Microwave-assisted pre-ionization experiments on GLAST-Ⅲ  

作　　者：Riaz KHAN Sehrish SHAKIR Ahmad ALI Muhammad Khawar AYUB Moazzam NAZIR Zia UR-REHMAN Abdul QAYYUM Muhammad Athar NAVEED Sarfraz AHMAD Zahoor AHMAD Rafaqat ALI Shahid HUSSAIN 

机构地区：[1]Pakistan Tokamak Plasma Research Institute,P.O.Nilore,Islamabad 44000,Pakistan [2]Theoretical Physics Division,PINSTECH,P.O.Nilore,Islamabad 44000,Pakistan

出　　处：《Plasma Science and Technology》2021年第8期53-61,共9页等离子体科学和技术（英文版）

基　　金：partially supported by a Grant-in-Aid from the Planning Commission,Government of Pakistan and IAEA Co-ordinated research project(CRP-F13018)under research grant PAK-22840。

摘　　要：GLAss Spherical Tokamak(GLAST-Ⅲ)is a spherical tokamak with an insulating vacuum vessel that has a unique single-passage capability for incident microwaves.In this work,electron cyclotron resonance heating(ECRH)-assisted plasma pre-ionization in GLAST-Ⅲis explored for three radio-frequency(RF)polarizations(the O-,X-,and M-modes)at different toroidal-field(TF)strengths and filled gas pressures.The optimum hydrogen pressure is identified for efficient plasma pre-ionization.A comparison of the plasma pre-ionizations initiated by the O-,X-,and M-modes shows prominent differences in the breakdown time,location,and wave absorption.In the case of O-mode polarization,microwave absorption occurs for a relatively shorter duration,resulting in a bell-shaped electron-temperature(Te)temporal profile.Microwave absorption is dominant in the case of the X-mode,leading to a broader Te temporal profile.The M-mode discharge contains features of both the X-and O-modes.Efficient plasma pre-ionization is achieved in the X-mode polarization for the intermediate TF strengths(with a central toroidal magnetic field B0=0.075 T).Traces of the electron-number density show a similar tendency,as revealed by Te.These results suggest that the X-mode is the best candidate for efficient plasma pre-ionization at low filled gas pressures(10-2 Pa)in small tokamaks.

关 键 词：GLAST-Ⅲ microwave ECRH pre-ionization POLARIZATION 

分 类 号：TL631.24[核科学技术—核技术及应用]