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Title: Progress in extending high poloidal beta scenarios on DIII-D towards a steady-state fusion reactor and impact of energetic particles

Abstract

To prepare for steady-state operation of future fusion reactors (e.g. the International Thermonuclear Experimental Reactor and China Fusion Engineering Test Reactor (CFETR)), experiments on DIII-D have extended the high poloidal beta (βP) scenario to reactor-relevant edge safety factor q95 ~ 6.0, while maintaining a large-radius internal transport barrier (ITB) using negative magnetic shear. Excellent energy confinement quality (H98y2 > 1.5) is sustained at high normalized beta (βN ~ 3.5). This high-performance ITB state with Greenwald density fraction near 100% and qmin ≥ 3 is achieved with toroidal plasma rotation Vtor ~ 0 at ρ ≥ 0.6. This is a key result for reactors expected to have low Vtor. At high βP (≥1.9), large Shafranov shift can stabilize turbulence leading to a high confinement state with a low pedestal and an ITB. At lower βP (<1.9), negative magnetic shear in the plasma core contributes to turbulence suppression and can compensate for reduced Shafranov shift to continue to access a large-radius ITB and excellent confinement with low Vtor, consistent with the results of gyrofluid transport simulations. These high-βP cases are characterized by weak/no Alfvén eigenmodes (a.e.) and classical fast-ion transport. At high density, the fast-ion deceleration time decreases and Δβfast is lower; these reduce a.e. drive. The reverse-shear Alfvén eigenmodes are weaker or stable because the negative magnetic shear region is located at higher radius, away from the peaked fast-ion profile. Resistive wall modes can be a limitation at simultaneous high βN, low internal inductance, and low rotation. Analysis suggests that additional off-axis external current drive could provide a more stable path at reduced q95. Based on a DIII-D high-βP plasma with large-radius ITB, two scenarios are proposed for CFETR Q = 5 steady-state operation with ~1 GW fusion power: a lower-$${l_i}{\text{ }}$$ ($${l_i}$$ ~ 0.66) and a higher-$${l_i}$$ ($${l_i}$$ ~ 0.75) case. Using a Landau closure model, multiple energetic particle (EP) effects on the a.e. stability are analyzed modifying the growth rate of the a.e.s triggered by the neutral-beam-injection EPs and alpha particles, although the stabilizing/destabilizing effect is weak for the cases analyzed. The stabilizing effects of the combined EP species β, energy, and density profile in CFETR need further investigation.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [1];  [1]; ORCiD logo [1]; ORCiD logo [3]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [4]; ORCiD logo [1];  [1]; ORCiD logo [1];  [2];  [5];  [2]; ORCiD logo [2];  [2];  [2]; ORCiD logo [1] more »;  [1];  [2];  [6];  [2];  [7]; ORCiD logo [2]; ORCiD logo [8];  [5] « less
  1. Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics
  2. General Atomics, San Diego, CA (United States)
  3. Univ. Carlos III de Madrid (Spain)
  4. Shenzhen Univ. (China). Advanced Energy Research Center
  5. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  6. Univ. of Wisconsin, Madison, WI (United States)
  7. Univ. of California, Los Angeles, CA (United States)
  8. Oak Ridge Associated Univ., Oak Ridge, TN (United States)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of Wisconsin, Madison, WI (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of California, Los Angeles, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES); National Natural Science Foundation of China (NSFC); Anhui Provincial Natural Science Foundation
OSTI Identifier:
1666382
Alternate Identifier(s):
OSTI ID: 1664598; OSTI ID: 1797656; OSTI ID: 1798020
Report Number(s):
LLNL-JRNL-812779
Journal ID: ISSN 0029-5515
Grant/Contract Number:  
FC02-04ER54698; AC52-07NA27344; FG02-08ER54999; AC05-00OR22725; FG02-08ER54984; 11975276; 2008085J04; AC52- 07NA27344; AC05- 00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 60; Journal Issue: 12; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamak; steady state; high bootstrap current; energetic particle; Physics - Plasma physics

Citation Formats

Huang, J., Garofalo, A. M., Qian, J. P., Gong, X. Z., Ding, S. Y., Varela, J., Chen, J. L., Guo, W. F., Li, K., Wu, M. Q., Pan, C. K., Ren, Q., Zhang, B., Lao, L. L., Holcomb, C. T., McClenaghan, J., Weisberg, D., Chan, V., Hyatt, A., Hu, W. H., Li, G. Q., Ferron, J., McKee, G., Pinsker, R. I., Rhodes, T., Staebler, G. M., Spong, D., and Yan, Z.. Progress in extending high poloidal beta scenarios on DIII-D towards a steady-state fusion reactor and impact of energetic particles. United States: N. p., 2020. Web. https://doi.org/10.1088/1741-4326/abaf33.
Huang, J., Garofalo, A. M., Qian, J. P., Gong, X. Z., Ding, S. Y., Varela, J., Chen, J. L., Guo, W. F., Li, K., Wu, M. Q., Pan, C. K., Ren, Q., Zhang, B., Lao, L. L., Holcomb, C. T., McClenaghan, J., Weisberg, D., Chan, V., Hyatt, A., Hu, W. H., Li, G. Q., Ferron, J., McKee, G., Pinsker, R. I., Rhodes, T., Staebler, G. M., Spong, D., & Yan, Z.. Progress in extending high poloidal beta scenarios on DIII-D towards a steady-state fusion reactor and impact of energetic particles. United States. https://doi.org/10.1088/1741-4326/abaf33
Huang, J., Garofalo, A. M., Qian, J. P., Gong, X. Z., Ding, S. Y., Varela, J., Chen, J. L., Guo, W. F., Li, K., Wu, M. Q., Pan, C. K., Ren, Q., Zhang, B., Lao, L. L., Holcomb, C. T., McClenaghan, J., Weisberg, D., Chan, V., Hyatt, A., Hu, W. H., Li, G. Q., Ferron, J., McKee, G., Pinsker, R. I., Rhodes, T., Staebler, G. M., Spong, D., and Yan, Z.. Wed . "Progress in extending high poloidal beta scenarios on DIII-D towards a steady-state fusion reactor and impact of energetic particles". United States. https://doi.org/10.1088/1741-4326/abaf33. https://www.osti.gov/servlets/purl/1666382.
@article{osti_1666382,
title = {Progress in extending high poloidal beta scenarios on DIII-D towards a steady-state fusion reactor and impact of energetic particles},
author = {Huang, J. and Garofalo, A. M. and Qian, J. P. and Gong, X. Z. and Ding, S. Y. and Varela, J. and Chen, J. L. and Guo, W. F. and Li, K. and Wu, M. Q. and Pan, C. K. and Ren, Q. and Zhang, B. and Lao, L. L. and Holcomb, C. T. and McClenaghan, J. and Weisberg, D. and Chan, V. and Hyatt, A. and Hu, W. H. and Li, G. Q. and Ferron, J. and McKee, G. and Pinsker, R. I. and Rhodes, T. and Staebler, G. M. and Spong, D. and Yan, Z.},
abstractNote = {To prepare for steady-state operation of future fusion reactors (e.g. the International Thermonuclear Experimental Reactor and China Fusion Engineering Test Reactor (CFETR)), experiments on DIII-D have extended the high poloidal beta (βP) scenario to reactor-relevant edge safety factor q95 ~ 6.0, while maintaining a large-radius internal transport barrier (ITB) using negative magnetic shear. Excellent energy confinement quality (H98y2 > 1.5) is sustained at high normalized beta (βN ~ 3.5). This high-performance ITB state with Greenwald density fraction near 100% and qmin ≥ 3 is achieved with toroidal plasma rotation Vtor ~ 0 at ρ ≥ 0.6. This is a key result for reactors expected to have low Vtor. At high βP (≥1.9), large Shafranov shift can stabilize turbulence leading to a high confinement state with a low pedestal and an ITB. At lower βP (<1.9), negative magnetic shear in the plasma core contributes to turbulence suppression and can compensate for reduced Shafranov shift to continue to access a large-radius ITB and excellent confinement with low Vtor, consistent with the results of gyrofluid transport simulations. These high-βP cases are characterized by weak/no Alfvén eigenmodes (a.e.) and classical fast-ion transport. At high density, the fast-ion deceleration time decreases and Δβfast is lower; these reduce a.e. drive. The reverse-shear Alfvén eigenmodes are weaker or stable because the negative magnetic shear region is located at higher radius, away from the peaked fast-ion profile. Resistive wall modes can be a limitation at simultaneous high βN, low internal inductance, and low rotation. Analysis suggests that additional off-axis external current drive could provide a more stable path at reduced q95. Based on a DIII-D high-βP plasma with large-radius ITB, two scenarios are proposed for CFETR Q = 5 steady-state operation with ~1 GW fusion power: a lower-${l_i}{\text{ }}$ (${l_i}$ ~ 0.66) and a higher-${l_i}$ (${l_i}$ ~ 0.75) case. Using a Landau closure model, multiple energetic particle (EP) effects on the a.e. stability are analyzed modifying the growth rate of the a.e.s triggered by the neutral-beam-injection EPs and alpha particles, although the stabilizing/destabilizing effect is weak for the cases analyzed. The stabilizing effects of the combined EP species β, energy, and density profile in CFETR need further investigation.},
doi = {10.1088/1741-4326/abaf33},
journal = {Nuclear Fusion},
number = 12,
volume = 60,
place = {United States},
year = {2020},
month = {9}
}

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