1. Comparison of Small ELM regimes A C-MOD/MAST/NSTX Multi-machine ITPA proposal
Question:
Is the NSTX Type V ELMy H-mode the same as a high  EDA H-mode in C-MOD with individual ELMs?
Background:
C-MOD/JFT-2M similarity experiment showed the similarities between the EDA and HRS H-mode regimes
Similarities in NSTX Type V ELMy regime and HRS except 1) no QC mode and 2) clear, individual ELMs observed in NSTX
Individual ELMs observed on top of EDA H-mode as  is increased in C-MOD -> NSTX and MAST always above a threshold value?
Execution:
n*eq95and borr* at outer midplane pedestal will be matched in a common lower single-null shape with k, dand ssep (drsep)~-2cm, at several operational points
ELM characteristics and operation windows will be compared in all three machines (~ 1 day each machine)
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R. Maingi, PEP-16 proposal, C-MOD RF 2004

2. Many Different ELM types Observed in NSTX
Da [au]
WMHD [kJ]
DWMHD/WMHD~ 3-15%
Pheat >> PL-H
DWMHD/WMHD~ 1-5%
Pheat > PL-H
DWMHD /WMHD< 1%
Wide Pheat range
DWMHD /WMHD< 30%
High Pheat, bN
Large (Type I)
Mid (Type II/III)
Small (Type V)
Mixed regime
Maingi, EPS2004
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R. Maingi, PEP-16 proposal, C-MOD RF 2004

3. Pedestal n*e  1 Divides Type V and Mixed ELM regimes in NSTX
Ip: MA, Bt=0.45 T, PNBI: 2-6 MW, LSN, k=2.0, d=0.4
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R. Maingi, PEP-16 proposal, C-MOD RF 2004

4. BACKUP
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R. Maingi, PEP-16 proposal, C-MOD RF 2004

5. Small ELMs are distinct, individual perturbations with signatures on Da and Ultra-Soft X-Rays in NSTX
PNBI/10 [MW] bN

L-H
WMHD [kJ]
D [au]
USXR [au]
#108729
Maingi, NF 2004 submitted
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R. Maingi, PEP-16 proposal, C-MOD RF 2004

6. NSTX and MAST save similar plasma size but MAST vacuum vessel larger and outer walls further away
Vpl/VVV ~ 35-40%
NSTX
MAST
Vpl/VVV ~ 6-10%
Both: R ~ 0.85m, a ~ 0.6 m, R/a > 1.3
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R. Maingi, PEP-16 proposal, C-MOD RF 2004

7. n=1 pre-cursor to small ELMs propagates toroidally counter to Ip and poloidally away from X-point in NSTX
Divertor Da
Wall Bz
TOROIDAL
First sign of perturbation
Top
POLOIDAL
Bottom
Leakage location?
Menard
Tritz, JHU
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R. Maingi, PEP-16 proposal, C-MOD RF 2004