.5–0.8 was established. After an extensive analysis with TGLF and GYRO, it is found that using an effective impurity ion species with Z[subscript i] = 8, and moderately high Z[subscript eff] (2.0–5.6), in the LOC regime electron transport becomes dominant due to TEM turbulence. The key ingredient in the present results is the observation that dilution of the main ion species (deuterium) by impurity species of moderate charge state reduces dominant ITG turbulence, in contrast to the SOC regime with little, if any dilution. The turbulent spectrum measured with the phase contrast imaging (PCI) diagnostic is in qualitative agreement with predictions of a synthetic PCI diagnostic adopted to Global GYRO. The toroidal rotation in the low-density LOC regime is in the co-current direction but as the density is raised in the SOC regime the rotation reverses to the counter current drive direction. The impurity content of the plasma was measured recently and an effective Z[subscript i] of 9 was deduced., United States. Dept. of Energy (Grant DE-FC02-99ER54512-CMOD)
- Published
- 2013
44. Ohmic energy confinement saturation and core toroidal rotation reversal in Alcator C-Mod plasmas
- Author
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Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Rice, John E., Greenwald, Martin J., Podpaly, Y. A., Reinke, Matthew Logan, Hughes, Jerry W., Howard, Nathaniel Thomas, Ma, Y., Cziegler, Istvan, Ennever, Paul Chappell, Ernst, Darin R., Fiore, Catherine L., Gao, Chi, Irby, James Henderson, Marmar, Earl S., Tsujii, Naoto, Wolfe, Stephen M., Diamond, P. H., Duval, B. P., Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Rice, John E., Greenwald, Martin J., Podpaly, Y. A., Reinke, Matthew Logan, Hughes, Jerry W., Howard, Nathaniel Thomas, Ma, Y., Cziegler, Istvan, Ennever, Paul Chappell, Ernst, Darin R., Fiore, Catherine L., Gao, Chi, Irby, James Henderson, Marmar, Earl S., Tsujii, Naoto, Wolfe, Stephen M., Diamond, P. H., and Duval, B. P.
- Abstract
Ohmic energy confinement saturation is found to be closely related to core toroidal rotation reversals in Alcator C-Mod tokamak plasmas. Rotation reversals occur at a critical density, depending on the plasma current and toroidal magnetic field, which coincides with the density separating the linear Ohmic confinement regime from the saturated Ohmic confinement regime. The rotation is directed co-current at low density and abruptly changes direction to counter-current when the energy confinement saturates as the density is increased. Since there is a bifurcation in the direction of the rotation at this critical density, toroidal rotation reversal is a very sensitive indicator in the determination of the regime change. The reversal and confinement saturation results can be unified, since these processes occur in a particular range of the collisionality., United States. Dept. of Energy (Contract DE-FC02-99ER54512)
- Published
- 2013
45. Formation and Stability of Impurity “Snakes” in Tokamak Plasmas
- Author
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Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Laboratory for Nuclear Science, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Delgado-Aparicio, Luis, Sugiyama, Linda E., Granetz, Robert S., Rice, John E., Reinke, Matthew Logan, Gao, Chi, Greenwald, Martin J., Hubbard, Amanda E., Hughes, Jerry W., Marmar, Earl S., Podpaly, Y., Wolfe, S., Wukitch, Stephen James, Gates, D. A., Bitter, M., Fredrickson, E., Hill, K., Pablant, N., Scott, S., Wilson, R., Gao, Chi, Ph. D. Massachusetts Institute of Technology, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Laboratory for Nuclear Science, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Delgado-Aparicio, Luis, Sugiyama, Linda E., Granetz, Robert S., Rice, John E., Reinke, Matthew Logan, Gao, Chi, Greenwald, Martin J., Hubbard, Amanda E., Hughes, Jerry W., Marmar, Earl S., Podpaly, Y., Wolfe, S., Wukitch, Stephen James, Gates, D. A., Bitter, M., Fredrickson, E., Hill, K., Pablant, N., Scott, S., Wilson, R., and Gao, Chi, Ph. D. Massachusetts Institute of Technology
- Abstract
New observations of the formation and dynamics of long-lived impurity-induced helical “snake” modes in tokamak plasmas have recently been carried out on Alcator C-Mod. The snakes form as an asymmetry in the impurity ion density that undergoes a seamless transition from a small helically displaced density to a large crescent-shaped helical structure inside q<1, with a regularly sawtoothing core. The observations show that the conditions for the formation and persistence of a snake cannot be explained by plasma pressure alone. Instead, many features arise naturally from nonlinear interactions in a 3D MHD model that separately evolves the plasma density and temperature., United States. Dept. of Energy (Contract DE-FC02-99ER54512)
- Published
- 2013
46. Rotation Reversal Bifurcation and Energy Confinement Saturation in Tokamak Ohmic L-Mode Plasmas
- Author
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Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Driscoll, John E., Cziegler, Istvan, Diamond, P. H., Duval, B. P., Podpaly, Yuri A., Reinke, Matthew Logan, Ennever, Paul Chappell, Greenwald, Martin J., Hughes, Jerry W., Ma, Y., Marmar, Earl S., Tsujii, Naoto, Wolfe, Stephen M., Rice, John E., Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Driscoll, John E., Cziegler, Istvan, Diamond, P. H., Duval, B. P., Podpaly, Yuri A., Reinke, Matthew Logan, Ennever, Paul Chappell, Greenwald, Martin J., Hughes, Jerry W., Ma, Y., Marmar, Earl S., Tsujii, Naoto, Wolfe, Stephen M., and Rice, John E.
- Abstract
Direction reversals of intrinsic toroidal rotation have been observed in diverted Alcator C-Mod Ohmic L-mode plasmas following electron density ramps. For low density discharges, the core rotation is directed cocurrent, and reverses to countercurrent following an increase in the density above a certain threshold. Such reversals occur together with a decrease in density fluctuations with 2 cm[superscript -1]≤k[subscript θ]≤11 cm[superscript -1] and frequencies above 70 kHz. There is a strong correlation between the reversal density and the density at which the Ohmic L-mode energy confinement changes from the linear to the saturated regime., United States. Dept. of Energy (Contract No. DE-FC02-99ER54512)
- Published
- 2012
47. Edge energy transport barrier and turbulence in the I-mode regime on Alcator C-Mod
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Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis G., Hubbard, Amanda E., Churchill, Randy Michael, Cziegler, Istvan, Dominguez, A., Golfinopoulos, Theodore, Hughes, Jerry W., Rice, John E., Greenwald, Martin J., Howard, Nathaniel Thomas, Lipschultz, Bruce, Marmar, Earl S., Reinke, Matthew Logan, Terry, James L., Bespamyatnov, I., Rowan, W. L., Alcator C-Mod Group, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis G., Hubbard, Amanda E., Churchill, Randy Michael, Cziegler, Istvan, Dominguez, A., Golfinopoulos, Theodore, Hughes, Jerry W., Rice, John E., Greenwald, Martin J., Howard, Nathaniel Thomas, Lipschultz, Bruce, Marmar, Earl S., Reinke, Matthew Logan, Terry, James L., Bespamyatnov, I., Rowan, W. L., and Alcator C-Mod Group
- Abstract
We report extended studies of the I-mode regime [Whyte et al., Nucl. Fusion 50, 105005 (2010)] obtained in the Alcator C-Mod tokamak [Marmar et al., Fusion Sci. Technol. 51(3), 3261 (2007)]. This regime, usually accessed with unfavorable ion B × ∇B drift, features an edge thermal transport barrier without a strong particle transport barrier. Steady I-modes have now been obtained with favorable B × ∇B drift, by using specific plasma shapes, as well as with unfavorable drift over a wider range of shapes and plasma parameters. With favorable drift, power thresholds are close to the standard scaling for L–H transitions, while with unfavorable drift they are ∼ 1.5–3 times higher, increasing with Ip. Global energy confinement in both drift configurations is comparable to H-mode scalings, while density profiles and impurity confinement are close to those in L-mode. Transport analysis of the edge region shows a decrease in edge χeff, by typically a factor of 3, between L- and I-mode. The decrease correlates with a drop in mid-frequency fluctuations (f ∼ 50–150 kHz) observed on both density and magnetics diagnostics. Edge fluctuations at higher frequencies often increase above L-mode levels, peaking at f ∼ 250 kHz. This weakly coherent mode is clearest and has narrowest width (Δf/f ∼ 0.45) at low q95 and high Tped, up to 1 keV. The Er well in I-mode is intermediate between L- and H-mode and is dominated by the diamagnetic contribution in the impurity radial force balance, without the Vpol shear typical of H-modes., United States. Dept. of Energy (Contract No. DE-FG03-96ER54373), United States. Dept. of Energy (Contract No. DEFC02- 99ER54512)
- Published
- 2011
48. Modification of current profile, toroidal rotation and pedestal by lower hybrid waves in Alcator C-Mod
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Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Parker, R., Bonoli, Paul T., Meneghini, Orso-Maria Cornelio, Schmidt, Andrea Elizabeth, Shiraiwa, Shunichi, Wallace, Gregory Marriner, Hubbard, Amanda E., Hughes, Jerry W., Ko, J. S., McDermott, R. M., Reinke, Matthew Logan, Rice, John E., Wilson, J. R., Scott, S., Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Parker, R., Bonoli, Paul T., Meneghini, Orso-Maria Cornelio, Schmidt, Andrea Elizabeth, Shiraiwa, Shunichi, Wallace, Gregory Marriner, Hubbard, Amanda E., Hughes, Jerry W., Ko, J. S., McDermott, R. M., Reinke, Matthew Logan, Rice, John E., Wilson, J. R., and Scott, S.
- Abstract
Recent results from the lower hybrid current drive experiments on Alcator C-Mod are presented. These include i) MSE measurements of broadened LHCD current profiles; ii) development of counter rotation comparable to the rate of injected wave momentum; iii) modification of pedestals and rotation in H-mode; and iv) development of a new FEM-based code that models LH wave propagation from the RF source to absorption in the plasma. An improved antenna concept that will be used in the upcoming C-Mod campaigns is also briefly described., United States. Dept. of Energy (grant DE-FC02- 99ER54512), United States. Dept. of Energy (grant DE-AC02-76CH03073)
- Published
- 2011
49. Edge Temperature Gradient as Intrinsic Rotation Drive in Alcator C-Mod Tokamak Plasmas
- Author
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Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis G., Rice, John E., Hughes, Jerry W., Podpaly, Yuri A., Reinke, Matthew Logan, Greenwald, Martin J., Hubbard, Amanda E., Marmar, Earl S., Diamond, P. H., Kosuga, Y., Gürcan, Ö. D., Hahm, T. S., McDevitt, C. J., Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis G., Rice, John E., Hughes, Jerry W., Podpaly, Yuri A., Reinke, Matthew Logan, Greenwald, Martin J., Hubbard, Amanda E., Marmar, Earl S., Diamond, P. H., Kosuga, Y., Gürcan, Ö. D., Hahm, T. S., and McDevitt, C. J.
- Abstract
Intrinsic rotation has been observed in I-mode plasmas from the C-Mod tokamak, and is found to be similar to that in H mode, both in its edge origin and in the scaling with global pressure. Since both plasmas have similar edge ∇T, but completely different edge ∇n, it may be concluded that the drive of the intrinsic rotation is the edge ∇T rather than ∇P. Evidence suggests that the connection between gradients and rotation is the residual stress, and a scaling for the rotation from conversion of free energy to macroscopic flow is calculated., United States. Dept. of Energy (contract DE-FC02-99ER54512), United States. Dept. of Energy (contract DEAC02- 09CH11466), United States. Dept. of Energy (contract DE-FG02-04ER54738), Korea (South). Ministry of Education, Science and Technology (MEST) (W. C. I. program), French National Research Agency (ANR) (contract ANR-06-PLAN-0084)
- Published
- 2011
50. ICRF Mode Conversion Flow Drive on Alcator C-Mod and Projections to Other Tokamaks
- Author
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Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Lin, Yijun, Rice, John E., Wukitch, Stephen James, Greenwald, Martin J., Hubbard, Amanda E., Ince-Cushman, Alexander, Lin, Liang, Marmar, Earl S., Reinke, Matthew Logan, Tsujii, Naoto, Wright, John C., Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Lin, Yijun, Rice, John E., Wukitch, Stephen James, Greenwald, Martin J., Hubbard, Amanda E., Ince-Cushman, Alexander, Lin, Liang, Marmar, Earl S., Reinke, Matthew Logan, Tsujii, Naoto, and Wright, John C.
- Abstract
Plasma flow drive via ICRF mode conversion (MC) has been demonstrated on Alcator C-Mod. The toroidal rotation in these D([superscript 3]He) MC plasmas is typically more than twice above the empirically determined intrinsic rotation scaling in ICRF minority heated plasmas. In L-mode plasmas at 3 MW ICRF power input, up to 90 km/s toroidal rotation and 2 km/s localized ( r/a~0.4) poloidal rotation has been observed. The MC ion cyclotron wave (ICW) was detected by a phase contrast imaging system in heterodyne setup. Through TORIC 2-D full wave simulation, and comparison with other experimental evidence, we hypothesize that the interaction between the MC ICW and the [superscript 3]He ions may be the mechanism for the observed MC flow drive. TORIC simulation suggests that similar flow drive scenario may be realized on JET D(3He) plasmas. The promising scenarios on ITER are the inverted minority scenario (T)D and high field launch for T-D-([superscript 3]He) plasma. In non-radioactive phase, these correspond to ([superscript 3]He)-H and [superscript 4]He([superscript 3]He) plasmas respectively., United States. Dept. of Energy (grant DE-FC02-99-ER54512)
- Published
- 2011
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