profile comparisons from the mast/nstx power threshold identity experiment
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R. Maingi, ITPA NSTX/MAST talk 3_04Page 1
Rajesh MaingiOak Ridge National Laboratory
Hendrik MeyerUKAEA Fusion
And the NSTX and MAST Teams
NSTX Physics MeetingMarch 8, 2004Princeton, NJ
Profile Comparisons from the MAST/NSTX Power Threshold Identity Experiment
ResearchSupported by
R. Maingi, ITPA NSTX/MAST talk 3_04Page 2
NSTX and MAST save similar plasma size but MAST vacuum vessel larger and outer walls further away
Passive stabilizing plates
Vpl/VVV ~ 35-40%MAST
NSTX Vpl/VVV ~ 6-10%
R. Maingi, ITPA NSTX/MAST talk 3_04Page 3
First Detailed MAST/NSTX Identity Experiment Has Been (Nearly) Completed!
Goals:
compare L-H power threshold in same CDND (double-null with drsep < 3mm) shape with same Ip, Bt, density, inner-wall midplane fueling location, etc.
determine if PLH lowest with drsep=0 (go to +/- 10 mm)
Results:
CDND NBI power very similar near LH transition (~300-350 kW); need to compute PLOSS
LDND (DN with drsep ~ 10 mm, downward) had higher PLH > 1.7 MW
NSTX shape was a little bigger, and was developed with rtEFIT control (needs only a little more development)
R. Maingi, ITPA NSTX/MAST talk 3_04Page 40.0 0.1 Time[s] 0.2 0.3
Dithery H-mode in CDND near PLH in MAST
Ip [MA]
PNBI [MW]
ne [1019 m-3]
D [au]
PLH
0.5
0.01.0
0.00.4
0.0
0.0
---- 8842 ---- 8851---- 8848 ---- 8852
Type III ELMs
dithers
R. Maingi, ITPA NSTX/MAST talk 3_04Page 5
NSTX dithers not as ‘periodic’ as MAST (CDND near PLH)
“dithers”
“firm” L-H
R. Maingi, ITPA NSTX/MAST talk 3_04Page 6
CDND Shapes were reasonably well matched, although NSTX shape (under rtEFIT) was a little larger
NSTX #111378 277msec (NBI 700 kW)MAST #8851 200msec (NBI 580 kW)
R (m)
Z (m)
NSTX #111378 343msecMAST #8851 300msec
Z (m)
R (m)
Double-nullr
sep<1mm(“CDND”)NSTX vac. ves.
Double-nullr
sep<1mm(“CDND”)NSTX vac. ves.
R. Maingi, ITPA NSTX/MAST talk 3_04Page 7
NSTX ne profile more peaked and Te profile broader early
R [m] R [m] R [m]
R. Maingi, ITPA NSTX/MAST talk 3_04Page 8
NSTX ne (Te) lower(higher) later in H-mode phase
R [m]R [m]R [m]
R. Maingi, ITPA NSTX/MAST talk 3_04Page 90.0 0.1 Time[s] 0.2 0.3 0.4
Clear H-mode Transition in LDND near PLH in MAST
Ip [MA]
PNBI [MW]
ne [1019 m-3]
D [au]
PLH
0.4
0.02.0
0.00.6
0.0
0.0
---- 8856---- 8857---- 8859
L-H (ELM-free)L-H (ELMy)
R. Maingi, ITPA NSTX/MAST talk 3_04Page 10
No transition observed in LDND in NSTX (too low density or MHD at NBI turn-on?)
(Reconstructed)
Sawteeth
(no H-mode)
R. Maingi, ITPA NSTX/MAST talk 3_04Page 11
NSTX LDND shape a little larger than MASTMagnetic balance (drsep) scan possible with rtEFIT
NSTX #111381 301msecNSTX #111380 301msec
R(m)
Z(m)
NSTX #111383 391msec (NBI 1.1 MW)MAST #8859 280 msec (NBI 1.4 MW)
R(m)
Z(m)
Single-nullr
sep~10mm(“LDND”)NSTX vac. ves.
Single-nullr
sep~+/- 3mm(“LDND”,”UDND”)NSTX vac. ves.
R. Maingi, ITPA NSTX/MAST talk 3_04Page 12
NSTX never achieved H-mode in LDND, but maybe needed a little more power or higher density?
R [m]R [m]R [m]
R. Maingi, ITPA NSTX/MAST talk 3_04Page 13
Summary and Future Work
First joint NSTX/MAST experiment was a good first step toward the proposed 3-way NSTX/MAST/DIII-D collaboration on the effect of aspect ratio on pedestal
CDND power threshold was remarkably similar in terms of NBI power -> wall proximity does not play a big role in these conditions?!
Higher power CDND discharge had type IIII ELMs in MAST but largely ELM-free in NSTX
Need more LDND data from NSTX (w/edge rotation data…)
Need to work out issues related to mapping of profiles inside and outside of magnetic axis
Need better comparison shots well in H-mode, at higher Ip…
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