DCPP Ak055HSQ m ,1= n 6=

4505190501#sm 0023.61=t

0.1- 5.0- 0.0 5.0 0.1)m( R

0.1-

5.0-

0.0

5.0

0.1

Z (m

)

T e )Ve(

002

092

183

274

265

356

447

438

529

6101

7011

01 21 41 61 81 02)sm( emit

02

4

6

8

01

2141

mod

e am

plitu

de (G

auss

)

6=n5=n7=n8=n

8 10 12 14 16 18 20 220

200

400

600

8 10 12 14 16 18 20 2202x1012

6x1012

1x1013

8 10 12 14 16 18 20 220

12.5

25

8 10 12 14 16 18 20 22-10-505

10

PPCD

shot 2005/9/2 52

0.0 0.2 0.4 0.6 0.8 1.0r/a

0

500

1000

1500Te (eV)

shot 2005/9/2 86

0.0 0.2 0.4 0.6 0.8 1.0r/a

0

500

1000

1500Te (eV)

Plasma Current

Density

Magnetic Fluctuations

30-s

ep-2

005

-1.0 -0.5 0.0 0.5 1.0time relative to sawtooth crash (ms)

0

600

1000

1400 r/ a = 0.0r/ a = 0.19r/ a = 0.37r/ a = 0.55

0.0 0.2 0.4 0.6 0.8 1.0r/ a

0

200

400

600

800

1000

r/ a ~ 0.8(line-integrated)

200

400

800

1200

30-s

ep-2

005

numbers are time relativeto sawtooth crash(all data 0.1 ms averaged)

-0.50

0.0

+0.25

+0.50

+0.95

200400600800

200400600800

1000

r/a = 0.0 r/a = 0.37

r/a = 0.55 r/a = 0.75Loca

lized

tem

pera

ture

(eV

)

time (ms)13 14 15 16 17 14 15 16 17

m=0 burst

m=0 burst m=0 burst

m=0 burst

0

-10

-20

0

-10

-20

0

-10

-20

0

-10

-20

Time relative to event (ms)-0.5

V/m

V/m

V/m

V/m

0.0 +0.5

r/a=0.92

r/a=0.88

r/a=0.85

r/a=0.81

<v x b>||ηJ|| - E||

MHD Dynamo in the edge balancesOhm’s law at some radii but isinsignifigant at others

Overview of Physics Advances in MSTD. Craig1,2, A.F. Almagri1,2, J.K. Anderson1, F. Bonomo3, D.L. Brower4, B.E. Chapman1, S.H. Choi1,2, D.J. Clayton1, H.D. Cummings1, B.H. Deng4, D.J. Den Hartog1,2, W.X. Ding4, D.A. Ennis1,2, G. Fiksel1,2, P. Franz3,

S. Gangadhara1,2, M. Gobbin3, J.A. Goetz1, B. Hudson1, R.M. Magee1, L. Marrelli3, P. Martin3, V.V. Mirnov1,2, R. O’Connell1, P. Piovesan3, S.C. Prager1,2, J.A. Reusch1, J.S. Sarff1,2, G. Spizzo3

MHD and Hall Dynamo

1University of Wisconsin - Madison, 2Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, 3Consorzio RFX - Associazione Euratom - ENEA Padova, Italy, 4University of California - Los Angeles

0.0 0.2 0.4 0.6 0.8 1.0r/a

0.2 ms before crash

at crash

0

100

200

300

400

500

Te (e

V)

Edge Parallel Electric Field

Quasi-Single Helicity

Ion Heating

R = 1.5 ma = 0.52 mIp = 0.2-0.6 MAne ~ 1019 m-3

Te = 0.1-1.5 keVτE = 1-10 msβtot ~ <p>/B2(a) = 5-15%

The Madison Symmetric Torus

Reversed Field PinchMagnetic Topology

B

26 28 30 32time (ms)

-0.3

-0.2

-0.1

0.0

0.1

0.2

impa

ct p

aram

eter

(m)

SXR Tomography

t = 25.5ms

-0.4 -0.2 0.0 0.2 0.4R (m)

-0.4

-0.2

0.0

0.2

0.4

Z (m

)

t = 31.5ms

-0.4 -0.2 0.0 0.2 0.4R (m)

-0.4

-0.2

0.0

0.2

0.4

Z (m

)

ABSTRACTMST continues to be a fruitful device for plasma physics, particularly for studies ofmagnetic fluctuations and their effect on transport, the current profile, and ion heating.Multi-point Thomson scattering measurements of the electron temperature profilehighlight the dramatic improvement in electron energy confinement during periods ofreduced fluctuations with current profile control and the equally dramatic degradation ofconfinement during increased fluctuations at a sawtooth crash. In quasi-single helicityplasmas (where one magnetic mode dominates the spectrum) double filter SXRtomography has been used to infer temperature profiles and observe an enhancement oftemperature inside the dominant island. Hard X-Ray measurements also showevidence for generation of a confined high energy population when a large islandis present. The current profile is strongly modified by both single and two-fluid effectsarising from magnetic fluctuations. Fast Charge Exchange RecombinationSpectroscopy measurements of velocity fluctuations yield information on the MHDdynamo <v x b> and fast FIR Faraday rotation measurements of current densityfluctuations yield information on the Hall dynamo <j x b>/en. Both are important inbalancing Ohm’s law. The current density fluctuations also induce a significant non-ambipolar charge flux during reconnection events. Ion heating accompanies bursts ofmagnetic fluctuations and is measured to be a global effect, present at all radii during asawtooth crash. Spatially non-uniform features can exist, however, when edge resonantmodes burst during periods of improved confinement. Here, a more edge localizedheating is measured. Magnetic fluctuations which grow in time cause magneticreconnection in MST. Measurements have also been made of the origin of impulsivereconnection, particularly from m=0 modes, and the importance of multi-sitereconnection for obtaining the strongest effects of fluctuations on the plasma.

This work is supported by U.S.D.O.E. and the N.S.F.

Electron Confinement

0.0 0.2 0.4 0.6 0.8r/a

0

1

2

3

4m=1, n=6m=1, n=7m=1, n=8m=1, n=9m=1, n=10m=1, n=11m=1, n=12

6 7 8 9 10 11 12n Mode Number (m=1)

r/a=0.55

e

(m2/s)

r/a r/a

PPCDStandard

1

10

100

1000

0 01 1

ts

ts

m=0 fluctuation amplitude

Heating is more edge localized duringsmall events where m=0 dominates

Ti (e

V)

Ti (e

V)

Ion heating during a sawtooth crash appears at all radii

power balance

Stochasticity and energy transport arereduced in PPCD

Measured thermal diffusivity is comparableto calculated one assuming transport isdominated by stochastic magnetic field:

Stochastic transport does not have to be large

χst = vth Dm

PPCD = Pulsed Poloidal Current Drive

Edge inductive electric fieldis modified to support currentin the outer part of plasma

Magnetic fluctuations arereduced and confinementimproves dramatically

During a sawtooth crash,magnetic fluctuationsare large and cause rapidenergy loss

-2

0

2

4

6

8

10

<vθ

b r>

)retem/stloV(

~~

0.00

0.20

0.15

0.10

0.05

-0.05

-0.100.0 0.2 0.4 0.6 0.8 1.0

n=6

910

7 8

q

r/a

Edge Modes (m=0; n=1,2,…)

Core Modes(m=1; n=6,7,…)

j || - E || = ⟨ ˜ v × ˜ B ⟩|| −1

ene⟨ ˜ j × ˜ B ⟩||η

Fluc

tuat

ing

Polo

idal

Vel

ocity

(km

/s)

Localized v and spatial profile of MHD dynamo are being measured

Hall dynamo is important at sawtooth crash in core and edge60

40

20

0

-2 -1 0 1 2Time relative to event (ms)

E// <δJx δB>// /ne

V/m

core

-0.5 0.0 0.5Time relative to event (ms)

-10

-5

0

5

10

15

20

V/m

<δJx δB>// /ne

edge

MHD Dynamo Hall Dynamo

60

40

20

0

V/m

0.80.4r/a

< δJ xδB>// /ne

0.0

Core

0.80 0.85 0.90 0.95 1.000

5

10

15

V/m

r/a

< δJ xδB>// /ne

EdgeHall dynamo is localized to mode resonant surfaces

1,6 resonance

q=0

Current fluctuations that produceHall dynamo also produce non-ambipolar charge flux

HXR emission is observed in some QSH periodsHXR emission is brightest when SXRtomography shows strong island also

Secondary mode amplitudes matter

Very hot islands can formin QSH with PPCD athigh plasma current

m=1, n=6m=0, n=1

Storedmagnetic

energy (kJ)

Toroidalflux (Wb)

Ti (eV)

Modeamplitudes

(G)

Multi-mode events give the strongest effectsof fluctuations on the plasma

-0.6 -0.4 -0.2 0.0 0.2time (ms)

-10

0

10

20

30

40

γ τ A

(x 1

0-3)

Measured MHD linear drive term

Instantaneous growth ratesfor both cases are similar

-2 -1 0 1 2time (ms)

Gau

ss

0

50

100

150

200

250

300stable mode (0,1)

offset

-1.0 -0.5 0.0 0.5 1.0time (ms)

0

60

50

40

30

20

10

Gau

ss

unstable mode (0,1)

offset

tesl

a2/s

ec

-0.1

0.0

0.1

0.2

0.3

0.4

-0.10 -0.05 0.00 0.05 0.10time (ms)

linear drive > 0unstable

(spontaneous)

tesl

a2/s

ec

-0.20

-0.15

-0.10

-0.05

0.00

0.05

-1.0 -0.5 0.0 0.5 1.0time (ms)

linear drive < 0stable

(driven)

( ) ndissipationonlinearCCt

+++⋅××∇=∂

∂..bBv

b *k0k

2k

Impulsive Reconnectionsawtooth crash m=0 burst

Impulsive reconnection occurs both for stable and unstable (nonlinearly driven) modes