XP450: Differention Between ELM Types on NSTX Goals: 1) Repeat ELM types with different diagnostic configurations 2) Examine details of type V ELMs

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XP450 Differention Between ELM Types on
NSTXGoals 1) Repeat ELM types with different
diagnostic configurations2) Examine details of
type V ELMs
R. Maingi, K. Tritz, E. Fredrickson, C.
Bush NSTX XP Review June 18, 2004 Princeton,
NJ
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Wide variety of ELMS observed in NSTX
Da au
Type I - Mid DWMHD Magnetic signature No
pre-cursor Type III - Small DWMHD Magnetic
signature And high frequency pre-cursor NEW,
type V Tiny(?) DWMHD Magnetic signature No
pre-cursor Mixed Type V Giant ELM (couples
to core mode?) Large DWMHD
WMHD kJ
Sabbagh
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Density ramps throughout discharge and affects
ELMs modestly
Da au
39 torr-l/s 14 torr-l/s 9
torr-l/s 3 torr-l/s
Time of constant NBI power with no locked
mode signature
Flow too low Dithers only
Double-null
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Larger ELMs observed at lower density
DW/W0
all ELMs
DW/Wped
Double-null
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Fueling (density) strongly affects ELMs in
single-null
Da au
Type V
39 torr-l/s 14 torr-l/s 11
torr-l/s
Type V
Giant
Flow too low Dithers only
Single-null
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Small ELMs in high performance discharge (Type V)
Ip MA
PNBI/10 MW
???????
USXR au
ne 1019 m-3
D? au
D? au
torr-l/s
SNBI
WMHD kJ
dNe/dt
108729
WMHD10 MJ
H89P
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Small ELMs observed as a 20-30 enhancement of
entire Da profile
D? au
Type V ELMs
Soukhanovskii
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Filament-like structure (n1) observed prior to
Ultra-soft X-ray perturbation and Divertor Da
Increase
Menard
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Type V ELMs usually originate in lower divertor
region in Ultra-soft X-ray Diagnostic
Inboard Center Outboard Midplane
Lower Divertor
Tritz, Stutman
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Run Plan Part I Reproduce discharges with
different ELM types and switch diagnostic
configurations

• Restore112503 (Ip800 kA, Bt4.5 kG, PNBI6 MW)
  which had type V and several type I ELMs and
  cycle through diagnostic changes in repeat shots
  (5 shots)
• Change USXR filters from Be100, Be5, Ti03, and
  mixed
• Rotate fast divertor camera from no
  filter/Da/C-III
• Change GPI timing to catch ELMs at fastest rate
• Run divertor Langmuir probe at 0 voltage to look
  for SOL current
• Change dwell depth on edge reciprocating probe to
  look for ELM radial extent into SOL (if
  available)
• Repeat 112159 (Ip800 kA, Bt4.5 kG, PNBI2 MW,
  with PF1B) which had type III ELMs and cycle
  through diagnostic changes in repeat shots (5
  shots)

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Reference LSN has both type V and type I ELMs
PNBI/10 MW
Da au
H89
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Reference LSN with PF1B has type III ELMs
(proximity to power threshold, magnetic
pre-cursor oscillation)
PNBI/10 MW
Da au
H89
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Run Plan Part II Look at correlation between
type V ELMs and center stack midplane puffer

• Restore 112506 (Ip800 kA, Bt4.5 kG, PNBI3 MW)
  which had type V only, and drop fueling rate to
  look for threshold for type V ELMs (2-5 shots)
• Decision point If minimum fueling rate needed
  for L-H transition is above the threshold for
  type V ELMs, then consider (a) using the early
  H-mode discharges which did not require center
  stack fueling (112550), and then add the fueling
  in small bits until type V ELMs observed, or (b)
  use the successful shoulder fueling scenarios
  (112771) and add center stack in small amount to
  try to trigger type V ELMs. (2-5 shots)
• Change q95 from step III in LSN (higher Ip 1
  MA, maybe Bt 0.4 T) to see if origin of USXR
  perturbation moves away from the lower divertor
  region (3 shots)
• Compare ELMs in DN with LSN from step 1, i.e.
  re-run 112525 (DN), and cycle through filters if
  desire (5 shots)

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Fueling with shoulder injector produced ELM-free
or Type I, but not Type V ELMs in near DND
(drsep-0.7cm)
Center stack midplane fueling
Center stack shoulder fueling
PNBI/10 MW
PNBI/10 MW
Da au
Da au
H89
H89
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Early H-mode with no center stack fueling showed
no Type V ELMs
PNBI/10 MW
Da au
H89
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Reference DN comparison to LSN shows different
ELMs (not type V - maybe Type I?)
PNBI/10 MW
Da au
H89
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Backup
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Type V ELMs are occasionally observed in DND
PNBI/10 MW
Da au
H89
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Type V ELMs sometimes disappear spontaneously in
standard LSN fiducials
PNBI/10 MW
Da au
H89
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Envelope of ELM size decreases with frequency
Double-null