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1. The separatrix operational space of next-step fusion experiments: From ASDEX Upgrade data to SPARC scenarios

Author

Eich, Thomas, Body, Thomas, Faitsch, Michael, Grover, Ondrej, Miller, Marco Andres, Manz, Peter, Looby, Tom, Kuang, Adam Qingyang, Redl, Andreas, Reinke, Matt, Creely, Alex J., Battaglia, Devon, Hillesheim, Jon, Wigram, Mike, Hughes, Jerry W., and team, the ASDEX Upgrade

Subjects
Physics - Plasma Physics
Abstract

Fusion power plants require ELM-free, detached operation to prevent divertor damage and erosion. The separatrix operational space (SepOS) is proposed as a tool for identifying access to the type-I ELM-free quasi-continuous exhaust regime. In this work, we recast the SepOS framework using simple parameters and present dedicated ASDEX Upgrade discharges to demonstrate how to interpret its results. Analyzing an extended ASDEX Upgrade database consisting of 6688 individual measurements, we show that SepOS accurately describes how the H-mode boundary varies with plasma current and magnetic field strength. We then introduce a normalized SepOS framework and LH minimum scaling and show that normalized boundaries across multiple machines are nearly identical, suggesting that the normalized SepOS can be used to translate results between different machines. The LH minimum density predicted by SepOS is found to closely match an experimentally determined multi-machine scaling, which provides a further indirect validation of SepOS across multiple devices. Finally, we demonstrate how SepOS can be used predictively, identifying a viable QCE operational point for SPARC, at a separatrix density of 4e20/m3, a separatrix temperature of 156eV and an alpha-t of 0.7 - a value solidly within the QCE operational space on ASDEX Upgrade. This demonstrates how SepOS provides a concise, intuitive method for scoping ELM-free operation on next-step devices., Comment: Conference paper for PSI-26 (Plasma Surface Interactions)

Published
2024

6. Effect of opacity on the density pedestal structure in DIII-D and Alcator C-Mod

Author

Mordijck, S., Groebner, Richard Joseph, Osborne, Tom, Carlstrom, Thomas Neil, Glass, Fenton, Snyder, Philip B., Hughes, Jerry W., Järvinen, Aaro E., Salmi, Antti, Tala, Tuomas, Laggner, Florian, McKee, George R., Moyer, Richard A., Rhodes, Terry L., and Zeng, Lei

Abstract

Analysis of experimental data from DIII-D and C-Mod is used to study the role of opacity on the density pedestal structure. Dα measurements at the midplane on DIII-D indicate that we were able to push the ionization front further out by increasing the separatrix and SOL electron densities. We find that in pressure-record breaking EDA H-modes on C-Mod, adding more gas fueling does not result in an increase of the pedestal density, only an increase in the SOL density. In DIII-D, using gas puff modulations, we observe that when the outer strike point detaches, this strongly reduces the amplitude of the electron density response in the SOL and results in a larger amplitude inside the separatrix. Moreover, we observe the creation of an up-down asymmetry in the electron density with increased gas puff/opacity. Close to the X-point, up to ψN ~ 0.98, the electron density is larger than upstream in DIII-D. SOLPS modeling will be performed to get a better evaluation of the poloidal and radial ionization profiles as well as to better understand the origin of the up-down asymmetry of the electron density in DIII-D.

Published
2018

8. Particle Transport From the Bottom Up

Author

Mordijck, S., Zeng, L., Rhodes, Terry L., Schmitz, L., Hughes, Jerry W., Tala, Tuomas, Salmi, Antti, Baranov, Y., Petty, C.C., Groebner, Richard Joseph, and Moser, A.L.

Published
2018

9. Density profile peaking on DIII-D and JET – fuelling versus transport

Author

Salmi, Antti, Tala, Tuomas, Mordijck, S., Nordman, Hans, and Hughes, Jerry W.

Subjects
Physics::Plasma Physics
Abstract

Dimensionless collisionality (ν*) scans with fixed density in H-mode plasmas on DIII-D and JET together with modelling have shown that the NBI fuelling plays a more important role in density peaking than found in earlier multi-machine datasets where the increased peaking at low collisionality has been primarily ascribed to turbulent effects. Perturbative gas puff modulations are performed to disentangle the fuelling and the transport effects. On DIII-D, we find that, at the lowest ν*, the pinch is directed outward and the diffusion coefficients are larger compared to higher ν* cases. With increasing ν*, the pinch becomes inward outside the mid-radius, while remaining outward inside the mid-radius. At the same time, a strong increase in ion-scale density fluctuations with reduced ν* is observed with BES and predicted with TGLF. On JET, perturbative transport analysis, predictive integrated modelling with JINTRAC+TGLF and non-linear and linear GENE runs all show that NBI fuelling provides an important contribution to density peaking. These results indicate that the density profiles on ITER, where NBI fuelling is very small, may be less peaked than previously thought.

Published
2018

10. Non-local heat transport in Alcator C-Mod ohmic L-mode plasmas

Author

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

11. Constraining the divertor heat width in ITER

Author

Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis G., Labombard, Brian, Hughes, Jerry W., Jr., Lipschultz, Bruce, Terry, James L., Brunner, Daniel Frederic, Stangeby, P. C., Elder, D., Leonard, A. W., Watkins, J., Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis G., Labombard, Brian, Hughes, Jerry W., Jr., Lipschultz, Bruce, Terry, James L., Brunner, Daniel Frederic, Stangeby, P. C., Elder, D., Leonard, A. W., and Watkins, J.

Abstract

United States. Department of Defense (US DOE award DE-SC00-02060), United States. Department of Defense (contract DE-FC02-99ER54512), United States. Department of Defense (cooperative agreement DE-FC02- 04ER54698)

Published
2016

12. 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
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13. Heat-flux footprints for I-mode and EDA H-mode plasmas on Alcator C-Mod

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Terry, James L., Labombard, Brian, Brunner, Daniel Frederic, Hughes, Jerry W., Jr., Reinke, Matthew Logan, Whyte, Dennis G., Terry, James L, Hughes Jr, Jerry, Whyte, Dennis G, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Terry, James L., Labombard, Brian, Brunner, Daniel Frederic, Hughes, Jerry W., Jr., Reinke, Matthew Logan, Whyte, Dennis G., Terry, James L, Hughes Jr, Jerry, and Whyte, Dennis G

Abstract

United States. Dept. of Energy (Cooperative Agreement DE-FC02-99-ER54512)

Published
2015

14. Correlation ECE diagnostic in Alcator C-Mod

Author

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, Sung, Choongki, White, Anne E., Howard, Nathaniel Thomas, Irby, James Henderson, Leccacorvi, Rick, Vieira, Rui F., Oi, Curran, Rice, John E., Reinke, Matthew Logan, Gao, Chi, Ennever, Paul Chappell, Porkolab, Miklos, Churchill, Randy, Theiler, Christian, Walk, John R., Jr., Hughes, Jerry W., Jr., Hubbard, Amanda E., Greenwald, Martin J., Mikkelsen, David, Walk Jr, John R, Hughes Jr, Jerry, Hubbard, Amanda E, Vieira, Rui F, 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, Sung, Choongki, White, Anne E., Howard, Nathaniel Thomas, Irby, James Henderson, Leccacorvi, Rick, Vieira, Rui F., Oi, Curran, Rice, John E., Reinke, Matthew Logan, Gao, Chi, Ennever, Paul Chappell, Porkolab, Miklos, Churchill, Randy, Theiler, Christian, Walk, John R., Jr., Hughes, Jerry W., Jr., Hubbard, Amanda E., Greenwald, Martin J., Mikkelsen, David, Walk Jr, John R, Hughes Jr, Jerry, Hubbard, Amanda E, and Vieira, Rui F

Published
2015

15. 20 years of research on the Alcator C-Mod tokamak

Author

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, Greenwald, Martin J., Baek, Seung Gyou, Barnard, Harold, Beck, William K., Bonoli, Paul T., Brunner, Daniel Frederic, Burke, William M., Ennever, Paul Chappell, Ernst, Darin R., Faust, Ian Charles, Fiore, Catherine, Fredian, Thomas W., Gao, Chi, Golfinopoulos, Theodore, Granetz, Robert S., Hartwig, Zachary, Hubbard, Amanda E., Hughes, Jerry W., Jr., Hutchinson, Ian H., Irby, James Henderson, Labombard, Brian, Li, Chikang, Lin, Yijun, Marmar, Earl S., Mumgaard, Robert Thomas, Parker, Ronald R., Porkolab, Miklos, Rice, John E., Shiraiwa, Shunichi, Sierchio, Jennifer M., Sorbom, Brandon Nils, Stillerman, Joshua A., Sung, Choongki, Terry, David Rankin, Terry, James L., Vieira, Rui F., Walk, John R., Jr., Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G., Wolfe, Stephen M., Wright, Graham, Wright, John C., Wukitch, Stephen James, Barnard, Harold Salvadore, Hartwig, Zachary Seth, Hubbard, Amanda E, Hughes Jr, Jerry, Hutchinson, Ian Horner, Parker, R., Terry, James L, Vieira, Rui F, Walk Jr, John R, Whyte, Dennis G, Wolfe, Stephen M, 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, Greenwald, Martin J., Baek, Seung Gyou, Barnard, Harold, Beck, William K., Bonoli, Paul T., Brunner, Daniel Frederic, Burke, William M., Ennever, Paul Chappell, Ernst, Darin R., Faust, Ian Charles, Fiore, Catherine, Fredian, Thomas W., Gao, Chi, Golfinopoulos, Theodore, Granetz, Robert S., Hartwig, Zachary, Hubbard, Amanda E., Hughes, Jerry W., Jr., Hutchinson, Ian H., Irby, James Henderson, Labombard, Brian, Li, Chikang, Lin, Yijun, Marmar, Earl S., Mumgaard, Robert Thomas, Parker, Ronald R., Porkolab, Miklos, Rice, John E., Shiraiwa, Shunichi, Sierchio, Jennifer M., Sorbom, Brandon Nils, Stillerman, Joshua A., Sung, Choongki, Terry, David Rankin, Terry, James L., Vieira, Rui F., Walk, John R., Jr., Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G., Wolfe, Stephen M., Wright, Graham, Wright, John C., Wukitch, Stephen James, Barnard, Harold Salvadore, Hartwig, Zachary Seth, Hubbard, Amanda E, Hughes Jr, Jerry, Hutchinson, Ian Horner, Parker, R., Terry, James L, Vieira, Rui F, Walk Jr, John R, Whyte, Dennis G, and Wolfe, Stephen M

Abstract

United States. Dept. of Energy (Cooperative Agreement DE-FC02-99ER54512), United States. Dept. of Energy (Cooperative Agreement DE-FG03-94ER-54241), United States. Dept. of Energy (Cooperative Agreement DE-AC02-78ET- 51013), United States. Dept. of Energy (Cooperative Agreement DE-AC02-09CH11466), United States. Dept. of Energy (Cooperative Agreement DE-FG02-95ER54309), United States. Dept. of Energy (Cooperative Agreement DE-AC02-05CH11231), United States. Dept. of Energy (Cooperative Agreement DE-AC52-07NA27344), United States. Dept. of Energy (Cooperative Agreement DE-FG02- 97ER54392), United States. Dept. of Energy (Cooperative Agreement DE-SC00-02060)

Published
2015

16. Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature

Author

Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Theiler, Christian, Churchill, Randy Michael, Lipschultz, Bruce, Ernst, Darin R., Hughes, Jerry W., Jr., Catto, Peter J., Reinke, Matthew Logan, Hubbard, Amanda E., Marmar, Earl S., Terry, J. T., Walk, John R., Landreman, Matthew Joseph, Parra, F.I., Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Theiler, Christian, Churchill, Randy Michael, Lipschultz, Bruce, Ernst, Darin R., Hughes, Jerry W., Jr., Catto, Peter J., Reinke, Matthew Logan, Hubbard, Amanda E., Marmar, Earl S., Terry, J. T., Walk, John R., Landreman, Matthew Joseph, and Parra, F.I.

Abstract

We present inboard (HFS) and outboard (LFS) radial electric field (E[subscript r]) and impurity temperature (T[subscript z]) measurements in the I-mode and H-mode pedestal of Alcator C-Mod. These measurements reveal strong Er wells at the HFS and the LFS midplane in both regimes and clear pedestals in T[subscript z], which are of similar shape and height for the HFS and LFS. While the H-mode E[subscript r] well has a radially symmetric structure, the E[subscript r] well in I-mode is asymmetric, with a stronger ExB shear layer at the outer edge of the E[subscript r] well, near the separatrix. Comparison of HFS and LFS profiles indicates that impurity temperature and plasma potential are not simultaneously flux functions. Uncertainties in radial alignment after mapping HFS measurements along flux surfaces to the LFS do not, however, allow direct determination as to which quantity varies poloidally and to what extent. Radially aligning HFS and LFS measurements based on the T[subscript z] profiles would result in substantial inboard-outboard variations of plasma potential and electron density. Aligning HFS and LFS E[subscript r] wells instead also approximately aligns the impurity poloidal flow profiles, while resulting in a LFS impurity temperature exceeding the HFS values in the region of steepest gradients by up to 70%. Considerations based on a simplified form of total parallel momentum balance and estimates of parallel and perpendicular heat transport time scales seem to favor an approximate alignment of the E[subscript r] wells and a substantial poloidal asymmetry in impurity temperature., United States. Dept. of Energy (Cooperative Agreement DE-FC02-99ER54512), Swiss National Science Foundation

Published
2015

17. Non-neoclassical up/down asymmetry of impurity emission on Alcator C-Mod

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian, Reinke, Matthew Logan, Rice, John E., Hutchinson, Ian H., Greenwald, Martin J., Howard, Nathaniel Thomas, Hughes, Jerry W., Irby, James Henderson, Podpaly, Yuri, Terry, James L., White, Anne E., Hutchinson, Ian Horner, Hughes Jr, Jerry, Terry, James L, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian, Reinke, Matthew Logan, Rice, John E., Hutchinson, Ian H., Greenwald, Martin J., Howard, Nathaniel Thomas, Hughes, Jerry W., Irby, James Henderson, Podpaly, Yuri, Terry, James L., White, Anne E., Hutchinson, Ian Horner, Hughes Jr, Jerry, and Terry, James L

Abstract

United States. Dept. of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy (Fusion Research Postdoctoral Research Program)

Published
2014

18. Parallel transport studies of high-Z impurities in the core of Alcator C-Mod plasmas

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian, Reinke, Matthew Logan, Hutchinson, Ian H., Rice, John E., Greenwald, Martin J., Howard, Nathaniel Thomas, Hubbard, Amanda E., Hughes, Jerry W., Terry, James L., Wolfe, Stephen M., Hutchinson, Ian Horner, Hubbard, Amanda E, Hughes Jr, Jerry, Terry, James L, 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, Hutchinson, Ian H., Rice, John E., Greenwald, Martin J., Howard, Nathaniel Thomas, Hubbard, Amanda E., Hughes, Jerry W., Terry, James L., Wolfe, Stephen M., Hutchinson, Ian Horner, Hubbard, Amanda E, Hughes Jr, Jerry, Terry, James L, and Wolfe, Stephen M

Abstract

United States. Dept. of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy (Fusion Research Postdoctoral Research Program)

Published
2014

19. A device for tritium enrichment of glow discharge polymer inertial confinement fusion targets

Author

Ronald G. Ballinger., Massachusetts Institute of Technology. Department of Nuclear Engineering., Hughes, Jerry W. (Jerry Wayne), 1975, Ronald G. Ballinger., Massachusetts Institute of Technology. Department of Nuclear Engineering., and Hughes, Jerry W. (Jerry Wayne), 1975

Abstract

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999., Includes bibliographical references (p. 79-81)., by Jerry W. Hughes, Jr., S.M.

Published
2014

20. Effects of Magnetic Shear on Toroidal Rotation in Tokamak Plasmas with Lower Hybrid Current Drive

Author

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

21. X-ray imaging crystal spectroscopy for use in plasma transport research

Author

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

22. Poloidal variation of high-Z impurity density due to hydrogen minority ion cyclotron resonance heating on Alcator C-Mod

Author

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

23. Observation of Edge Instability Limiting the Pedestal Growth in Tokamak Plasmas

Author

Massachusetts Institute of Technology. Plasma Science and Fusion Center, Greenwald, Martin J., Labombard, Brian, Davis, E., Baek, Seung Gyou, Hughes, Jerry W., Jr., Theiler, C., Walk, J., Golfinopoulos, Theodore, Terry, James L., Churchill, M., Hubbard, Amanda E., Porkolab, Miklos, Reinke, Matthew Logan, White, A., Diallo, A., Snyder, P., Canik, J., Delgado-Aparicio, Luis, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Greenwald, Martin J., Labombard, Brian, Davis, E., Baek, Seung Gyou, Hughes, Jerry W., Jr., Theiler, C., Walk, J., Golfinopoulos, Theodore, Terry, James L., Churchill, M., Hubbard, Amanda E., Porkolab, Miklos, Reinke, Matthew Logan, White, A., Diallo, A., Snyder, P., Canik, J., and Delgado-Aparicio, Luis

Abstract

With fusion device performance hinging on the edge pedestal pressure, it is imperative to experimentally understand the physical mechanism dictating the pedestal characteristics and to validate and improve pedestal predictive models. This Letter reports direct evidence of density and magnetic fluctuations showing the stiff onset of an edge instability leading to the saturation of the pedestal on the Alcator C-Mod tokamak. Edge stability analyses indicate that the pedestal is unstable to both ballooning mode and kinetic ballooning mode in agreement with observations., United States. Dept. of Energy (Contract DE-FC02-99ER54512), Oak Ridge Institute for Science and Education (United States. Dept. of Energy. Office of Fusion Energy Sciences Postdoctoral Research Program)

Published
2014

24. Lower hybrid current drive at high density in the multi-pass regime

Author

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. Plasma Science and Fusion Center, Wallace, Gregory Marriner, Faust, Ian Charles, Meneghini, Orso-Maria Cornelio, Parker, Ronald R., Shiraiwa, Shunichi, Baek, Seung Gyou, Bonoli, Paul T., Hubbard, Amanda E., Hughes, Jerry W., Labombard, Brian, Lau, C., Ma, Y., Reinke, Matthew Logan, Terry, James L., Whyte, Dennis G., Wright, John C., Wukitch, Stephen James, Schmidt, A. E., Harvey, R. W., Smirnov, A. P., Wilson, J. R., 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. Plasma Science and Fusion Center, Wallace, Gregory Marriner, Faust, Ian Charles, Meneghini, Orso-Maria Cornelio, Parker, Ronald R., Shiraiwa, Shunichi, Baek, Seung Gyou, Bonoli, Paul T., Hubbard, Amanda E., Hughes, Jerry W., Labombard, Brian, Lau, C., Ma, Y., Reinke, Matthew Logan, Terry, James L., Whyte, Dennis G., Wright, John C., Wukitch, Stephen James, Schmidt, A. E., Harvey, R. W., Smirnov, A. P., and Wilson, J. R.

Abstract

United States. Dept. of Energy (Award DE-FC02-99ER54512), United States. Dept. of Energy (Award DE-AC02-09CH11466)

Published
2013

25. Non-local heat transport, rotation reversals and up/down impurity density asymmetries in Alcator C-Mod ohmic L-mode plasmas

Author

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., Gao, Chi, Reinke, Matthew Logan, Howard, Nathaniel Thomas, Hubbard, Amanda E., Podpaly, Y.A., Terry, James L., Chilenski, Mark Alan, Ennever, Paul Chappell, Ernst, Darin R., Greenwald, Martin J., Hughes, Jerry W., Ma, Y., Marmar, Earl S., Porkolab, Miklos, White, Anne E., Wolfe, Stephen M., Diamond, P. H., Sun, H. J., Cziegler, Istvan, Podpaly, Y. A., Rowan, W. L., Delgado-Aparicio, Luis, Marmar, E. S., Gao, Chi, Ph. D. Massachusetts Institute of Technology, 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., Gao, Chi, Reinke, Matthew Logan, Howard, Nathaniel Thomas, Hubbard, Amanda E., Podpaly, Y.A., Terry, James L., Chilenski, Mark Alan, Ennever, Paul Chappell, Ernst, Darin R., Greenwald, Martin J., Hughes, Jerry W., Ma, Y., Marmar, Earl S., Porkolab, Miklos, White, Anne E., Wolfe, Stephen M., Diamond, P. H., Sun, H. J., Cziegler, Istvan, Podpaly, Y. A., Rowan, W. L., Delgado-Aparicio, Luis, Marmar, E. S., and Gao, Chi, Ph. D. Massachusetts Institute of Technology

Abstract

United States. Dept. of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy. Office of Fusion Energy Sciences (Postdoctoral Research Program)

Published
2013

26. Density sensitivity of intrinsic rotation profiles in ion cyclotron range of frequency-heated L-mode plasmas

Author

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, Reinke, Matthew Logan, Rice, John E., White, Anne E., Greenwald, Martin J., Howard, Nathaniel Thomas, Ennever, Paul Chappell, Hubbard, Amanda E., Hughes, Jerry W., Gao, Chi, Hubbard, Amanda E, Hughes Jr, Jerry, 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, Reinke, Matthew Logan, Rice, John E., White, Anne E., Greenwald, Martin J., Howard, Nathaniel Thomas, Ennever, Paul Chappell, Hubbard, Amanda E., Hughes, Jerry W., Gao, Chi, Hubbard, Amanda E, and Hughes Jr, Jerry

Abstract

United States. Dept. of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy. Office of Fusion Energy Sciences (Postdoctoral Research Program)

Published
2013

27. Investigation of the Thomson scattering-ECE discrepancy in ICRF heated plasmas at Alcator C-Mod

Author

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, White, Anne E., Hubbard, Amanda E., Hughes, Jerry W., Bonoli, Paul T., Bader, Andrew, Lin, Yijun, Ma, Y., Wolfe, Stephen M., Wukitch, Stephen James, Austin, M. E., Harvey, R. W., Reinke, M. L., Wolfe, Stephen M, Ma, Yunxing, 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, White, Anne E., Hubbard, Amanda E., Hughes, Jerry W., Bonoli, Paul T., Bader, Andrew, Lin, Yijun, Ma, Y., Wolfe, Stephen M., Wukitch, Stephen James, Austin, M. E., Harvey, R. W., Reinke, M. L., Wolfe, Stephen M, Ma, Yunxing, Hubbard, Amanda E, and Hughes Jr, Jerry

Abstract

This paper reports on new experiments at Alcator C-Mod that were performed in order to investigate the long-standing, unresolved discrepancy between Thomson scattering (TS) and electron cyclotron emission (ECE) measurements of electron temperature in high temperature tokamak plasmas. Ion cyclotron range of frequency (ICRF) heating is used to produce high temperature conditions where the type of TS-ECE discrepancy observed in the past at JET and TFTR should become observable. At Alcator C-Mod, plasmas with Te(0) up to 8 keV are obtained using ion cyclotron resonance heating (ICRH), ICRF mode conversion heating and a combination of the two heating methods in order to explore the hypothesis that the presence of ICRH-generated fast ions may be related to the discrepancy. In all high temperature cases, the TS and ECE measurements of electron temperature agree to within experimental uncertainties. We find no evidence for the type of discrepancy reported at JET and TFTR. These results show that the TS-ECE discrepancy does not depend on high temperatures alone and also that the presence of ICRH-generated fast ions is insufficient to cause the TS-ECE discrepancy., United States. Dept. of Energy (DE-FC02-99ER54512)

Published
2013

28. Ohmic energy confinement saturation and core toroidal rotation reversal in Alcator C-Mod plasmas

Author

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

29. Formation and Stability of Impurity “Snakes” in Tokamak Plasmas

Author

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

30. Electron temperature fluctuations associated with the weakly coherent mode in the edge of I-mode plasmas

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, White, Anne E., Whyte, Dennis G., Hubbard, Amanda E., Sung, Choongki, Hughes, Jerry W., Dominguez, Arturo, Terry, James L., Cziegler, Istvan, Phillips, P., Whyte, Dennis G, Hubbard, Amanda E, Hughes Jr, Jerry, Terry, James L, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, White, Anne E., Whyte, Dennis G., Hubbard, Amanda E., Sung, Choongki, Hughes, Jerry W., Dominguez, Arturo, Terry, James L., Cziegler, Istvan, Phillips, P., Whyte, Dennis G, Hubbard, Amanda E, Hughes Jr, Jerry, and Terry, James L

Abstract

New measurements of electron temperature fluctuations associated with the weakly coherent mode (WCM) during improved mode, or I-mode plasmas (Whyte et al 2010 Nucl. Fusion. 50 105005) at Alcator C-Mod (Marmar et al 2007 Fusion. Sci. Technol. 51 3261) are presented in this paper. The measurements are made with a 32-channel, high-resolution profile electron cyclotron emission radiometer. The WCM electron temperature fluctuations are localized to a 1 cm region inside the last closed flux surface. The WCM electron temperature fluctuation level is measured in several different I-mode discharges and is in the range 1% [~ over T][subscript e/T[subscript e] < 2%, which is an order of magnitude smaller than the WCM density fluctuation level. The WCM edge fluctuations observed in I-mode are believed to play a role in increasing particle transport but not energy transport in the edge of I-mode plasmas. The large difference between normalized density and electron temperature fluctuation amplitudes provides new evidence that the WCM fluctuations can separately affect energy and particle transport., United States. Dept. of Energy (DE-FC02-99-ER54512-CMOD)

Published
2013

31. Rotation Reversal Bifurcation and Energy Confinement Saturation in Tokamak Ohmic L-Mode Plasmas

Author

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

United States. Dept. of Energy (Contract No. DE-FC02-99ER54512)

Published
2012

32. Edge energy transport barrier and turbulence in the I-mode regime on Alcator C-Mod

Author

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

United States. Dept. of Energy (Contract No. DE-FG03-96ER54373), United States. Dept. of Energy (Contract No. DEFC02- 99ER54512)

Published
2011

33. Scaling of the power exhaust channel in Alcator C-Mod

Author

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 H., Labombard, Brian, Terry, James L., Hughes, Jerry W., Brunner, Daniel Frederic, Payne, Joshua E., Reinke, Matthew Logan, Cziegler, Istvan, Granetz, Robert S., Greenwald, Martin J., Irby, James Henderson, Lin, Yijun, Lipschultz, Bruce, Ma, Yunxing, Marmar, Earl S., Tsujii, Naoto, Wallace, Gregory Marriner, Whyte, Dennis G., Wolfe, Stephen M., Wukitch, Stephen James, Rowan, W. L., Wurden, G., 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 H., Labombard, Brian, Terry, James L., Hughes, Jerry W., Brunner, Daniel Frederic, Payne, Joshua E., Reinke, Matthew Logan, Cziegler, Istvan, Granetz, Robert S., Greenwald, Martin J., Irby, James Henderson, Lin, Yijun, Lipschultz, Bruce, Ma, Yunxing, Marmar, Earl S., Tsujii, Naoto, Wallace, Gregory Marriner, Whyte, Dennis G., Wolfe, Stephen M., Wukitch, Stephen James, Rowan, W. L., and Wurden, G.

Abstract

Parametric dependences of the heat flux footprint on the outer divertor target plate are explored in EDA H-mode and ohmic L-mode plasmas over a wide range of parameters with attached plasma conditions. Heat flux profile shapes are found to be independent of toroidal field strength, independent of power flow along magnetic field lines and insensitive to x-point topology (single-null versus double-null). The magnitudes and widths closely follow that of the “upstream” pressure profile, which are correlated to plasma thermal energy content and plasma current. Heat flux decay lengths near the strike-point in H- and L-mode plasmas scale approximately with the inverse of plasma current, with a diminished dependence at high collisionality in L-mode. Consistent with previous studies, pressure gradients in the boundary scale with plasma current squared, holding the magnetohydrodynamic ballooning parameter approximately invariant at fixed collisionality—strong evidence that critical-gradient transport physics plays a key role in setting the power exhaust channel., United States. Dept. of Energy (Award DE-AC52-06NA25396), United States. Dept. of Energy (Coop. Agreement DE-FC02-99ER54512)

Published
2011

34. Absorption of lower hybrid waves in the scrape off layer of a diverted tokamak

Author

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. Plasma Science and Fusion Center, Whyte, Dennis G., Wallace, Gregory Marriner, Parker, Ronald R., Bonoli, Paul T., Hubbard, Amanda E., Hughes, Jerry W., LaBombard, Brian, Meneghini, Orso-Maria Cornelio, Schmidt, Andrea Elizabeth, Shiraiwa, Shunichi, Wright, John C., Wukitch, Stephen James, Harvey, R. W., Smirnov, A. P., Wilson, J. R., 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. Plasma Science and Fusion Center, Whyte, Dennis G., Wallace, Gregory Marriner, Parker, Ronald R., Bonoli, Paul T., Hubbard, Amanda E., Hughes, Jerry W., LaBombard, Brian, Meneghini, Orso-Maria Cornelio, Schmidt, Andrea Elizabeth, Shiraiwa, Shunichi, Wright, John C., Wukitch, Stephen James, Harvey, R. W., Smirnov, A. P., and Wilson, J. R.

Abstract

The goal of the Lower Hybrid Current Drive (LHCD) system on the Alcator C-Mod tokamak [ Hutchinson et al., Phys. Plasmas 1, 1511 (1994) ] is to investigate current profile control under plasma conditions relevant to future tokamak experiments. Experimental observations of a LHCD “density limit” for C-Mod are presented in this paper. Bremsstrahlung emission from relativistic fast electrons in the core plasma drops suddenly above line averaged densities of 10[superscript 20] m[superscript −3] (ω/ω[subscript LH] ~ 3–4), well below the density limit previously observed on other experiments (ω/ωLH ∼ 2). Electric currents flowing through the scrape off layer (SOL) between the inner and outer divertors increase dramatically across the same density range that the core bremsstrahlung emission drops precipitously. These experimental x-ray data are compared to both conventional modeling, which gives poor agreement with experiment above the density limit and a model including collisional absorption in the SOL, which dramatically improves agreement with experiment above the observed density limit. These results show that strong absorption of LH waves in the SOL is possible on a high density tokamak and the SOL must be included in simulations of LHCD at high density., United States. Dept. of Energy (contract DE-FC02-99ER54512), United States. Dept. of Energy (contract DE-AC02-76CH03073)

Published
2011

35. Modification of current profile, toroidal rotation and pedestal by lower hybrid waves in Alcator C-Mod

Author

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

36. Edge Temperature Gradient as Intrinsic Rotation Drive in Alcator C-Mod Tokamak Plasmas

Author

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

37. Control of Internal Profiles via LHCD on Alcator C-Mod

Author

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, Porkolab, Miklos, Parker, Ronald R., Hubbard, Amanda E., Hughes, Jerry W., Bonoli, Paul T., Ince-Cushman, Alexander, Ko, J. S., Meneghini, Orso-Maria Cornelio, Reinke, Matthew Logan, Rice, John E., Schmidt, Andrea Elizabeth, Shiraiwa, Shunichi, Wallace, Gregory Marriner, Wright, John C., Wilson, J. R., Kessel, C., Scott, S., 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, Porkolab, Miklos, Parker, Ronald R., Hubbard, Amanda E., Hughes, Jerry W., Bonoli, Paul T., Ince-Cushman, Alexander, Ko, J. S., Meneghini, Orso-Maria Cornelio, Reinke, Matthew Logan, Rice, John E., Schmidt, Andrea Elizabeth, Shiraiwa, Shunichi, Wallace, Gregory Marriner, Wright, John C., Wilson, J. R., Kessel, C., and Scott, S.

Abstract

LHCD on Alcator C-Mod is being used in plasmas with parameters similar to those expected on ITER for the purpose of tailoring the plasma current profile. LHCD experiments have also produced intriguing results related to momentum transport and edge pedestal physics that affect the toroidal rotation profile and the temperature and density profiles. Quantitative comparisons between local measurements and theory/simulation have been performed, confirming the off-axis localization of the current drive, as well as its magnitude and location dependence on the launched n|| spectrum and electron temperature. Applying LHCD during the current ramp saves volt-seconds and delays the peaking of the current profile. Counter current toroidal rotation during LHCD has been observed in both L and H-mode plasmas. In H-mode plasmas the edge pedestal collisionality is reduced while the overall pressure in the pedestal increases slightly., United States. Dept. of Energy (Contract No. DE-AC02-09CH11466), United States. Dept. of Energy (Contract No. DE-FC02-99ER54512)

Published
2011

38. Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod Plasmas

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Lipschultz, Bruce, McDermott, R. M., Hughes, Jerry W., Catto, Peter J., Hubbard, Amanda E., Granetz, Robert S., Greenwald, Martin J., Labombard, Brian, Marr, K., Rice, John E., Whyte, Dennis G., Alcator C-Mod Team, Reinke, Matthew Logan, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Lipschultz, Bruce, McDermott, R. M., Hughes, Jerry W., Catto, Peter J., Hubbard, Amanda E., Granetz, Robert S., Greenwald, Martin J., Labombard, Brian, Marr, K., Rice, John E., Whyte, Dennis G., Alcator C-Mod Team, and Reinke, Matthew Logan

Abstract

High-resolution charge-exchange recombination spectroscopic measurements of B[superscript 5+] ions have enabled the first spatially resolved calculations of the radial electric field (E[subscript r]) in the Alcator C-Mod pedestal region [ E. S. Marmar, Fusion Sci. Technol. 51, 261 (2006) ]. These observations offer new challenges for theory and simulation and provide for important comparisons with other devices. Qualitatively, the field structure observed on C-Mod is similar to that on other tokamaks. However, the narrow high-confinement mode (H-mode) E[subscript r] well widths (5 mm) observed on C-Mod suggest a scaling with machine size, while the observed depths (up to 300 kV/m) are unprecedented. Due to the strong ion-electron thermal coupling in the C-Mod pedestal, it is possible to infer information about the main ion population in this region. The results indicate that in H-mode the main ion pressure gradient is the dominant contributor to the Er well and that the main ions have significant edge flow. C-Mod H-mode data show a clear correlation between deeper E[subscript r] wells, higher confinement plasmas, and higher electron temperature pedestal heights. However, improved L-mode (I-mode) plasmas exhibit energy confinement equivalent to that observed in similar H-mode discharges, but with significantly shallower E[subscript r] wells. I-mode plasmas are characterized by H-mode-like energy barriers, but with L-mode-like particle barriers. The decoupling of energy and particle barrier formation makes the I-mode an interesting regime for fusion research and provides for a low collisionality pedestal without edge localized modes., United States Department of Energy (Cooperative Agreement No. DE-FC02-99ER54512)

Published
2010

39. Observation of Self-Generated Flows in Tokamak Plasmas with Lower-Hybrid-Driven Current

Author

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 H., Rice, John E., Ince-Cushman, Alexander, Reinke, Matthew Logan, Greenwald, Martin J., Wallace, Gregory Marriner, Parker, Ronald R., Fiore, Catherine L., Hughes, Jerry W., Bonoli, Paul T., Shiraiwa, Shunichi, Hubbard, Amanda E., Wolfe, Stephen M., Marmar, Earl S., Bitter, M., Wilson, J., Hill, K., Parker, R., Fiore, Catherine, Hughes Jr, Jerry, Hubbard, Amanda E, Wolfe, Stephen M, Hutchinson, Ian Horner, 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 H., Rice, John E., Ince-Cushman, Alexander, Reinke, Matthew Logan, Greenwald, Martin J., Wallace, Gregory Marriner, Parker, Ronald R., Fiore, Catherine L., Hughes, Jerry W., Bonoli, Paul T., Shiraiwa, Shunichi, Hubbard, Amanda E., Wolfe, Stephen M., Marmar, Earl S., Bitter, M., Wilson, J., Hill, K., Parker, R., Fiore, Catherine, Hughes Jr, Jerry, Hubbard, Amanda E, Wolfe, Stephen M, and Hutchinson, Ian Horner

Abstract

In Alcator C-Mod discharges lower hybrid waves have been shown to induce a countercurrent change in toroidal rotation of up to 60 km/s in the central region of the plasma (r/a~<0.4). This modification of the toroidal rotation profile develops on a time scale comparable to the current redistribution time (~100 ms) but longer than the energy and momentum confinement times (~20 ms). A comparison of the co- and countercurrent injected waves indicates that current drive (as opposed to heating) is responsible for the rotation profile modifications. Furthermore, the changes in central rotation velocity induced by lower hybrid current drive (LHCD) are well correlated with changes in normalized internal inductance. The application of LHCD has been shown to generate sheared rotation profiles and a negative increment in the radial electric field profile consistent with a fast electron pinch., U. S. Department of Energy (Contract No. DE-FC02- 99ER54512-CMOD)

Published
2010

40. Edge transport barrier studies on the Alcator C-Mod tokamak

Author

Dmitri Mossessian., Massachusetts Institute of Technology. Dept. of Nuclear Engineering., Hughes, Jerry W. (Jerry Wayne), 1975, Dmitri Mossessian., Massachusetts Institute of Technology. Dept. of Nuclear Engineering., and Hughes, Jerry W. (Jerry Wayne), 1975

Abstract

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2005., Includes bibliographical references (p. 211-226)., Edge transport barriers (ETBs) in tokamak plasmas accompany transitions from low confinement (L-mode) to high confinement (H-mode) and exhibit large density and temperature gradients in a narrow pedestal region near the last closed flux surface (LCFS). Because tokamak energy confinement depends strongly on the boundary condition imposed by the edge plasma pressure, one desires a predictive capability for the pedestal on a future tokamak. On Alcator C-Mod, significant contributions to ETB studies were made possible with edge Thomson scattering (ETS), which measures profiles of electron temperature (20 Te[eV] 800) and density (0.3 ne[1020m-3] ' 5) with 1.3-mm spatial resolution near the LCFS. Profiles of Te, ne, and Pe = neTe are fitted with a parameterized function, revealing typical pedestal widths A of 2-6mm, with ATe Ane, on average. Pedestals are examined to determine existence criteria for the enhanced D, (EDA) H-mode. A feature that distinguishes this regime is a quasi-coherent mode (QCM) near the LCFS. The presence or absence of the QCM is related to edge conditions, in particular density, temperature and safety factor q. Results are consistent with higher values of both q and collisionality v* giving the EDA regime. Further evidence suggests that increased Vpel may favor the QCM; thus EDA may have relevance to low-v* reactor regimes, should sufficient edge pressure gradient exist., (cont.) Scaling studies of pedestal parameters and plasma confinement in EDA H-modes varied operational parameters such as current Ip and L-mode target density ne,L. At fixed plasma shape, widths show little systematic variation with plasma parameters. Scalings are however determined for pedestal heights and gradients. The Pe pedestal height and gradient both scale as I, similar to scalings found on other tokamaks, though with differing pedestal-limiting physics. It is seen that the density pedestal value ne,PED scales linearly with Ip, and more weakly with h,L, indicating that neutral fueling plays a relatively limited role in setting H-mode density. Plasma stored energy scales in a linear fashion with the Pe pedestal, such that empirical confinement scalings are affected by edge pedestal scalings. Empirical determination of neutral density and ionization source was made across the pedestal region, enabling inference of neutral gradient scale length Lo and effective diffusivity Def. The Def well is comparable in width to the pedestal, and Lo tends to be less than Ane. Computation of Lo in discharges with varying ne,L yields a similar result, suggesting that A,, is generally set by the ETB extent and not neutral penetration length. Puffing gas into an existing H-mode edge yields no significant change in the values of ne,PED, Vne, which is qualitatively consistent with simulations using a coupled fluid-kinetic neutral model. Experiment and modeling indicate the importance of thermal equilibration of neutrals with ions, particularly in high density collisional) plasmas., by Jerry W. Hugues, Jr., Ph.D.

Published
2006

41. Inboard and outboard radial electric field wells in the H- and I-mode pedestal of Alcator C-Mod and poloidal variations of impurity temperature

Author

Matt Landreman, Randy Michael Churchill, Christian Theiler, J.R. Walk, Matthew Reinke, D.R. Ernst, Amanda Hubbard, Jerry Hughes, Ian H. Hutchinson, Felix I. Parra, Bruce Lipschultz, Earl Marmar, J. T. Terry, Peter J. Catto, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Theiler, Christian, Churchill, Randy Michael, Lipschultz, Bruce, Ernst, Darin R., Hughes, Jerry W., Jr., Catto, Peter J., Reinke, Matthew Logan, Hubbard, Amanda E., Marmar, Earl S., Terry, J. T., and Walk, John R.

Subjects
Nuclear and High Energy Physics, Electron density, media_common.quotation_subject, Flux, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Asymmetry, poloidal asymmetries, 010305 fluids & plasmas, Pedestal, Optics, radial electric field well, Alcator C-Mod, Physics::Plasma Physics, Impurity, Electric field, 0103 physical sciences, Physics::Atomic Physics, 010306 general physics, media_common, edge transport barrier, Physics, business.industry, I-mode, Plasma, Condensed Matter Physics, Atomic physics, business
Abstract

We present inboard (HFS) and outboard (LFS) radial electric field (E[subscript r]) and impurity temperature (T[subscript z]) measurements in the I-mode and H-mode pedestal of Alcator C-Mod. These measurements reveal strong Er wells at the HFS and the LFS midplane in both regimes and clear pedestals in T[subscript z], which are of similar shape and height for the HFS and LFS. While the H-mode E[subscript r] well has a radially symmetric structure, the E[subscript r] well in I-mode is asymmetric, with a stronger ExB shear layer at the outer edge of the E[subscript r] well, near the separatrix. Comparison of HFS and LFS profiles indicates that impurity temperature and plasma potential are not simultaneously flux functions. Uncertainties in radial alignment after mapping HFS measurements along flux surfaces to the LFS do not, however, allow direct determination as to which quantity varies poloidally and to what extent. Radially aligning HFS and LFS measurements based on the T[subscript z] profiles would result in substantial inboard-outboard variations of plasma potential and electron density. Aligning HFS and LFS E[subscript r] wells instead also approximately aligns the impurity poloidal flow profiles, while resulting in a LFS impurity temperature exceeding the HFS values in the region of steepest gradients by up to 70%. Considerations based on a simplified form of total parallel momentum balance and estimates of parallel and perpendicular heat transport time scales seem to favor an approximate alignment of the E[subscript r] wells and a substantial poloidal asymmetry in impurity temperature., United States. Dept. of Energy (Cooperative Agreement DE-FC02-99ER54512), Swiss National Science Foundation

Published
2016

42. Correlation ECE diagnostic in Alcator C-Mod

Author

Rui Vieira, C. Gao, John Rice, Randy Michael Churchill, Miklos Porkolab, Matthew Reinke, Curran Oi, James Irby, Amanda Hubbard, Paul Ennever, Anne White, D. R. Mikkelsen, Martin Greenwald, J.R. Walk, Nathaniel Thomas Howard, Christian Theiler, Choongki Sung, R. Leccacorvi, Jerry Hughes, 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, Sung, Choongki, White, Anne E., Howard, Nathaniel Thomas, Irby, James Henderson, Leccacorvi, Rick, Vieira, Rui F., Oi, Curran, Rice, John E., Reinke, Matthew Logan, Gao, Chi, Ennever, Paul Chappell, Porkolab, Miklos, Churchill, Randy, Theiler, Christian, Walk, John R., Jr., Hughes, Jerry W., Jr., Hubbard, Amanda E., and Greenwald, Martin J.

Subjects
Core (optical fiber), Pedestal, Alcator C-Mod, Turbulence, Chemistry, Physics, QC1-999, Electron temperature, Plasma, Atomic physics, Rotation, Ohmic contact
Abstract

Correlation ECE (CECE) is a diagnostic technique that allows measurement of small amplitude electron temperature, T[subscript e], fluctuations through standard cross-correlation analysis methods. In Alcator C-Mod, a new CECE diagnostic has been installed[Sung RSI 2012], and interesting phenomena have been observed in various plasma conditions. We find that local T[subscript e] fluctuations near the edge (ρ ~ 0:8) decrease across the linearto- saturated ohmic confinement transition, with fluctuations decreasing with increasing plasma density[Sung NF 2013], which occurs simultaneously with rotation reversals[Rice NF 2011]. T[subscript e] fluctuations are also reduced across core rotation reversals with an increase of plasma density in RF heated L-mode plasmas, which implies that the same physics related to the reduction of T[subscript e] fluctuations may be applied to both ohmic and RF heated L-mode plasmas. In I-mode plasmas, we observe the reduction of core T[subscript e] fluctuations, which indicates changes of turbulence occur not only in the pedestal region but also in the core across the L/I transition[White NF 2014]. The present CECE diagnostic system in C-Mod and these experimental results are described in this paper.

Published
2015

43. Edge-localized mode avoidance and pedestal structure in I-mode plasmas

Author

Istvan Cziegler, Seung Gyou Baek, P.B. Snyder, Matthew Reinke, Arturo Dominguez, J. E. Rice, J.R. Walk, D. G. Whyte, Randy Michael Churchill, T.H. Osborne, Jerry Hughes, J.L. Terry, Anne White, A.E. Hubbard, Christian Theiler, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Walk Jr, John R., Hughes, Jerry W., Jr., Hubbard, Amanda E., Terry, James L., Whyte, Dennis G., White, A. E., Baek, Seung Gyou, Reinke, Matthew Logan, Rice, John E., Theiler, C., and Churchill, Randy Michael

Subjects
Physics, Tokamak, Turbulence, Physics::Instrumentation and Detectors, Drop (liquid), Extrapolation, Plasma, Condensed Matter Physics, law.invention, Computational physics, Pedestal, law, Physics::Plasma Physics, Atomic physics, Magnetohydrodynamics, Edge-localized mode
Abstract

I-mode is a high-performance tokamak regime characterized by the formation of a temperature pedestal and enhanced energy confinement, without an accompanying density pedestal or drop in particle and impurity transport. I-mode operation appears to have naturally occurring suppression of large Edge-Localized Modes (ELMs) in addition to its highly favorable scalings of pedestal structure and overall performance. Extensive study of the ELMy H-mode has led to the development of the EPED model, which utilizes calculations of coupled peeling-ballooning MHD modes and kinetic-ballooning mode (KBM) stability limits to predict the pedestal structure preceding an ELM crash. We apply similar tools to the structure and ELM stability of I-mode pedestals. Analysis of I-mode discharges prepared with high-resolution pedestal data from the most recent C-Mod campaign reveals favorable pedestal scalings for extrapolation to large machines—pedestal temperature scales strongly with power per particle P[subscript net] [over [bar over n][subscript e]], and likewise pedestal pressure scales as the net heating power (consistent with weak degradation of confinement with heating power). Matched discharges in current, field, and shaping demonstrate the decoupling of energy and particle transport in I-mode, increasing fueling to span nearly a factor of two in density while maintaining matched temperature pedestals with consistent levels of P[subscript net] [over [bar over n][subscript e]]. This is consistent with targets for increased performance in I-mode, elevating pedestal β [subscript p] and global performance with matched increases in density and heating power. MHD calculations using the ELITE code indicate that I-mode pedestals are strongly stable to edge peeling-ballooning instabilities. Likewise, numerical modeling of the KBM turbulence onset, as well as scalings of the pedestal width with poloidal beta, indicates that I-mode pedestals are not limited by KBM turbulence—both features identified with the trigger for large ELMs, consistent with the observed suppression of large ELMs in I-mode., United States. Dept. of Energy (Agreement DE-FC02-99ER54512), United States. Dept. of Energy (Agreement DE-FG02-99ER54309)

Published
2013

44. Constraining the divertor heat width in ITER

Author

J.G. Watkins, Brian LaBombard, Bruce Lipschultz, J.L. Terry, Dennis G. Whyte, P.C. Stangeby, A.W. Leonard, Dan Brunner, D. Elder, Jerry Hughes, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis G., Labombard, Brian, Hughes, Jerry W., Jr., Lipschultz, Bruce, Terry, James L., and Brunner, Daniel Frederic

Subjects
Physics, Nuclear and High Energy Physics, Physical reasoning, Separatrix, Divertor, Mechanics, Plasma, Pedestal, Nuclear Energy and Engineering, Power Balance, Heat transmission, Momentum conservation, General Materials Science, Atomic physics
Abstract

A model is developed which constrains heat width, λr based on global power balance, momentum conservation, pedestal stability and sheath heat transmission. The model relies on measurements of the ratio of separatrix to pedestal pressure; a ratio ∼5% is found to be expected for ITER. Applying this model indicates a constraint that the allowed λr ∼ 10–30 mm for ITER if the divertor is in the high-recycling regime as expected (T < 20 eV) while a λr ∼ 1–3 mm requires a separatrix pressure approximately equal to the top pedestal pressure in violation of physical reasoning and the concept of a pedestal. A weaker constraint is applied in the model that upstream separatrix temperature simultaneously satisfies power balance. The constrained model cannot satisfy power balance with λr < 3 mm, and in order to obtain λr ∼ 5 mm requires divertor plasma temperature >100 eV, a condition which would have very negative consequences for the divertor, but has never been observed experimentally., United States. Department of Defense (US DOE award DE-SC00-02060), United States. Department of Defense (contract DE-FC02-99ER54512), United States. Department of Defense (cooperative agreement DE-FC02- 04ER54698)

Published
2013

45. Density sensitivity of intrinsic rotation profiles in ion cyclotron range of frequency-heated L-mode plasmas

Author

A.E. Hubbard, Martin Greenwald, John Rice, Paul Ennever, Anne White, C. Gao, Matthew Reinke, Jerry Hughes, Nathan Howard, 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, Reinke, Matthew Logan, Rice, John E., White, Anne E., Greenwald, Martin J., Howard, Nathaniel Thomas, Ennever, Paul Chappell, Hubbard, Amanda E., Hughes, Jerry W., and Gao, Chi

Subjects
Physics, Electron density, Tokamak, Cyclotron, Resonance, Plasma, Condensed Matter Physics, Rotation, law.invention, Ion, Momentum, Nuclear Energy and Engineering, law, Physics::Plasma Physics, Physics::Space Physics, Atomic physics
Abstract

The physical mechanisms that cause tokamak plasmas to rotate toroidally without external momentum input are of considerable interest to the plasma physics community. This paper documents a substantial change in both the magnitude of the core-rotation frequency, −1 < ω(r/a = 0) < +10 kHz, and the sign of rotation shear at mid-radius, u' = −R[superscript 2] dω/dr/v[subscript th,i], which varies in the range −0.6 < u' < +0.8 in response to very small changes in the electron density. In 0.8 MA, 5.4 T Alcator C-Mod L-mode plasmas using 1.2 MW of on-axis ion-cyclotron resonance heating, plasmas with line-averaged densities in the range 1.0 < [bar over n][subscript e] < 1.2 X 10[superscript 20] m[superscript -3] exhibit a transition from a peaked intrinsic rotation profile to one that is hollow. Gradient scale lengths of the temperature and density profiles, the drive for plasma turbulence thought to play a role in intrinsic rotation, are indistinguishable within experimental uncertainties between the plasmas, and linear stability analysis using GYRO shows the plasmas to be in the ion temperature gradient-dominated turbulence regime. The impact of changes in the rotation profile in response to minor changes under target plasma conditions is discussed in relation to established analysis techniques and cross-machine rotation scaling studies, with comparisons made with existing ASDEX-Upgrade work on intrinsic rotation shear., United States. Dept. of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy. Office of Fusion Energy Sciences (Postdoctoral Research Program)

Published
2012

46. Poloidal variation of high-Z impurity density due to hydrogen minority ion cyclotron resonance heating on Alcator C-Mod

Author

Stephen Wukitch, John Rice, Amanda Hubbard, J. W. Hughes, Y. Podpaly, Yijun Lin, Ian H. Hutchinson, Nathaniel Thomas Howard, A. Bader, David Pace, Matthew Reinke, 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., and Podpaly, Yuri

Subjects
Materials science, Tokamak, Cyclotron, Resonance, Condensed Matter Physics, law.invention, Ion, Nuclear Energy and Engineering, Alcator C-Mod, Impurity, law, Physics::Plasma Physics, Electric potential, Atomic physics, Ion cyclotron resonance
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
2012

47. Lower hybrid current drive at high density in the multi-pass regime

Author

Ian Faust, John Wright, Ye Ma, G.M. Wallace, Andrea Schmidt, Brian LaBombard, S. Shiraiwa, D.G. Whyte, Alexander Smirnov, Orso Meneghini, A.E. Hubbard, James R. Wilson, S. G. Baek, P.T. Bonoli, Jerry Hughes, S.J. Wukitch, R.R. Parker, Cornwall Lau, Matthew Reinke, R. W. Harvey, J.L. Terry, 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. Plasma Science and Fusion Center, Wallace, Gregory Marriner, Faust, Ian Charles, Meneghini, Orso-Maria Cornelio, Parker, Ronald R., Shiraiwa, Shunichi, Baek, Seung Gyou, Bonoli, Paul T., Hubbard, Amanda E., Hughes, Jerry W., Labombard, Brian, Lau, C., Ma, Y., Reinke, Matthew Logan, Terry, James L., Whyte, Dennis G., Wright, John C., Wukitch, Stephen James, and Schmidt, A. E.

Subjects
Physics, Tokamak, law, Ionization, Fokker–Planck equation, Electron, Plasma, Atomic physics, Current (fluid), Condensed Matter Physics, Magnetic field, Bootstrap current, law.invention
Abstract

Assessing the performance of lower hybrid current drive (LHCD) at high density is critical for developing non-inductive current drive systems on future steady-state experiments. Excellent LHCD efficiency has been observed during fully non-inductive operation (η = 2.0 − 2.5 × 10[superscript 19] AW[superscript –1] m[superscript –2] at [¯ over n][subscript e] = 0.5 × 10[superscript 20] m[superscript –3]) on Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas1, 1511 (1994)] under conditions (n[subscript e], magnetic field and topology, and LHCD frequency) relevant to ITER [S. Shiraiwa et al., Nucl. Fusion 51, 103024 (2011)]. To extend these results to advanced tokamak regimes with higher bootstrap current fractions on C-Mod, it is necessary to increase [¯ over n][subscript e] to 1.0 − 1.5 × 10[superscript 20] m[superscript −3]. However, the number of current-carrying, non-thermal electrons generated by LHCD drops sharply in diverted configurations at densities that are well below the density limit previously observed on limited tokamaks. In these cases, changes in scrape off layer (SOL)ionization and density profiles are observed during LHCD, indicating that significant power is transferred from the LH waves to the SOL.Fokker-Planck simulations of these discharges utilizing ray tracing and full wave propagation codes indicate that LH waves in the high density, multi-pass absorption regime linger in the plasma edge, and SOL region, where absorption near or outside the LCFS results in the loss of current drive efficiency. Modeling predicts that non-thermal emission increases with stronger single-pass absorption. Experimental data show that increasing T[subscript e] in high density LH discharges results in higher non-thermal electron emission, as predicted by the models., United States. Dept. of Energy (Award DE-FC02-99ER54512), United States. Dept. of Energy (Award DE-AC02-09CH11466)

Published
2011

48. 20 years of research on the Alcator C-Mod tokamaka)

Author

Istvan Cziegler, R. M. McDermott, John Goetz, R.F. Vieira, Robert Granetz, Amanda Hubbard, S. Horne, Ian H. Hutchinson, Nathan Howard, C. K. Li, Robert Mumgaard, E. Edlund, Arturo Dominguez, A. Tronchin-James, Paul Ennever, Theodore Golfinopoulos, C. Gao, John Rice, J. H. Irby, S. Pitcher, Thomas W. Fredian, James Myra, R.R. Parker, N. Smick, Stewart Zweben, D. R. Mikkelsen, Bruce Lipschultz, Olaf Grulke, W. Bergerson, D. Terry, Aaron Bader, D.G. Whyte, V.A. Izzo, Yuichi Takase, Z.S. Hartwig, Brian LaBombard, Harold Barnard, James R. Wilson, W. Burke, S.J. Wukitch, Vincent Tang, G. McCracken, D.R. Ernst, J. M. Sierchio, G.M. Olynyk, Igor Bespamyatnov, W. Beck, C.L. Fiore, Christian Theiler, Jeff Candy, Joshua Stillerman, Dan Brunner, S.M. Wolfe, P.T. Bonoli, Jerry Hughes, A. Loarte, Andrea Schmidt, Choongki Sung, B. P. Duval, John Wright, Odd Erik Garcia, Gregory Wallace, Mohammad Reza Bakhtiari, D. L. Brower, R. Ochoukov, Ian Faust, S. Shiraiwa, A. Mazurenko, Earl Marmar, W. L. Rowan, Anne White, Ahmed Diallo, D. A. Mossessian, Miklos Porkolab, J.L. Terry, C.E. Kessel, Naoto Tsujii, P. B. Snyder, G.M. Wright, J. A. Snipes, Seung Gyou Baek, E. Nelson-Melby, Martin Greenwald, Yuri Podpaly, Brandon Sorbom, Yu-Ming Lin, Cornwall Lau, Matthew Reinke, Orso Meneghini, J.R. Walk, S. D. Scott, M. Churchill, 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, Greenwald, Martin J., Baek, Seung Gyou, Barnard, Harold, Beck, William K., Bonoli, Paul T., Brunner, Daniel Frederic, Burke, William M., Ennever, Paul Chappell, Ernst, Darin R., Faust, Ian Charles, Fiore, Catherine, Fredian, Thomas W., Gao, Chi, Golfinopoulos, Theodore, Granetz, Robert S., Hartwig, Zachary, Hubbard, Amanda E., Hughes, Jerry W., Jr., Hutchinson, Ian H., Irby, James Henderson, Labombard, Brian, Li, Chikang, Lin, Yijun, Marmar, Earl S., Mumgaard, Robert Thomas, Parker, Ronald R., Porkolab, Miklos, Rice, John E., Shiraiwa, Shunichi, Sierchio, Jennifer M., Sorbom, Brandon Nils, Stillerman, Joshua A., Sung, Choongki, Terry, David Rankin, Terry, James L., Vieira, Rui F., Walk, John R., Jr., Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G., Wolfe, Stephen M., Wright, Graham, Wright, John C., and Wukitch, Stephen James

Subjects
Physics, Tokamak, VDP::Mathematics and natural science: 400::Physics: 430::Space and plasma physics: 437, Divertor, Nuclear engineering, Cyclotron, Context (language use), Fusion power, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, Alcator C-Mod, Physics::Plasma Physics, law, VDP::Matematikk og Naturvitenskap: 400::Fysikk: 430::Rom- og plasmafysikk: 437, 0103 physical sciences, Plasma diagnostics, Radio frequency, Atomic physics, 010306 general physics
Abstract

The object of this review is to summarize the achievements of research on the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994) and Marmar, Fusion Sci. Technol. 51, 261 (2007)] and to place that research in the context of the quest for practical fusion energy. C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since it began operation in 1993, contributing data that extends tests of critical physical models into new parameter ranges and into new regimes. Using only high-power radio frequency (RF) waves for heating and current drive with innovative launching structures, C-Mod operates routinely at reactor level power densities and achieves plasma pressures higher than any other toroidal confinement device. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing components—approaches subsequently adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated the critical role of cross-field transport in divertor operation, edge flows and the tokamak density limit. C-Mod developed the I-mode and the Enhanced Dα H-mode regimes, which have high performance without large edge localized modes and with pedestal transport self-regulated by short-wavelength electromagnetic waves. C-Mod has carried out pioneering studies of intrinsic rotation and demonstrated that self-generated flow shear can be strong enough in some cases to significantly modify transport. C-Mod made the first quantitative link between the pedestal temperature and the H-mode's performance, showing that the observed self-similar temperature profiles were consistent with critical-gradient-length theories and followed up with quantitative tests of nonlinear gyrokinetic models. RF research highlights include direct experimental observation of ion cyclotron range of frequency (ICRF) mode-conversion, ICRF flow drive, demonstration of lower-hybrid current drive at ITER-like densities and fields and, using a set of novel diagnostics, extensive validation of advanced RF codes. Disruption studies on C-Mod provided the first observation of non-axisymmetric halo currents and non-axisymmetric radiation in mitigated disruptions. A summary of important achievements and discoveries are included., United States. Dept. of Energy (Cooperative Agreement DE-FC02-99ER54512), United States. Dept. of Energy (Cooperative Agreement DE-FG03-94ER-54241), United States. Dept. of Energy (Cooperative Agreement DE-AC02-78ET- 51013), United States. Dept. of Energy (Cooperative Agreement DE-AC02-09CH11466), United States. Dept. of Energy (Cooperative Agreement DE-FG02-95ER54309), United States. Dept. of Energy (Cooperative Agreement DE-AC02-05CH11231), United States. Dept. of Energy (Cooperative Agreement DE-AC52-07NA27344), United States. Dept. of Energy (Cooperative Agreement DE-FG02- 97ER54392), United States. Dept. of Energy (Cooperative Agreement DE-SC00-02060)

Published
2014
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49. Non-neoclassical up/down asymmetry of impurity emission on Alcator C-Mod

Author

Matthew Reinke, Nathaniel Thomas Howard, J.L. Terry, James Irby, John Rice, Anne White, Martin Greenwald, Yuri Podpaly, Jerry Hughes, Ian H. Hutchinson, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian, Reinke, Matthew Logan, Rice, John E., Hutchinson, Ian H., Greenwald, Martin J., Howard, Nathaniel Thomas, Hughes, Jerry W., Irby, James Henderson, Podpaly, Yuri, Terry, James L., and White, Anne E.

Subjects
Physics, Nuclear and High Energy Physics, Toroid, Condensed matter physics, media_common.quotation_subject, Tore Supra, Condensed Matter Physics, Computer Science::Digital Libraries, Asymmetry, Alcator C-Mod, Physics::Plasma Physics, Impurity, Atomic physics, Ohmic contact, Scaling, Computer Science::Databases, Dimensionless quantity, media_common
Abstract

We demonstrate that existing theories are insufficient to explain up/down asymmetries of argon x-ray emission in Alcator C-Mod ohmic plasmas. Instead of the poloidal variation, ñ[subscript z]/〈n[subscript z]〉, being of order the inverse aspect ratio, ϵ, and scaling linearly with B[subscript t][superscript _ over n][subscript e]/I[2 over p], it is observed over 0.8 < r/a < 1.0 to be of order unity and exhibits a threshold behaviour between 3.5, United States. Dept. of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy (Fusion Research Postdoctoral Research Program)

Published
2013
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50. Investigation of the Thomson scattering-ECE discrepancy in ICRF heated plasmas at Alcator C-Mod

Author

S.J. Wukitch, M. L. Reinke, Amanda Hubbard, R. W. Harvey, Ye Ma, Anne White, Yuxuan Lin, A. Bader, Max E Austin, P.T. Bonoli, Jerry Hughes, S.M. Wolfe, 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, White, Anne E., Hubbard, Amanda E., Hughes, Jerry W., Bonoli, Paul T., Bader, Andrew, Lin, Yijun, Ma, Y., Wolfe, Stephen M., and Wukitch, Stephen James

Subjects
Nuclear and High Energy Physics, Tokamak, Materials science, Thomson scattering, Cyclotron, Electron, Condensed Matter Physics, law.invention, Ion, Alcator C-Mod, law, Electron temperature, Atomic physics, Ion cyclotron resonance
Abstract

This paper reports on new experiments at Alcator C-Mod that were performed in order to investigate the long-standing, unresolved discrepancy between Thomson scattering (TS) and electron cyclotron emission (ECE) measurements of electron temperature in high temperature tokamak plasmas. Ion cyclotron range of frequency (ICRF) heating is used to produce high temperature conditions where the type of TS-ECE discrepancy observed in the past at JET and TFTR should become observable. At Alcator C-Mod, plasmas with Te(0) up to 8 keV are obtained using ion cyclotron resonance heating (ICRH), ICRF mode conversion heating and a combination of the two heating methods in order to explore the hypothesis that the presence of ICRH-generated fast ions may be related to the discrepancy. In all high temperature cases, the TS and ECE measurements of electron temperature agree to within experimental uncertainties. We find no evidence for the type of discrepancy reported at JET and TFTR. These results show that the TS-ECE discrepancy does not depend on high temperatures alone and also that the presence of ICRH-generated fast ions is insufficient to cause the TS-ECE discrepancy., United States. Dept. of Energy (DE-FC02-99ER54512)

Published
2012
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