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SUNIST- Sino UNIted Spherical Tokamak

Preliminary experiment of plasma current startup by ECR wave on SUNIST spherical tokamak

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

[email protected], 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

JSPS-CAS Core University Program, 2005

This work was supported by JSPS-CAS Core-University Program on Plasma and Nuclear Fusion, the National Nature and Science Fund of China (Grant numbers: 10275041 and 10375089) , and International Atomic Energy Agency (Research contract No. 12935/R0) .

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SUNIST spherical tokamak

Preliminary result

Remained questions

SUNIST United Laboratory


SUNIST United Laboratory

founded in 2004, consists of Department of Engineering Physics, Tsinghus Unive

rsity (DEP) ; Institute of Physics, Chinese Academy of Science (IOP) and keeping

very close collaboration with Southwestern Institute of Physics (SWIP) and Instit

ute of Plasma Physics, Chinese Academy of Science (IPPAS).

Members of SUNIST LaboratoryHe, Yexi Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-10-6

2791874(lab), 86-10-62782658(fax), [email protected] (e-mail)Yang, Xuanzong Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China 86-1

0-82649132(office), [email protected] (e-mail)Wang, Long Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China 86-10-826

49137(office), [email protected] (e-mail)Feng, Chunhua Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China 86-10-

82649132(office), [email protected] (e-mail)Gao, Zhe Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-10-

62776446(lab), 86-10-62782658(fax), [email protected] (e-mail)Wang, Wenhao Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China,

86-10-62776446(lab), 86-10-62782658(fax), [email protected] (e-mail)Xie, Lifeng Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-1

0-62776446(lab), 86-10-62782658(fax), [email protected] (e-mail)



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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 magnets and power supply


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 vacuum and vacuum vessel

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main parameters – vacuum vessel:outer diameter 1.2 m

inner diameter 0.13 m

height 1.2 m

volume ~ 1 m3

surface area ~ 2.3 m2

vacuum pumps: TMP (1000l//s)

Sputtering Ti pump (200l/s)

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

siliconization

background pressure: ~ 6×10-5 Pa

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


SUNIST spherical tokamak diagnostics and data acquisition

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Diagnosticselectromagnetic probes: 2 Rogowski probes, 9 flux loops (4 inside vessel)

15 2-D minor probes (13 in one poloidal cross section)

electrostatic probes: sets of movable 4 probes for Isi, Φ, and Vtoroidal

Data acquisition: 48 channel ADC: 32ch new, 16ch used in CT-6B


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Typical Discharge


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Preliminary result

Remained questions

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Typical discharge of ECR startup

Preliminary result

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

background pressure < 110-5 Pascalhydrogen pressure ~ 110-2 Pascal during discharge

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Discharge with a group of plasma current peaks

Preliminary result

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Dependence of plasma current on vertical field

Preliminary result

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Electrode arrangement

Preliminary result

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Typical discharge with electrode assistance

Preliminary result

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Plasma current counteracted by electrode current

Preliminary result

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One special discharge with electrode assistance

Preliminary result

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Special discharges in CT-6B in 1997

Preliminary result

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Performances of preliminary ECR current startup

Preliminary result

Plasma current is just a peak ~ hundred millisecond of bottom width.

The dependence of driven plasma current on vertical field

is consistent with the toroidal plasma current by vertical field drift effect in ECR pl

asma.

Plasma current could increase above 10% (Fig. 7) in co-direction

Plasma current would be counteracted more obviously (Fig

.8), in counter-direction

We obtained one special discharge that the current of plasma and elec

trode is cutoff with on density and Iisat limitation, and the s

ame time scale of injected wave

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Preliminary result

Remained questions

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Remained questions

Remained questions

This kind of plasma current peak is impossible to

develop to typical ST plasma current.

We didn't consider the mode conversion to EBW

in microwave launch system, then we faced the density

cut off problem of ECR wave propagated in plasma.

That is an only way to modification the feeding

line & antenna according to the request of mode

conversion to electron Bernstein wave.

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Remained questions

Remained questions

The discharge shown in Fig. 9 suggests that

there is a discharge regime with no limitations of

density cut off on ECR current startup and Ii-sat with

electrode discharge assistance.

The questions are why this regime exists and

how to find it for developing it from occasional event

to reproducible discharge.

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Remained questions

Remained questions

In preliminary experiments, the background

pressure of vacuum vessel increased from less

than 110-5 Pascal up to a balanced value, ~ 310-5

Pascal.

Driven plasma current decreased with the

increase of background pressure just like to scan

fuelling gas to higher pressure.

It is necessary to control wall condition for

further experiments.

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SUNIST- Sino UNIted Spherical Tokamak

Preliminary experiment of plasma current startup by ECR wave on SUNIST spherical tokamak

THANKS

JSPS-CAS Core University Program, 2005

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Vertical field effect on driving toroidal current

Preliminary result

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Toroidal field and ECR layer

Preliminary result

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