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

Internal electrostatic and magnetic measurement in SUNIST

S. Chai，W. H. Wang

* E-mail: chaisong@sunist.org

The Second A3 Foresight Workshop on Spherical Torus, Jan. 6-8, 2014, Tsinghua University, Beijing, China

Layout of the Windows

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

R (m)

Z (m

)

The magnetic probesMoveable multi-probes

Moveable inner Langmuir& magnetic probe

Langmuir probes

Poloidal magneticprobes array

Toroidal magnetic probesarray & flux loops

Top view of SUNIST

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

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

Tips configuration

Typical results

Picture of the probe

• An integrated probe-- A magnetic probe-- A 4 tips Langmuir probe set

• Purpose-- To get local plasma pressure and magnetic pressure simultaneously

• Future plan-- Smaller size, more “local”

Moveable Langmuir-magnetic Probe(2)

Raw signals from the Langmuir-

magnetic probe

The moveable Langmuir-magnetic

probe

-40-20

0

I P (k

A)

Shot 130108002

-505

VF2

(V)

0102030

VF1

(V)

0

100

V+ (V

)

02040

I SI (m

A)

30 35 40 45 50 55 60 65 70-5

0

5 x 10-4

Time (ms)B

P (a

.u.)

2013

Moveable Multi-probes (3)

Langmuir Probe

Magnetic Probe

Retarding-field Energy Analyzer （ RFEA ）

Drawing of moveable multi-probes

Parameters of 4 tips Langmuir probe:L=3mm,d=1mm ,Ap=10.21mm2

Parameters of magnetic probe:N=310, d=10mm S=78.5mm2 NS=0.0243m2

Entrance slit: 5mm*0.4mmMesh Aperture: 0.2mm

38*20*20mm

Retarding-field Energy Analyzer

Principle of the RFEA(1)

(1):Ion velocity distributions at the tokamak edge; R.A.Pitts; 31 May 1991 (2):W.H.Wang;

The relationship between collected Isi and scan potential:

)(21)(

).()(exp21)(

psTiii

pipsTii

VcATenIVI

VkTVZecATenVI

Volt-ampere relationship(2)

-250V 300V 27V

Test Result

a

b

Vf1

Vf2

Isi

A Experimental result of magnetic probe; b Experimental resultof Langmuir probe;

Location of probe Bp10

*100 mA

*20 V

*20 V

9

Further work

RFEA: radial profile of TiMagnetic Probe: radial profile of BpLangmuir probe: radial profile of Ne,Te

Bootstrap current density:

Moveable multi-probes Bootstrap current

John Wesson, 《 TOKAMAK 》 , chapter 4.9

10

SummaryInternal electrostatic and magnetic measurement in SUNIST includes ：1. A set of Langmuir probe: On one side of the vacuum

chamber2. Toroidal and poloidal magnetic array & flux loops: EFIT,

displacement, feedback control…3. A set of moveable magnetic & Langmuir probes: On the

other side of the vacuum chamber4. A set of moveable multi-probes: Profile of Te, Ti, Ne,

bootstrap current…

Thank you for your attention!

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

技术难点

Entrance slit: 5mm*0.4mmMesh Aperture: 0.2mm

聚四氟乙烯 Teflon

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

13

磁探针测得的磁场变化情况

0 10 20 30 40 5012

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20

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23

Te [e

V]

Distance [mm]

Triple Probe Te, Ne

-0.03

-0.028

-0.026

-0.024

-0.022

-0.02

-0.018

-0.016

-0.014

-0.012

-0.01

-0.008

-0.006

-0.004

-0.002

Ne [1

018

m-3

]

TeNe

0 10 20 30 40 50160

165

170

175

180

185

190

Distance [mm]

Bp

[Gs]

Triple Probe (Bp)

磁探针测得的磁场变化图像T=47~52ms 测得的 Ne 、 Te 和 Bp 的值

Parameters of SUNIST R0 0.3 m

a 0.23 m

BT 0.15 T

ΨOhm 60 (37) mV.s

IP 50 (70) kA

Pulse length 15 (20) ms

ne ~1×1019 m-3

Te ~100 eVRed: achieved

Diagnostics and heatinga. Quadruple probe ×1

b. B-dot probes ×15, flux loops ×13c. Internal composite probe×1

d. Interfermetor(94 GHz)×1e. Reflectometer(26~40 GHz)×1

f. Radiometer(2~12 GHz)×1g. Spectrometer(380~600 nm)×2

h. Fast camera(5130 fps)×1i. Hard X-ray, NaI×1,CdZnTe×2

j. ECH(5 GHz/200 kW ， under test)×1

k. AWH(0.4~1 MHz/400 kW)×1

j

kk

k k

a

cd, g, i

e, f, h

Progress of AW experiments

TMPCryogenic Pump,

Ion Sputtering Pump

Fast Visible Camera

Photodiodes, NaI Detector

Piezo-valves

Toroidal Field Coils

94 GHz Interferometer

Antenna 4

Antenna 3Antenna 2

Antenna 1

Antenna Strap

FeedthroughBN Limiters

Plasma Torus

CdZnTe Detector

2.45 GHz Pre-ionizer

Topview of SUNIST Antennas and the plasma torus