Theoretical and experimental study of the overdense plasma generation in a miniaturized microwave ion source

• Published in: Journal of applied physics 2022-08, Vol.132 (8)
• Main Authors: Wu, Wenbin, Peng, Shixiang, Zhang, Ailin, Ma, Tenghao, Jiang, Yaoxiang, Li, Kai, Cui, Bujian, Guo, Zhiyu, Chen, Jiaer
• Format: Article
• Language: English
• Subjects: Applied physics; Continuous radiation; Cyclotron resonance; Discharge; Electric fields; Electron cyclotron heating; Electron cyclotron resonance; Electron density; Electron energy; Evolution; Ion sources; Power efficiency; Surface waves
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/5.0098645

To understand the plasma evolution mechanism of microwave ion source (MIS), a hybrid discharge heating (HDH) mode is proposed. That mode contains two parts: ignition discharge by surface wave plasma (SWP) and ionization by electron cyclotron resonance. Compared with the traditional electron cyclotron heating (ECH) mode, the HDH mode has a wider scope of application for MIS with a chamber diameter smaller than the cutoff size. The spatio-temporal evolution of electric field, power deposition, electron temperature, and electron density of a miniaturized microwave ion source (MMIS) at Peking University is investigated based on the HDH mode. In addition, the MMIS is optimized based on the theoretical results of the HDH mechanism. Preliminary experiments show that a mixed hydrogen continuous wave beam of up to 25 mA at 30 keV can be extracted with a power efficiency of 25 mA/100 W.