Experimental study of electron cyclotron heating assisted start-up on J-TEXT

Nuclear Fushion

article

Junli Zhang¹  Peter C de Vries²  Kazunobu Nagasaki³  Donghui Xia¹  Wei Jiang⁴  Zhoujun Yang¹  Zhifeng Cheng¹  Li Gao¹  Xin Xu¹  Zhijiang Wang¹  Nengchao Wang¹  Yonghua Ding¹  Zhipeng Chen¹  Zhongyong Chen¹  Yuan Pan¹  J-TEXT Team¹ 

[1] International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics, State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology;ITER Organization;Institute of Advanced Energy, Kyoto University;School of Physics, Huazhong University of Science and Technology

关键词: experimental study;    ECH;    start-up;    pre-ionization;    J-TEXT;   

DOI  :  10.1088/1741-4326/acd6a7

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

Second harmonic X-mode (X2 mode) electron cyclotron heating (ECH) assisted start-up has been studied experimentally on the J-TEXT device to determine the minimum ECH power requirements to assist breakdown and develop a better physical description of the process. Results indicate that the minimum toroidal electric field for a successful start-up on J-TEXT changed from 2.5;mathrm{V;m^{-1}}to 0.56;mathrm{V;m^{-1}} , and that injecting 300;mathrm{kW}of X2-mode ECH power can ensure robust breakdown. The critical ECH power for successful start-up was determined to be approximately 200;mathrm{kW} . At lower powers ECH was observed to cause ionization, but this did not necessarily result in successful start-up. The effects of varying ECH power, pulse-width and toroidal magnetic field on start-up were also investigated. Higher ECH power leads to quicker, stronger ionization and CIII emission, and is beneficial for burn-through. Higher pre-plasma density caused by high ECH power can decrease the required toroidal electric field for ohmic breakdown, while the enhanced CIII emission may not be good for start-up. The characteristics of the pre-plasma formed by ECH prior to application of the loop voltage were also studied. The toroidal magnetic field affects the initial location where pre-plasma forms and this also affected the subsequent tokamak start-up. The analysis of spatial density showed that the pre-plasma can radially develop at a velocity of 600;mathrm{m;s^{-1}} . Furthermore, it was found that injecting ECH power at the appropriate time with a low power of 150;mathrm{kW}can achieve similar pre-ionization results to the high-power case. The transition from ECH plasma to ohmic plasma suggests that the ECH assisted start-up modified the process of purely ohmic breakdown.

【 授权许可】

Unknown