Current Drive Experiments with OscilCurrent Drive Experiments with Oscillating Toroidal Flux in HT-7 Superconlating Toroidal Flux in HT-7 Supercon

ducting Tokamakducting Tokamak

J.S.Mao, P. Phillips1, J.R.Luo, J.Y.Zhao, Q.L.Wu, Z.W.Wu, J.G.Li, and HT-7 team

Institute of plasma Physics, Academia Sinica, Hefei, Anhui, 230031, P.R.China

1. Fusion Research Center, RLM 11-222 UT at Austin. TX 78712 USA* Support by National Natural Science Fund of China

HT-7 ASIPP

HT-7 ASIPPMOTIVATIONMOTIVATION

A crucial issue for the extension of advanced tokamak scenarios to long pulse operation is to avoid these MHD instabilities The control of the low order m / n tearing modes has attracted much research Various methods proposed to suppress the tearing modes to prevent disruptions MHD suppression was achieved using resonant magnetic perturbation (RMP) or magnetic feedback MHD suppressing has been research with new methods

Oscillating plasma current on HT-7 Tokamak Modulate plasma horizontal position Modulate LHCD Modulate IBW

HT-7 ASIPPExperimental Set-upExperimental Set-up

* The feedback control system for the HT-7 tokamak is a multi-variable feedback controller due to the strong coupling between the ohmic heating coil and vertical field coil. Input parameters: plasma current; vertical coil's current; center of the last magnetic surface as measured by the four single flux loops.

* The output parameters are the ohmic heating current and the vertical coil's current. Response time of the feedback system is limited by double copper shell to greater than 200ms.

HT-7 ASIPP

Toroidal flux was modulated by programming the ohmic heating field or by vertical field two types of experiments have been performed Involves modulating plasma current only, while the other experimental parameters are held constantModulating plasma horizontal position with the plasma current kept constant by a feedback system

Experimental Set-upExperimental Set-up

HT-7 ASIPP

0 100 200 300 400 500 t (ms)

1

03.2

01.3

0 1

-1130

0 Ip

Br

SX

Ne(

0)

E

CE

KA

a.u

.

a.

u.

1013

cm-3

a

.u.

.

(e)

(d)

(c)

(b)

(a)

Modulating plasma current only, while the other experimental parameters are held constant

Ip=114KA,

dIp/Ip=30%, f=40Hz

Negative Pulses

-dIp/dt=5.43MA/s,

+ dIp/dt =2.4MA/s,

Total radiation (Bol.)

modulated and decrease

Te(0) increased

MHD suppressed

HT-7 ASIPP

Shot No. 24230

200 300 400 500 Time (ms)

1

03.2

01.3

0 1

-1130

0

Bol

Ne(0)

SX(0)

Ip

θB~

KA

a.u

.a.

u.

a.u

.

1013

cm-3

HT-7 Tokamak

0.3 0.4 0.5 0.6 0.7

1.4

2.1

2.80.3 0.4 0.5 0.6 0.7

-0.8

-1.0

-1.20.3 0.4 0.5 0.6 0.7-0.5

-0.4

-0.30.3 0.4 0.5 0.6 0.7

90

120

150

(a.u

.)

time (sec)

(d) (a

.u.) (c)

(a.u

.) (b)

(K.A

.)

(a)

B~

rB~

363 449 534 620 706-1

1-1

1

60

140

KA

0

3

-1.0

1.0

Va.

ucm

a.u

Time (ms)

Shot N0. 34448

Ip

Vl

a1

I II

R=65cm, a=18.7cm, Bt=1.0T , Ip=60kA. Ip=60-70KA, dIp/Ip=14-20%, +dIp/dt=120MA/s, - dIp/dt=5.3MA/s, f<200Hz

HT-7 ASIPPHT-6M Tokamak

HT-7 ASIPP

rB~

B~

( II )(1)

Typical Discharge of the HT-7 Tokamak Typical Discharge of the HT-7 Tokamak with Modulation Plasma Currentwith Modulation Plasma Current

HT-7 ASIPP

Modulating plasma horizontal position with the plasma current kept constant by feedback

45165V

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0 200 400 600 800 1000 1200 1400

t (ms)

V (2.4kV)

<V> (2.4kV)

45165I

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 200 400 600 800 1000 1200 1400

t (ms)

I (6kA)

<I> (6kA)

0 .25 .50 .75 1.0 1.25 time (S)

Ip

Vp

Iv

H

SX

Ne

120KA

02.7V

02.0V

0a.u

a.u.

2.0

0

HT-7 ASIPP

0

1

2

3

4

5

6

x 10-5

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Time [msec]

Nor

mal

ized

Hor

izen

tal P

ositi

on

HT-7 XUV Image: Pulse #4516829-Dec-2001

Plasma Minor Radius Modulated a ~ 3 cm– 5 cm

The time and spatial distribution of bolometer signal with the plasma horizontal displacement modulated

Raw Data of Soft X-Ray array

HT-7 ASIPP

B~

rB~

363 449 534 620 706-1

1

-1

1

60

140

KA

0

3

-1.0

1.0

Va.

ucm

a.u

Time (ms)

Shot N0. 34448

Ip

Vl

a1

I II

Ne (r) Te(r) during TFCMNe (r) Te(r) during TFCM

450 500 550 600 650

1.2

1.4

1.6

1.8

2.0

k

time(ms)

HT-7 ASIPP

B~

rB~

363 449 534 620 706-1

1-1

1

60

140

KA

0

3

-1.0

1.0

Va.

ucm

a.u

Time (ms)

Shot N0. 34448

Ip

Vl

a1I II

Profile Changes during TFMC

0.0 0.2 0.4 0.6 0.8 1.00

40

80

120

160

200

240

j (r)

r/a

450ms 525ms 590ms 644ms

-20 -10 0 10 20 r (cm )

2.1

1.8

1.5

1.2

0.9

0.6

Ne

( 1

013cm

-3 )

0.0 0.2 0.4 0.6 0.8 1.00.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

450ms 525ms 590ms 644ms

q pr

ofile

s

r/a

HT-7 ASIPP

0 420 840 1260 1680 2100

time (ms)

B

LPI

HX

H

Ip

2.5

-2.5 4

-4 0

-11.57

-1 136

0

V

V

V

V

KA

Suppression of MHD

the edge potential

fluctuation

HX emission

Long Pules Discharge without wall condition

HT-7 ASIPP radiation（ 10eV-10keV)

MHD instability was reduced

Modulated IBW heatingModulated IBW heating

AC IBW

HT-7 ASIPP

LHCD

120 240 360 480 600 Time (ms)

.2

-.2 1.2

-1.2 3

0120

0

K AV

a.u

.a.

u.

θB~

rB~

V l

I p

MHD modulated with AC curret & AC LHCD

AC LHCD

Conclusion

HT-7 ASIPP

• The plasma equilibrium current modulated by a frequency current has been successful used in suppressing MHD perturbations effectively on the HT-7 superconducting tokamak and HT-6M tokamak

• Control of the plasma pressure profile with local modulated IBW heating can be possible to suppression MHDto suppression MHD

• Modulating and Suppression MHD by modulating LHCD

• The resonant magnetic surfaces perturbations with differThe resonant magnetic surfaces perturbations with different ways, It is difficult for the instability of the tearing ment ways, It is difficult for the instability of the tearing modes to develop in some fixed locations.odes to develop in some fixed locations.