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NSTX 2010 Experimental Proposal: Peeling-Ballooning Stability Dependence on Plasma Triangularity

NSTX. Supported by. NSTX 2010 Experimental Proposal: Peeling-Ballooning Stability Dependence on Plasma Triangularity. 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

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NSTX 2010 Experimental Proposal: Peeling-Ballooning Stability Dependence on Plasma Triangularity

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  1. NSTX Supported by NSTX 2010 Experimental Proposal: Peeling-Ballooning Stability Dependence on Plasma Triangularity 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 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 Aaron Sontag, Oak Ridge National Lab FY2010 NSTX Research Forum Dec. 1-3, 2009

  2. Proposal: Alter Peeling-Ballooning Stability Boundary by Varying Plasma Triangularity 1.2 0.8 0.4 0.1 Edge current [(jmax+jsep)/2<j>] 3 4 5 6 7 8 Normalized Pressure Gradient () NSTX peeling-ballooning stability as calculated by ELITE for a discharge with Type I ELMs 10 Ballooning stability as calculated by PEST 5 bN dlower = 0.3 dlower = 0.4 dlower = 0.2 0 0 0.25 0.5 dupper NSTX peeling-ballooning stability inconsistent with ELITE calculations • ELMs observed even though g/(w*/2) << 1 PEST indicates ballooning may be important • max. stable bN roughly proportional to avg. d Reduced d can increase ballooning instability drive • high-d opens up 2nd stability at low A 2

  3. XP 942 Successfully Affected ELM Stability with dlower modification dlower decrease coincident with transition to small ELMs • drsep unchanged until well after small ELM regime (0.46 s) Further d reduction needed to approach ballooning boundary • PEST indicates n=3 still most unstable mode • shot development required going shape with decreased stability dupper scan also needed • go to higher k, Z0 > 0 plasma, or reduce outer gap 3

  4. XP Plan: Continue d scan from XP 942, independently varying dupper & dlower • Decreased d possible with increased outer gap • more modeling required for this scenario • XP 942 target was low-k (~1.9) LSN • difficult to affect dupper with large separation from control coils • dupper always slightly less than dlower • ISOLVER modeling shows more control of dupper achievable at increased-k • Use PF1AU to push/pull dupper • Fix PF1s & 2s, PCS control of PF3s & PF5 • increase k request • Vary dupper at fixed dlower • vary upper squareness request

  5. Duration & Required Diagnostics • XP could be performed in 1 day • Required diagnostics • CHERS (beam blips in HHFW-only discharges) • USXR arrays • magnetics • Thomson scattering • EFIT (w/MSE) • Da • Desired diagnostics • edge reflectometer • two color USXR

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