Adanced Interferometry Techniques for Burning Plasmas

组员 : 顾翔 陶军 金钊 吴铭钐　胡文慧 彭浩 等离子体所

Brower D L, Ding W X, Mirnov V V, et al. Advanced Interferometry Techniques for Burning Plasmas[C]//AIP Conference Proceedings. 2008, 988(1): 92.

报告人：顾翔

For future burning plasma experiments, all diagnostics must be re-evaluated in terms of their measurement capabilities and robustness to the new environment

This paper will explore a variety of phase measurement techniques for the main body and divertor regions that can be utilized on burning plasma experiments like ITER and beyond.

The scope of this work

We will focus on a variety of phase measurement techniques：

Conventionnal interferometryFaraday rotationCotton-Mouton effectFizeau interferometry

Conventionnal interferometry

基本原理示意图：

Conventionnal interferometry

The resulting phase measurement can then be related to the plasma density according to the relation:

Three assumptions:1.Magnetic field can be ignored2.The plasma is stationary3.Temperature effects are unimportant

𝜙

Conventionnal interferometry

If path length changes do occur, an extra phase term will be included. And if this term is large ,additional information is required to resolve the plasma density. An extra phase term:

One way is adding an additional probe beam with spatial offset

This approach is commonly referred to as 2-color interferometry (双色干涉仪 ).

Conventionnal interferometry

2 equations2 unknowns

We will get these:

If the two laser wavelengths are far apart, these can be written as:

Conventionnal interferometry

Drawback: fringe skip errors （条纹跳跃误差）

Dispersion interferometer

Differential interferometer

Two ways

Conventionnal interferometry

相位差：

V. P. Drachev, Yu. I. Krasnikovand P. A. Bagryansky Dispersion interferometer for controlled fusion devices Rev. Sci. Instrum. 64, 1010 (1993)

Conventionnal interferometry

Differential interferometer（微分干涉仪） :Conventional interferometer phase shift induced by plasma, in a cylindrical geometry :

After Abel inversion(阿贝尔反演 ):

Ding W X, Brower D L, Deng B H, et al. Electron density measurement by differential interferometry[J]. Review of scientific instruments, 2006, 77(10): 10F105.

Conventionnal interferometry

Differential interferometer（微分干涉仪） :

Faraday Rotation

http://en.wikipedia.org/wiki/Faraday_effect

In physics, the Faraday effect or Faraday rotation is a magneto-optical phenomenon, that is, an interaction between light and a magnetic field in a medium.

Faraday Rotation

This measurement is immune to fringe counting errors

The results can be expressed as the phase difference between R-wave and L-wave

Faraday Rotation

Faraday Rotation

Cotton-Mouton Effect (科顿 -穆顿效应 )

In physical optics, the Cotton–Mouton effect refers to birefringence in a liquid in the presence of a constant transverse magnetic field

http://en.wikipedia.org/wiki/Cotton%E2%80%93Mouton_effecthttp://baike.baidu.com/view/675966.htm?fr=aladdin

Cotton-Mouton Effect

The results can be expressed as the phase difference in the O-wave and X-wave

Cotton-Mouton Effect

Fizeau Interferometer (菲佐干涉仪 )

Fizeau effect: the fizeau effect is the relativistic phase shift of an electromagnetic wave associated with movement of a dielectric medium.

In the moving electron fluid, the phase shift experienced by an electromagnetic wave including Fizeau effect is

Fizeau Interferometer

Multiplying the Fizeau phase shift by the electron charge provides a line-integrated measure of the toroidal electron current density.

Finite Temperature Effects (有限温度效应 )

Finite temperature effects

Relativistic effects

the electron plasma frequency

The measured phase

increase

decrease

Mirnov :The conbined effect for ITER

All interferometer and polarimeter phase shifts discussed to this point are based on cold plasma dispersion relation(i.e )

Finite Temperature Effects

Phase correction factors

Measured phase shifts:

Finite Temperature Effects

Fluctuation Measurements (波动测量 )

It is possible to make measurement with both high phase resolution and high time response