nstx sas – aps dpp ‘05 supported by office of science s.a. sabbagh 1, a.c. sontag 1, w. zhu 1,...

NSTX SAS – APS DPP ‘05

Supported byOffice ofScience

S.A. Sabbagh1, A.C. Sontag1, W. Zhu1, M.G. Bell2, R. E. Bell2, J. Bialek1, D.A. Gates2, A. H. Glasser3, B.P. LeBlanc2, F. Levinton4, J.E.

Menard2, H. Yu4, D. Battaglia5, and the NSTX Research Team

Resonant Field Amplification and Resistive Wall Mode Stability in NSTX

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

47th Annual Meeting of the Division of Plasma PhysicsAmerican Physical Society

October 24 – 28, 2005Denver, Colorado

1Department of Applied Physics, Columbia University, New York, NY2Plasma Physics Laboratory, Princeton University, Princeton, NJ

3Los Alamos National Laboratory, Los Alamos, NM4Nova Photonics, Inc., Princeton, NJ5University of Wisconsin, Madison, WI

v1.8


Wall stabilized plasmas allow RWM studies

• Operation with N/Nno-wall >

1.5 at highest N for pulse >> wall

• Past experiments showed Unstable resistive wall

mode (RWM) with toroidal mode number up to 3

Critical rotation frequency profile ~ 1/q2

Resonant field amplification (RFA) increases with increasing N

-25-20-15-10

-505

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

N

01234567

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

DCON

W

0

10

20

0.6 0.70.50.40.30.20.10.0t(s)

n=1 (no-wall)n=1 (wall)

112402

wall stabilized

core plasma rotation(x10 kHz)

New capabilities continue the study of RFA and RWM stability


Non-axisymmetric coils for advanced RWM experiments

Upper/lower RWM

Sensor Arrays

• Six coils spanning midplane n = 1 - 3 DC or AC standing

waves Toroidally propagating fields

• Experiments address RWM dynamics at marginal

stability

• using modulated n = 3 standing wave fields

Resonant field amplification

• using toroidally propagating n = 1 fields

Triggering of other MHD

• using co- vs. counter-rotating applied fields with changing frequency

Non-axisymmetric field coils(ex-vessel)


0.30 0.35 0.40 0.45 0.50 0.55t(s)

0

4

8

0

10

200

10

20

300

10

20

30

Shot 116178

0

2

4

6

0.30 0.35 0.40 0.45 0.50 0.55t(s)

0100

200

3000

100

200

3000

100

200

3000

2

4

6

Shot 116178

-1.0-0.50.00.51.0

• Modulated rotation cycles stability “anti-lock” braking of

plasma rotation

n = 1 rotates in direction of flow

n = 2 not rotating with plasma flow

n=3 standing wave field probes RWM marginal stability

Plasma rotation

I RW

M2

(kA

) B

p(n

=1

) B

p(n

=2

) B

p(n

=3

)

/2

(kH

z)|Bpu|(n=1)(G)

|Bpu|(n=2)(G)

|Bpu|(n=3)(G)

N

|Bpl|(n=1)(G)

1.0 1.2 1.4R(m)

/

2 (

kHz)

0

10

20

30

40

t(s)0.4160.4260.4360.4460.456

cyclic

R = 1.35m

Nno-wall (DCON)


growth rotationdamping

0.50 0.51 0.52 0.53 0.54t(s)

0

4

8

120

10

200

10

20

300

10

20

30

Shot 116178

0

2

4

6

0.50 0.51 0.52 0.53 0.54t(s)

0100

200

3000

100

200

3000

100

200

3000

100

200

300

Shot 116178

-10-505

10

• RWM n=1 component shows growth and rotation Growth rate: 268 s-1

Rotation rate (avg. one cycle): 48Hz

RWM possibly triggers rapidly rotating mode

• n=2 growth / phase change during n=1 damping / spin-up

Last cycle before collapse shows RWM dynamics

Bp

(n=

1)

Bp

(n=

2)

Bp

(n=

3)

Bp

(n=

1)

|Bpl|(n=1)(G)

|Bpu|(n=2)(G)

|Bpu|(n=3)(G)

N

|Bpu|(n=1)(G)

Bz

(G)

spin-up

Nno-wall (DCON)


1.E+01

1.E+02

1.E+03

1.E+04

1.E-03 1.E-02 1.E-01

RWM growth/rotation modeled with VALEN consistent with measurement

• Boozer RWM model in VALEN code Plasma rotation

• Normalized plasma torque

RWM rotation

• Calibrate code using NSTX data RWM rotation

measured near marginal stability

RWM growth rate measured when edge reduced

Unstable Stable

N ~ 4.7

N ~ 5.47

N ~ 5.61

N ~ 6.4

RW

M (

1/s

),

RW

M (

rad/

s)

10-3 10-2 10-1101

102

103

104

116178(marginalstabilityN = 5.5)

116178(unstable -

reduced )

~ plasma rotation

Solid line: RWM growth rateDashed: RWM rotation rate

measured


0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

-120 -90 -60 -30 0 30 60 90 120

RFA magnitude dependent on applied field frequency

• Applied field phased to create traveling wave in toroidal direction

• Peak in RFA shifted in the direction of plasma flow Peak near 30 Hz Expected by RWM

theory / experiment• Observed in DIII-D (H.

Reimerdes, NF 45 (2005) 368.)

RF

A m

ag

nitu

de

(n

= 1

)

Applied frequency (Hz)

Direction ofplasma flow

RFA =Bapplied

Bplasma

Counterplasma flow

Shifted peak

Single modemodel fit


Direction of applied n=1 traveling wave alters RWM stability

Field propagates with flow Field propagates against flow

Bp

n=

1(G)

Ph

ase

Bp

n=

1IR

WM(

kA)

116940 116941

0.25 0.35 0.45 0.55Time (s)

0.25 0.35 0.45 0.55Time (s)

360

240

120

0

80

60

40

20

0

1

0.5

0

-0.5

-1

• Stronger RFA with co-flow field

• RWM not destabilized

(co-flow) (counter-flow)

• Weaker RFA with counter-flow field

• Unstable RWM

LargerRFA

RWMsmaller

RFA


Unstable RWM avoided when rotation maintained

Applied field in the direction of plasma flow: RFA increases and rotation damps n=1 internal mode triggered Rigid rotor rotation profile; beta recovers

Applied field against the plasma flow: RWM grows Rapid, complete rotation and beta collapse0.0 0.2 0.4 0.6 0.8

Time (s)

0.9 1.1 1.3 1.5R (m)

40

30

20

10

0

116940 116941

Ft

(kH

z)

0.9 1.1 1.3 1.5R (m)

(applied field co-flow) (counter-flow)co-

counter

co-

counter

counter

co-

Nno-wall (DCON)

core rotation


New non-axisymmetric coils have enabled advanced RWM experiments

• Precise modification of the plasma rotation profile allows control of RWM near marginal stability

• RWM rotation near marginal stability allows comparison to theory (Boozer model)

• Resonant field amplification depends on applied field frequency and propagation with respect to plasma flow

• Direction of applied field propagation can modify RWM evolution; triggering of other MHD modes

• Plasma rotation profile control / rotation damping physics (Zhu GO3.00005 – next talk)

• Critical rotation profile for RWM stability (Sontag RP1.00021 Thurs.) Rotation on higher order rational surfaces not required for stability

nstx sas – aps dpp ‘05 supported by office of science s.a. sabbagh 1, a.c. sontag 1, w. zhu 1,...

Documents