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ELM Stability Dependence on d

NSTX. Supported by. ELM Stability Dependence on d. College W&M Colorado Sch Mines Columbia U Comp-X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U Old Dominion U ORNL PPPL PSI Princeton U Purdue U SNL Think Tank, Inc. UC Davis

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ELM Stability Dependence on d

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  1. NSTX Supported by ELM Stability Dependence on d College W&M Colorado Sch Mines Columbia U Comp-X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U Old Dominion U ORNL PPPL PSI Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Maryland U Rochester U Washington U Wisconsin A. Sontag1, J. Manickam2,T. Osborne3, P. Snyder3, R. Maingi1, 1) Oak Ridge National Laboratory 2) Princeton Plasma Physics Laboratory 3) General Atomics Culham Sci Ctr U St. Andrews York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Hebrew U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST POSTECH ASIPP ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep U Quebec

  2. Observed NSTX ELM Stability Not Consistent with ELITE Calculations 1.2 0.8 0.4 0.1 Edge current [(jmax+jsep)/2<j>] 3 4 5 6 7 8 Normalized Pressure Gradient () Dependence of pedestal pressure limit in major radius at fixed minor radius NSTX peeling-ballooning stability as calculated by ELITE for a discharge with Type I ELMs • ELITE indicates NSTX should be P-B stable • ELMs observed even though g/(w*/2) << 1 • nearer to peeling boundary • farther from ballooning boundary • PEST indicates ballooning may be important • Reduced d can increase ballooning instability drive • high-d opens up 2nd stability at low A

  3. PEST Calculations Indicate dlower Determines n = 1 Stability • dupper scanned at fixed dlower • Peak stable bN increases with increasing dlower 10 dlower = 0.3 dlower = 0.4 dlower = 0.2 5 bN 0 0 0.25 0.5 dupper

  4. Ballooning stability roughly proportional to average d 10 dlower = 0.3 dlower = 0.4 dlower = 0.2 5 bN 0 0 0.25 0.5 dupper

  5. Use 132721 as Template Shot • Original shot uses Li and has low-rotation disruption • Eliminate Li and increase NBI power to reach ELMy regime

  6. Wide Range of ds Accessible • ISOLVER modeling using 132721 as starting point • Fix PF1s & 2s, PCS control of PF3s & PF5 • Aspect ratio also varying

  7. XP Goal: Create Reduced d Plasmas with Increased Ballooning Drive • Establish reference discharge (5 shots) • Reload 132721: Ip = 0.8 MA, Bt = 0.45 T, drsep = -3cm • no Li, PNBI = 4 MW • Reduce dupper at fixed dlower • will possibly need to adjust NBI power to remain in ELMy regime • case 1, dupper = 0.17, dlower = 0.37 (5 shots) • case 6, dupper = 0.09, dlower = 0.35 (5 shots) • Reduce dlowerand dupper to make low davg shape • case 3, dupper = 0.2, dlower = 0.26 (5 shots) • case 2, dupper = 0.1, dlower = 0.2 (5 shots) • Increase dupper at fixed dlower • case 5, dupper = 0.32, dlower = 0.35 (5 shots)

  8. XP Goal: Create Reduced d Plasmas with Increased Ballooning Drive • Increase dlower at fixed dupper • case 4, dupper = 0.23, dlower = 0.47 (5 shots) • Reduce dupper at (high) fixed dlower • reduce dupper from case 4 (5 shots) • 40 shots total • in priority order • lowest-d most likely to have MHD issues

  9. Duration & Required Diagnostics • XP could be performed in 1 extended day • Required diagnostics • filterscopes • CHERS-toroidal • Thomson scattering • EFIT • Da • Desired diagnostics • edge reflectometer • two color USXR • CHERS-poloidal

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