nstx xp1031: mhd/elm stability vs. thermoelectric j, edge j, and collisionality -nstx physics mtg....

NSTX XP1031: MHD/ELM stability vs. thermoelectric J, edge J, and collisionality -NSTX Physics Mtg. 6/28/10 - S.A. Sabbagh, et al.

S.A. Sabbagh1, T.E. Evans2, L.E. Zakharov3, J-W. Ahn4, J. Canik4, R. Maingi4, J.W. Berkery1, J.M. Bialek1, S. Gerhardt3,

J-K. Park3, Y-S. Park1, H. Takahashi3, K. Tritz5, et al.

XP1031: MHD/ELM stability dependence on thermoelectric J, edge J, and

collisionality

Supported by

Columbia UComp-X

General AtomicsINEL

Johns Hopkins ULANLLLNL

LodestarMIT

Nova PhotonicsNYU

ORNLPPPL

PSISNL

UC DavisUC Irvine

UCLAUCSD

U MarylandU New Mexico

U RochesterU Washington

U WisconsinCulham Sci Ctr

Hiroshima UHIST

Kyushu Tokai UNiigata U

Tsukuba UU Tokyo

JAERIIoffe Inst

TRINITIKBSI

KAISTENEA, Frascati

CEA, CadaracheIPP, Jülich

IPP, GarchingU Quebec

NSTX Physics MeetingJune 28th, 2010

Princeton Plasma Physics Laboratory

1Department of Applied Physics, Columbia University2General Atomics

3Princeton Plasma Physics Laboratory4Oak Ridge National Laboratory

5Johns Hopkins University

V1.1


Continuation of XP1031 last week: MHD/ELM stability dependence on thermoelectric J, edge J,

• Goals/Approach Test expectations ELM stability theory considering changes to edge toroidal

current density, field-aligned thermoelectric current, and collisionality• 1) Generate target• 2) Vary TE current connection length at fixed 3D field (Vary x-point height; DRSEP)• 3) Vary 3D field amplitude• 4) Vary toroidal current density near the edge• 5) Vary collisionality with LLD

• Data from last week Ran many shots on list (except reduced ); need to examine data in detail

• X-point height and DRSEP varied separately (tricky for operators early on) ELMs change with variation – much detail to sort out here

• Target reproduced with ELMs induced by 3D field• 50 Hz n = 3 field primarily used, DC field tried but led to rotation issues• Scrape-off layer currents detail measured by LLD shunt tiles / Langmuir probe arrays

e.g. n = 1 clearly seen during initial part of ELM, changing to n = even

• Evidence of ELM stabilization when positive edge current applied (constant B t)


XP1031: MHD/ELM stability dependence on thermoelectric J, edge J, and collisionality – shot plan

Task Number of Shots1) Generate target

A) Preferable is LSN ELMing plasma target (138129, or 137564), suitable for +/- Z movement 4

- Add 3D field (use shot 138132); then try DC field - choose 3D field magnitude based on XP818

- Plasma control: suggest (i) PF3-boundary position (squareness), (ii) DRSEP, (option: use outer SP control)

2) Vary TE current connection length at fixed 3D field

A) LSN: (change PF3-boundary to vary Z, vary DRSEP independently if possible) (three Z positions) 6

B) DND: 1

C) USN: (two Z positions) - (contrast grad(B) drift direction / effect to condition (2A)) 4

3) Vary 3D field amplitude

A) near marginal condition from (2), still ELMing, decrease n = 3 field until ELMs go away 3

B) near marginal condition from (2), not ELMing, increase n = 3 field until ELMs return 3

4) Vary toroidal current density near the edge

A) near marginal condition from (2), still ELMing, decrease Ip with slow ramp, attempt ELM stabilization 3

B) near marginal condition from (2), not ELMing, increase Ip with slow ramp, for ELM destabilization 3

C) redo (A) and (B) with TF ramp up/down to keep q approximately fixed 4

5) Vary collisionality with LLD

A) Rerun successful conditions above at reduced collisionality with LLD 16

Total: 31; 16

V1.3

completed

completed


• Profile comparison (ne, Te vs. psiN) for shots with edge current changed

One XP1031 scan examined the effect of toroidal edge current change on ELM stability

0.0 0.5 1.0 1.5 2.0R(m)

-2

-1

0

1

2

-2

-1

0

1

2

Z(m

)

from \EFIT02, Shot 138830, time=697ms

NSTXo00()------ ----- -----------

0.0 0.2 0.4 0.6 0.8 1.0Ψ/Ψa

02468

10

n e (1

019m-3 )

138830 @ 0.698s138833 @ 0.698s138836 @ 0.698

Constant Ip

Decreased edge J

Increased edge J

Constant Ip

Decreased edge J

Increased edge J

/N

0.0 0.2 0.4 0.6 0.8 1.0Ψ/Ψa

0.00.40.81.21.62.0

T e(ke

V)

138830 @ 0.698s138833 @ 0.698s138836 @ 0.698

/N

138830t = 0.697s


ELMs generated when 3D field was applied

no 3D fieldw/ 3D field

138129138132


XP1031: Evidence of ELM stabilization with positive current ramp + 3D field during ELMing phase

ENGINEERING::IP2

800000850000900000950000

ampe

res

Normalized toroidal beta

012345

-

Plasma to limiter gap (lower)

00.050.100.150.200.25

m

Upper div. D-alpha

00.020.040.060.080.10

volts

-1*raw_of(\USXR::USXR_HUP_00:RAW)

0.5 0.55 0.60 0.65 0.70 0.75 0.80seconds

-15000-14000-13000-12000-11000

nano

amps

138830138836

Shots:NSTXo00()------ ----- ------

ELM-free period(plasma in H-mode) H-L back-transition

ENGINEERING::IP2

8600008800009000009200009400009600009800001x106

ampe

res

Normalized toroidal beta

012345

-

Plasma to limiter gap (lower)

00.050.100.150.200.25

m

Upper div. D-alpha

00.020.040.060.080.10

volts

-1*raw_of(\USXR::USXR_HUP_00:RAW)

0.5 0.55 0.60 0.65 0.70 0.75 0.80seconds

-15000-14000-13000-12000-11000

nano

amps

138830138833

Shots:NSTXo00()------ ----- ------

Constant Ip and decrease edge J: similar ELMing Constant Ip and increase edge J: ELM-free period found

138830138833

138830138836


H-mode terminates in ELM-free discharge from Prad increase

ELM freeperiod

H-L back-transition, atIP ramp start,but recovers

H-mode

Densityrises, and

Prad

sharplyrises duringELM-free

period

138836

nstx xp1031: mhd/elm stability vs. thermoelectric j, edge j, and collisionality -nstx physics mtg....

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