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The Second A3 Foresight Workshop on Spherical Torus , Jan . 6-8, 2014, Tsinghua University, Beijing, China. Internal electrostatic and magnetic measurement in SUNIST. S. Chai , W. H. Wang. Department of Engineering Physics, Tsinghua University, Beijing, P. R. China .

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internal electrostatic and magnetic measurement in sunist
The SecondA3 Foresight Workshop on Spherical Torus,

Jan. 6-8, 2014, Tsinghua University, Beijing, China

Internal electrostatic and magnetic measurement in SUNIST

S. Chai,W. H. Wang

Department of Engineering Physics, Tsinghua University, Beijing, P. R. China

* E-mail: chaisong@sunist.org

layout of the windows
Layout of the Windows

Top view of SUNIST

Langmuir probes

Toroidal magnetic probes

array & flux loops

Poloidal magnetic

probes array

Moveable inner Langmuir

& magnetic probe

Moveable multi-probes

The magnetic probes

langmuir probes 1
Langmuir Probes(1)
  • Probe design

--Total movable distance

      • ~13 cm ( 0.78a ~

1.35a)

--Tips configuration

      • 4 tips: 2 float, 2

connected for Isi

      • Material: Mo
  • Typical results

-- ne, Te, fp, and ff

-- Shot by shot scanning

Tips configuration

Picture of the probe

Wang W. H., et al., PPCF 2005

Typical results

moveable langmuir magnetic probe 2
Moveable Langmuir-magnetic Probe(2)
  • An integrated probe

-- A magnetic probe

-- A 4 tips Langmuir probe set

  • Purpose

-- To get localplasma pressure and magnetic pressure simultaneously

  • Future plan

-- Smaller size, more “local”

2013

Raw signals from the Langmuir-magnetic probe

The moveable Langmuir-magnetic probe

moveable multi probes 3
Moveable Multi-probes (3)

38*20*20mm

Parameters of 4 tips Langmuir probe:

L=3mm,d=1mm ,Ap=10.21mm2

Langmuir Probe

Parameters of magnetic probe:

N=310, d=10mmS=78.5mm2 NS=0.0243m2

Magnetic Probe

Entrance slit: 5mm*0.4mm

Mesh Aperture: 0.2mm

Retarding-field Energy Analyzer(RFEA)

Drawing of moveable multi-probes

retarding field energy analyzer
Retarding-field Energy Analyzer

Volt-ampererelationship(2)

Principle of the RFEA(1)

The relationship between collected Isi and

scan potential:

-250V

300V

27V

(1):Ion velocity distributions at the tokamak edge; R.A.Pitts; 31 May 1991

(2):W.H.Wang;

test result
Test Result

a

*20V

b

Vf1

*20V

Vf2

Location of probe Bp10

A Experimental result

of magnetic probe;

b Experimental result

of Langmuir probe;

*100mA

Isi

further work
Furtherwork

RFEA: radial profile of Ti

Magnetic Probe: radial profile of Bp

Langmuir probe: radial profile of Ne,Te

Bootstrap currentdensity:

John Wesson,《TOKAMAK》, chapter 4.9

Moveable multi-probes

Bootstrap current

summary
Summary

Internal electrostatic and magnetic measurement in SUNISTincludes:

A set of Langmuir probe: On one side of the vacuum chamber

Toroidal and poloidal magnetic array & flux loops: EFIT, displacement, feedback control…

A set of moveable magnetic & Langmuir probes: On the other sideofthe vacuum chamber

A set of moveable multi-probes: Profile of Te, Ti, Ne, bootstrap current…

slide12

技术难点

狭缝的尺寸:足够小,不大于2倍的鞘层厚度,6-8倍的德拜长度

SUNIST上的一些参数:Te=20eV,Ne=3*1018m-3

钨钼合金(绝缘、抗热震、高热材料,但难开缝,需用等体切割)

厚度0.5mm,切口长*宽 (3~5mm*0.1mm)

栅网孔径:要求离子通过时整个栅网等电位,

ni’为分析器内部离子密度,由于分析器内密度远小于外部,所以这个条 件比较容易满足。材料为钼丝,网孔径200um

收集板:纯铜

电源:低频功率源 频率高于50kHz,功率在几十kw量级,扫描电压正负250V

HA-405A 高压放大器 最高频率500kHz,扫描电压0~400V

Entrance slit: 5mm*0.4mm

Mesh Aperture: 0.2mm

聚四氟乙烯 Teflon

Here, plasma potential outside the RFEA; niion density; Cs the ion-acoustic velocity; A is the slit window area; TT is the total transmission coefficient. So

slide14
磁探针测得的磁场变化情况

磁探针测得的磁场变化图像

T=47~52ms测得的Ne、Te和Bp的值

slide15

j

a

k

k

e, f, h

k

k

c

d, g, i

progress of aw experiments
Progress of AW experiments

Toroidal Field Coils

Antenna 4

Plasma Torus

Antenna 1

  • Cryogenic Pump, Ion Sputtering Pump

TMP

Photodiodes, NaI Detector

Fast Visible Camera

2.45 GHz Pre-ionizer

Antenna 2

Antenna Strap

Feedthrough

BN Limiters

Antenna 3

Piezo-valves

CdZnTe Detector

94 GHz Interferometer

Topview of SUNIST

Antennas and the plasma torus