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Research Supported by. Profile Comparisons from the MAST/NSTX Power Threshold Identity Experiment. Rajesh Maingi Oak Ridge National Laboratory Hendrik Meyer UKAEA Fusion And the NSTX and MAST Teams NSTX Physics Meeting March 8, 2004 Princeton, NJ.

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Profile Comparisons from the MAST/NSTX Power Threshold Identity Experiment

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Profile comparisons from the mast nstx power threshold identity experiment

Research

Supported by

Profile Comparisons from the MAST/NSTX Power Threshold Identity Experiment

Rajesh Maingi

Oak Ridge National Laboratory

Hendrik Meyer

UKAEA Fusion

And the NSTX and MAST Teams

NSTX Physics Meeting

March 8, 2004

Princeton, NJ

Page 1


Profile comparisons from the mast nstx power threshold identity experiment

NSTX and MAST save similar plasma size but MAST vacuum vessel larger and outer walls further away

Vpl/VVV ~ 35-40%

NSTX

Vpl/VVV ~ 6-10%

MAST

Passive stabilizing

plates

Page 2


First detailed mast nstx identity experiment has been nearly completed

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)

Page 3


Dithery h mode in cdnd near p lh in mast

Dithery H-mode in CDND near PLH in MAST

0.5

0.0

1.0

0.0

0.4

0.0

0.0

Ip [MA]

---- 8842 ---- 8851

---- 8848 ---- 8852

PNBI [MW]

PLH

ne [1019 m-3]

Type III ELMs

Da[au]

dithers

0.0 0.1 Time[s] 0.2 0.3

Page 4


Nstx dithers not as periodic as mast cdnd near p lh

NSTX dithers not as ‘periodic’ as MAST (CDND near PLH)

“firm” L-H

“dithers”

Page 5


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)

NSTX #111378 343msec

MAST #8851 300msec

Z (m)

Z (m)

R (m)

R (m)

CDND Shapes were reasonably well matched, although NSTX shape (under rtEFIT) was a little larger

Double-null

Drsep<1mm

(“CDND”)

NSTX vac. ves.

Double-null

Drsep<1mm

(“CDND”)

NSTX vac. ves.

Page 6


Profile comparisons from the mast nstx power threshold identity experiment

NSTX ne profile more peaked and Te profile broader early

R [m]

R [m]

R [m]

yN

yN

yN

Page 7


Profile comparisons from the mast nstx power threshold identity experiment

NSTX ne (Te) lower(higher) later in H-mode phase

R [m]

R [m]

R [m]

yN

yN

yN

Page 8


Clear h mode transition in ldnd near p lh in mast

Clear H-mode Transition in LDND near PLH in MAST

0.4

0.0

2.0

0.0

0.6

0.0

0.0

ne [1019 m-3]

PLH

PNBI [MW]

Ip [MA]

---- 8856

---- 8857

---- 8859

Da[au]

L-H (ELM-free)

L-H (ELMy)

0.0 0.1 Time[s] 0.2 0.3 0.4

Page 9


No transition observed in ldnd in nstx too low density or mhd at nbi turn on

No transition observed in LDND in NSTX (too low density or MHD at NBI turn-on?)

(Reconstructed)

(no H-mode)

Sawteeth

Page 10


Nstx ldnd shape a little larger than mast magnetic balance drsep scan possible with rtefit

NSTX #111383 391msec (NBI 1.1 MW)

MAST #8859 280 msec (NBI 1.4 MW)

NSTX #111381 301msec

NSTX #111380 301msec

Z(m)

Z(m)

R(m)

R(m)

NSTX LDND shape a little larger than MASTMagnetic balance (drsep) scan possible with rtEFIT

Single-null

Drsep~10mm

(“LDND”)

NSTX vac. ves.

Single-null

Drsep~+/- 3mm

(“LDND”,”UDND”)

NSTX vac. ves.

Page 11


Profile comparisons from the mast nstx power threshold identity experiment

NSTX never achieved H-mode in LDND, but maybe needed a little more power or higher density?

R [m]

R [m]

R [m]

yN

yN

yN

Page 12


Summary and future work

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…

Page 13


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