SUNISTSUNIST

SUNIST- Sino UNIted Spherical Tokamak

Status of SUNIST spherical tokamak in 2006

HE Yexi, ZHANG Liang, *FENG Chunhua, FU Hongjun, GAO Zhe, TAN Yi, WANG Wenhao, *WANG Long, *YANG Xuanzong, XIE Lifeng

yexihe@mail.tsinghua.edu.cn, 86-10-62791874 (o), 86-10-62782658 (fax)

SUNIST United LaboratoryDepartment of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China

*Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China

This work was supported by National Nature and Science Fund of China (Grant numbers: 10275041 and 10375089) , and International Atomic Energy Agency (Research contract No. 12935/R0) .

The 2nd Research Coordinate Meeting

on Joint Research Using Small Tokamak, IAEAOctober 23 - 26, Beijing

OUTLINE

UNISTUNISTSUNISTSUNIST

SUNIST spherical tokamak

Preliminary resultECR plasma current startupthe 1st step modification for double swing operation of BOH

Further plan

SUNIST spherical tokamak

SUNISTSUNIST

SUNIST main parameters:

major radius R 0.3m

minor radius a 0.23m

Aspect ratio A ~1.3

elongation κ ~1.6

toroidal field （ R0） BT 0.15T

plasma current IP 0.05MA

flux (double swing) ΔΦ 0.06Vs

SUNIST spherical tokamak

SUNIST spherical tokamak magnets and power supply

UNISTUNISTSUNISTSUNIST

coil turn L(H) R(m) ID(kA) VC(V) Capacitor(mF)

TF 24 508 4.72 9.4 200 2560(1280)

HF 236 519 17.8 13 3000 13.3/1280

EF 26 684 15 1.5 1200/120 1(2)/476(18.8)

Vacuum vessel and BV magnet assembling

toroidal magnet pre-assembling

Cross section and designed magnetic surface

SUNIST spherical tokamak

SUNIST spherical tokamak vacuum and vacuum vessel

SUNISTSUNIST

main parameters – vacuum vessel:outer diameter 1.2 m inner diameter 0.13 mheight 1.2 mvolume ~ 1 m3

surface area ~ 2.3 m2

vacuum pumps: TMP (1000l//s)

sputtering Ti pump (200l/s)

cryogenic pump (1500l/s to N2)

wall conditioning: baking: PTC（ Curie point 160 0C)glowing discharge,

siliconization

background pressure: ~ 6×10-5 Pa (between shot

s)

leaking rate on cross seal: ≯=2×10-7 Pam3/s

SUNIST spherical tokamak

SUNISTSUNIST

Typical Discharge in single swing mode

SUNIST spherical tokamak

OUTLINE

UNISTUNISTSUNISTSUNIST

SUNIST spherical tokamak

Preliminary resultECR plasma current startupthe 1st step modification for double swing operation of BOH

Further plan

SUNISTSUNIST

Typical discharge of ECR startup in 2005

Preliminary result

Microwave: Pout < 100kW, t pulse ~ 30 ms, f = 2.45 GHz

background pressure ~ 110-4 Pascalhydrogen pressure ~ 110-2 Pascal during discharge

SUNISTSUNIST

Improving vacuum condition

Preliminary result

top view of the movement of the piezo valveinstalled a cryogenic pump (CRYO-PL

EX 8LP), background pressure down to 5~8x10-5 Pa (between shots)

pulsed gas puffing, moving valve to chamber, shorter puffing duration (~

2ms) and shorter interval between filling and PRF (~3ms)

siliconization, SiH4 + He, DC glow dis

charge

the piezo valve

vacuum vessel

Conduit for pumping

t0~30ms

~8mspuffing pulse

power pulse

t0 ~3ms

~2ms

SUNISTSUNIST Preliminary result

• spiky still• oscillations of H and microwave

reflection causing during lower Bv

• BV effect on ECR startup

2 4 6 8 10

0

1

2W

Time (ms)

2 4 6 8 10

0.0

0.2

0.4

0.6

Ip (k

A)

2 4 6 8 10

01020304050

H (

a.u.

)

2 4 6 8 1006

121824

Bv (G

)

0 2 4 6 8 10 12 14 16 18

0.0

0.2

Vlo

op, V

Time (ms)

0 2 4 6 8 10 12 14 16 18

08

16

Pin

0 2 4 6 8 10 12 14 16 18

08

1624

H,

a.u

.

0 2 4 6 8 10 12 14 16 18-0.8-0.40.00.4

Ip, k

A

0 2 4 6 8 10 12 14 16 18

0153045

Iv, G

current startup with a later BV

current startup with one-up BV

Typical discharge of ECR startup in 2006

SUNISTSUNIST

The effect of BV to H emission and wave reflection

Preliminary result

0 2 4 6 8 10 12 14 16 18

0

10

20

30

0 2 4 6 8 10 12 14 16 18

-20-10

0102030405060

H

(a.u

.)

Time (ms)

Ref

lect

ion

(%)

0 2 4 6 8 10 12 14 16 18

0

10

20

30

0 2 4 6 8 10 12 14 16 18

-20-10

0102030405060

H

(a.u

.)

Time (ms)

Refle

ctio

n (%

)

with Bv (~30G)without Bv

SUNISTSUNIST

Dependence of plasma current on vertical field

Preliminary result

SUNISTSUNIST

Electrode arrangement

Preliminary result

SUNISTSUNIST

Typical discharge with electrode assistance

Preliminary result

SUNISTSUNIST

Plasma current counteracted by electrode current

Preliminary result

SUNISTSUNIST

Performances of preliminary ECR current startup

Preliminary result

The effects of BV on plasma current startup on SUNIST:

- BV applied leading PRF _ plasma current is just spikes.

The dependence of driven IP on vertical field is consistent with

the toroidal plasma current produced by BV drift effect in ECR plasma.

- BV applied during ECR plasma _ plasma current has higher value,

longer duration.

- BV influences on H and reflection of PRF.

The effect of electrode discharge to ECR plasma current

- in co-direction _ IP could increase above 10% (Fig. 7).

- in counter-direction _ IP would be counteracted more obviously

(Fig.8).

OUTLINE

UNISTUNISTSUNISTSUNIST

SUNIST spherical tokamak

Preliminary resultECR plasma current startupthe 1st step modification for double swing operation of BOH

Further plan

modification for double swing operation of BOH

UNISTUNISTSUNISTSUNIST

Modifications of the circuit

shutdown the SCR

increasing ramp-down rate

To

From

t

Iohm,I’

C13.6mF

3000V

SCR DCoil519uH

SCR’C’500uF

3000V

L’ 12uH

R200mOhm

0

Imax

I’

t

s 50

C13.6mF

3000V

SCRD

Coil519uH

modification for double swing operation of BOH

UNISTUNISTSUNISTSUNIST

• With < 10kA Iohm and 200

mohm R, ~20kA Ip is gene

rated and a small flat-top

revealed that could be adj

usted by R and IP.

• Compare to normal ramp-

up ohmic discharge, ≯10k

A Iohm ~30kA Ip

• If loop voltage can be kep

t, the plasma current can

be maintained.4 6 8 10 12 14 16 18

02468

10 4 6 8 10 12 14 16 18

0.00.20.40.60.8 4 6 8 10 12 14 16 18

0

8

16

24 4 6 8 10 12 14 16 18-10-505

1015

Iohm

(kA)

time(ms)

Iv(k

A) Ip

(kA)

Vlo

op(V

)

modification for double swing operation of BOH

UNISTUNISTSUNISTSUNIST

Adding a capacitor bank in order to reverse Iohm , and get longer duration of Ip

C

13.6mF

3000V

SCR

SCR’C’

500uF

3000V

L’ 12uH

R

200mOhm

SCR’’

C’’

1.28F

300V

Iohm

0t

IohmIp

OUTLINE

UNISTUNISTSUNISTSUNIST

SUNIST spherical tokamak

Preliminary resultECR plasma current startupthe 1st step modification for double swing operation of BOH

Further plan

SUNISTSUNIST

Further plan

1 upgrade system

*modification of ohmic field power supply to double swing mode

*upgrade diagnostics: H and SX arrays, visible and UV spectroscopy, W interferometer and reflectometer…

*magnet discharge and plasma configuration controls

2 SUNIST discharge performance

*operation regime, equilibrium and MHD

*edge plasma

*vacuum vessel conditioning effects to discharge3 current startup and RF wave effect on plasma*ECR current startup with or without electrode assistance and BV effects

*possibility transit to typical discharge from non induced start plasma current

*Alfven wave effects on low aspect ratio toroidal plasma.

SUNISTSUNIST

SUNIST- Sino UNIted Spherical Tokamak

Status of SUNIST spherical tokamak in 2006

The 2nd Research Coordinate Meeting

on Joint Research Using Small Tokamak, IAEAOctober 23 - 26, Beijing

THANKS