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

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.

doi:10.1088/1741-4326/abaf33

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

Journal Article · Wed Sep 23 00:00:00 EDT 2020 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/abaf33· OSTI ID:1666382

^[1]; ^[2]; Qian, J. P. ^[3]; Gong, X. Z. ^[3]; ^[3]; ^[4]; ^[3]; ^[3]; ^[3]; ^[5]; ^[3]; Ren, Q. ^[3]; ^[3]; Lao, L. L. ^[2]; Holcomb, C. T. ^[6]; McClenaghan, J. ^[2]; ^[2]; Chan, V. ^[2]; Hyatt, A. ^[2]; ^[3] more »

Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics; General Atomics, Energy & Advanced Concepts, DIII-D
General Atomics, San Diego, CA (United States)
Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics
Univ. Carlos III de Madrid (Spain)
Shenzhen Univ. (China). Advanced Energy Research Center
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Univ. of Wisconsin, Madison, WI (United States)
Univ. of California, Los Angeles, CA (United States)
Oak Ridge Associated Univ., Oak Ridge, TN (United States)

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 (β_P) 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 (H_98y2 > 1.5) is sustained at high normalized beta (β_N ~ 3.5). This high-performance ITB state with Greenwald density fraction near 100% and q_min ≥ 3 is achieved with toroidal plasma rotation V_tor ~ 0 at ρ ≥ 0.6. This is a key result for reactors expected to have low V_tor. At high β_P (≥1.9), large Shafranov shift can stabilize turbulence leading to a high confinement state with a low pedestal and an ITB. At lower β_P (<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 V_tor, consistent with the results of gyrofluid transport simulations. These high-β_P 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 Δβ_fast 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 β_N, 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-β_P plasma with large-radius ITB, two scenarios are proposed for CFETR Q = 5 steady-state operation with ~1 GW fusion power: a lower-$$l_i$$($$l_i$$ ~ 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.

View Accepted Manuscript (DOE)

Research Organization:: General Atomics, San Diego, CA (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Univ. of California, Los Angeles, CA (United States); Univ. of Wisconsin, Madison, WI (United States)

Sponsoring Organization:: Anhui Provincial Natural Science Foundation; National Natural Science Foundation of China (NNSFC); USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: AC05-00OR22725; AC52-07NA27344; FC02-04ER54698; FG02-08ER54984; FG02-08ER54999

OSTI ID:: 1666382

Alternate ID(s):: OSTI ID: 1664598
OSTI ID: 1797656
OSTI ID: 1798020
OSTI ID: 23018696

Report Number(s):: LLNL-JRNL--812779

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 12 Vol. 60; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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