Development of ECE/ECEI diagnostics and MHD-related studies on HL-2A tokamak

Z.C Yang,J Wen,Y Liu,W Chen,M Jiang,Q.W Yang,A.S Liang,X.T Ding,Z.B Shi,N.C Luhmann,W.L Zhong,P.W Shi,Y Xu,E Poli,H Laqua,J Oosterbeek

doi:10.1051/epjconf/201920303014

Z.C Yang, J Wen + Show 14 more

Open Access

https://doi.org/10.1051/epjconf/201920303014

Copy DOI

Abstract

A novel 60-channel electron cyclotron emission (ECE) radiometer has been designed and tested for the measurement of electron temperature profiles on the HL-2A tokamak. This system is based on the intermediate frequency division technique, and has the features of wide working frequency range (60−90 GHz) and high temporal-spatial resolution (3 µs, 1 cm), which covers almost the entire plasma region. Also, an electron cyclotron emission imaging (ECEI) system has been developed for studying two dimensional electron temperature fluctuations. It is comprised of several front-end quasi-optical lenses, a 24 channel heterodyne imaging array with a tunable RF frequency range spanning 60−135 GHz, and a set of back-end ECEI electronics that together generate two 24×8 array images of the 2nd harmonic X-mode electron cyclotron emission from the HL-2A plasma. The measurement region can be flexibly shifted due to two independent local oscillator sources, and the field of view can be adjusted easily by changing the position of the zoom lenses as well. The temporal resolution is about 2.5 µs and the achievable spatial resolution is 1 cm. The ECE/ECEI diagnostics have been demonstrated to be powerful tools to study MHD-related physics including the multi-scale interaction between macro-scale MHD and micro-scale turbulence on the HL-2A tokamak.

Highlights

Electron temperature (Te) is one of the basic parameters in fusion plasma, and its measurements are essential for successful completion of the fusion device mission
It can be diagnosed in various ways, including laser Thomson scattering, soft x-ray using silicon drift detector, Langmuir probes, and electron cyclotron emission (ECE)
A novel 60-channel ECE radiometer has been developed for measuring Te profile and Te variations on the HL-2A tokamak

Summary

Introduction

Electron temperature (Te) is one of the basic parameters in fusion plasma, and its measurements are essential for successful completion of the fusion device mission At present, it can be diagnosed in various ways, including laser Thomson scattering, soft x-ray using silicon drift detector, Langmuir probes, and electron cyclotron emission (ECE). A novel 60 channel ECE radiometer has been developed to measure the Te profile of the entire plasma region with a spatial resolution of 0.5−1 cm. Note that the power divider will introduce large insertion loss and is quite expensive especially at high frequency This direct frequency filtering technique has three advantages: lower cost, wider working frequency range, and higher IF output power. For the routine discharge on the HL-2A tokamak, the measurement range will cover about 66 cm on the midplane, with a spatial resolution of 1.1 cm and temporal resolution of 3 μs

ECEI on HL-2A and the optical optimization

Calibration of the ECE system

Analysis of radial mode structure

Multi-scale interaction between TM and turbulence

Findings

Summary