Renewal of the interfero-polarimeter diagnostic for WEST

C Gil,G Colledani,M Domenes,D Volpe,A Berne,F Faisse,C Guillon,J Morales,P Moreau,B Santraine

doi:10.1016/j.fusengdes.2019.02.003

C Gil, G Colledani + Show 8 more

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https://doi.org/10.1016/j.fusengdes.2019.02.003

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Abstract

In the frame of the WEST tokamak upgrade project, the Tore Supra combined interferometer-polarimeter diagnostic has been modified to fit the geometry and constraints induced by the implementation of divertor coils in the vacuum vessel. For a good spatial resolution of the plasma, as the vertical ports are now partially obstructed, 8 infrared beams go through a common horizontal port and are retro-reflected on an inner panel and 2 vertical port retro-reflected channels, with specific vacuum mirrors close to the divertor, could be implemented to diagnose the edge plasma.The electronics and the data acquisition have also been renewed to improve the reliability and precision of the measurements. Novel digital electronics with embedded interferometric and polarimetric algorithms produce 1 ms data outputs for real time control.The diagnostic has routinely been operated during the first WEST campaigns. In this article, we detail the new arrangement and discuss the first results with plasma.

Highlights

On fusion plasma tokamak machines, the measurement of the electron and current density can be obtained by interferometry and polarimetry technics, using the information given by Far Infrared (FIR) laser beams crossing the plasma [1]
4) Experimental results The diagnostic has routinely been running during the 2017-2018 WEST restart campaigns and helped to improve the plasma performances up to a 10 s duration and a 3 × 1019 m-2 central line integrated electron density (LID). 4.1 Real time calculations
The post pulse calculated LID and Faraday Angle (FA) are used as inputs in equilibrium codes such as NICE [10]

Summary

Introduction

On fusion plasma tokamak machines, the measurement of the electron and current density can be obtained by interferometry and polarimetry technics, using the information given by Far Infrared (FIR) laser beams crossing the plasma [1]. The line integrated electron density (LID) is calculated for each channel using the phase information Φ of two probing beams that have different wavelengths λ (195 and 119 microns). They are superposed to cross the plasma and they are separated toward the detectors [ref 3 p. This double phase information enables to calculate the LID by eliminating the path length component in equation (1)

Methods

Results

Conclusion