Advanced probes for edge plasma diagnostics on the

CASTOR tokamak 探针在托卡马克边界等离子体诊断中的应用

组员 : 顾翔 陶军 金钊 吴铭钐　胡文慧 等离子体所 报告人 胡文慧2014.10.15

J Stöckel,et al, Advanced probes for edge plasma diagnostics on the CASTOR tokamak, Journal of Physics, Conference Series, 63 (2007), 012001

Fig.1 CASTOR -Czech Academy of Sciences TORus

Major radius 0.4 m

Minor radius 0.1 m

Toroidal magnetic field( 环向磁场 ) <1.3 T

Plasma current <15 kA

Pulse length 50 ms

Plasma temperature 0.20 keV

Plasma density ~ 1×1019 m-3

Confinement time < 1 ms

Edge density ~2×1018 m-3

Edge temperature 10-40 eV

Built in Kurchatov Inst. Moscow 1958Operational in IPP Prague since 1977Reconstructed (new vessel) 1985Associated to EURATOM 1999Last shot 26 Oct 2007

CASTOR 　 tokamak

It is evident that understanding of underlying physics in the edge plasma requires simultaneous measurement:

- Plasma parameters like density, temperature, potential with a good spatial and temporal resolution (turbulence) ( 等离子体温度 , 密度 , 电势测量需要高的空间和时间分辨率 )

- Plasma flows in poloidal (and toroidal) direction ( 等离子体在换向和极向两个方向上都有流通量 )

A practical solution for small scale experiments => electric (Langmuir) probes ( 朗缪探针 )

Alternatively in large experiments (more sophisticated diagnostics):• Fast cameras are used to visualize the density fluctuations ( ~100 k USD)( 足够快的可视化测

量等离子体密度波动变化 )

• Beam emission spectroscopy• Microwave scattering• ……

What diagnostics are required ?

{1 exp[ ( ) / ( )}satprobe ion float probe eI I e V V kT

Single Langmuir probe

简单的工作原理示意图

Floating potentialIon saturation current

Rake probe on CASTOR-----Langmuir Probe Array ( 朗缪探针阵列 )

•时间分辨率 1~2 ms•16 small tips (diameter=2 mm) • Distance of tips 2.5 mm• Total extension 35 mm

Fig.2 Picutre of single (left) and the double (right) rake probes

The individual tips can operate in a sweeping mode and the current – voltage characteristic can be measured to determine the radial profile of electron density and temperature

Fig.3 Radial profile of the electron temperature at the edge of CASTOR

Fig. 4 Electric circuit for measurement of the floating potential and the ion saturation current for probe arrays used on CASTOR. The switch is used to change the mode of operation between shots of operation.

Fig. 5 Radial profile of the floating potential Vfl

(red circles) and the ion saturation current density Jsat (blue triangles).

红：离子饱和流测量环路蓝：悬浮电位测量环路

2D Array of Langmuir Probes （二维探针矩阵）

2D matrix of 64 tips

空间分辨率Poloidal resolution 6 mmRadial resolution 4.5 mm

limiter

separatrix

A snapshot of potential structures

poloidally: 42 mm

radi

al p

osit

ion

[mm

]

2D matrix of 64 Langmuir probes

2D Structure of Edge Turbulence on the CASTOR Tokamak

Poloidal ring of electric and magnetic probes ( 极向探针环 )

Fig. 6 Picture of the full poloidal ring of 96 Langmuir probes. Probes are located at the radius r = 85 mm and their mutualpoloidal distance is 5.5 mm

Fig. 7 Poloidal structure of edge turbulence 例如悬浮电位 , 等离子体密度

Segmented tunnel probe (STP) ( 隧道探针 )

Fig . 8 Schematic drawing of the tunnel probe

Fig . 9 the temporal evolution of the electron density and temperature实现瞬态测量，在数据采集频率的限制下，时

间分辨率为 1μs

B

Fig. 10 Schematic drawing of the probe head of the STP. Two segmented tunnels are mounted back-to-back

Mach probe ( 马赫探针 )

black platesegments

Fig. 11 隧道探针和阵列探针测量的电子温度比较

为了为消除等离子体流动 (plasma flows) 带来的误差

downs

upsII /II2.3lnM

s

II

c

v

Ball pen probe --- 直接测量等离子体电位

ln

/

efl

e isat sat

kTV R

e

R I I

等离子体电位把探头伸进或审处探针壳壳，改变 R 值，当探头位于 h=0 时， R=1 ， flV

优点是能够承受高的等离子体能量负荷，可以用在大型 tokamak 里面得到足够高的时间和空间分辨率的测量结果

Gunderstrup probe--- 测量等离子体粒子通量

Top View

Polar diagram of Ion saturation current

离子饱和流的极向分布图

Several (eight) segments with a different orientation with respect to magnetic field lines

The Gundestrup cauldron

Parallel & perpendicular Mach numbes M||

and M⊥ derived with a high temporal resolutionfrom the shape of the polar diagram探针之间的间隙和角度偏差导致只有垂直和平行马赫数较为准确

Bt, Ip

环向和径向不对称说明既有环向通量又有径向通量

Tools for edge plasma diagnostic and fluctuation measurements on CASTOR (Summary)

• Classical Langmuir probes – IV characteristics, local Te , ne , Vfl at the plasma edge, routine measurements

• Radial & Poloidal arrays of Langmuir probes for spatially-temporally resolved measurements of plasma fluctuations

• Advanced probes – Segmented tunnel probe - a quite novel concept for fast Te and Ti measurements

•Ball pen probe & Emissive probe – Direct measurement of plasma potential

• Oriented probes - Gundestrup and Mach probe for flow measurements during biasing experiments