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ELM Working Group Discussion

ELM Working Group Discussion. Why do we need an ELM working group? multiple science areas: stability, transport, and edge convenient mechanism for gathering all interested What is the purpose of this meeting? Discuss function of this group

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ELM Working Group Discussion

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  1. ELM Working Group Discussion • Why do we need an ELM working group? • multiple science areas: stability, transport, and edge • convenient mechanism for gathering all interested • What is the purpose of this meeting? • Discuss function of this group • Discuss individual research interests for team building Page 1

  2. Proposed Functions of ELM Working Group • informal technical discussion group • improve planning of ELM-related experiments • Other goals of member? Page 2

  3. Wide variety of ELMS observed in NSTX Da [au] Type I - Mid DWMHD No magnetic pre-cursor Pheat >> PL-H Type III - Small DWMHD Low frequency pre-cursor NEW, type V Tiny(?) DWMHD Magnetic signature n=1 No clear pre-cursor Mixed Type V + ‘Giant ELM’ (couples to core mode?) Large DWMHD WMHD [kJ] Maingi, EPS2004 Page 3

  4. Characteristics of Type I and V ELMs Type I ELM large DWMHD Type I ELM WMHD [kJ] Da [au] Outflux from pedestal hd-12 [au] “Ped.” USXR “Sep” USXR Influx to SOL Or separatrix Type V ELMs hd-14 [au] 0.2-40 kHz [au] Odd-n MHD No pre-cursors Odd-n MHD 40-400 kHz [au] No clear signature Page 4

  5. WMHD [kJ] Da [au] “Ped.” USXR hd-12 [au] “Sep” USXR Odd-n MHD 0.2-40 kHz [au] Odd-n MHD ELM 40-400 kHz [au] Characteristics of Type III ELMs Little impact per each ELM Outflux from pedestal hd-14 [au] Influx to SOL Or separatrix Low frequency 2 kHz pre-cursor High frequency signature Fishbones Page 5

  6. 01 17 20 10 14 140 25 200 70 250 50 42 40 150 145 155 160 165 Type I(III, V) ELMs do (not) burn through MARFE-like region near inner X-point Inner Separatrix Outer Strike point MARFE-like region I III V • All data with 24.7ms time between frames; relative frames numbers indicated • ELMS from different shots or different time range within a shot Page 6

  7. 01 17 20 10 14 25 Type V ELM perturbation lasts for < 500msec • Top: divertor view of Type V ELM (#112503@0.398s) • Bottom: Midplane view of Type V ELM (#109063@0.598s) • (24.7ms time between frames; relative frame times indicated) Passive plate gap Inner Separatrix Outer Strike point MARFE-like region 10 20 25 13 17 30 Filaments Inner Strike Point Outer Strike point ELM growth/decay Page 7

  8. ELM analysis uses data from multiple diagnostics • Total energy drop from fast EFITs (0.25 ms) • Pedestal energy from modified tanhfit to Thomson pressure profile (20 points spatial, 60 Hz) Wped=0.92volumeEFIT  3peped • * J. Cordey, et. al., Nucl. Fusion 43 (2003) 670. Page 8

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