A miniaturized 2.45 GHz ECR ion source at Peking University
Wen Jia-Mei, Peng Shi-Xiang, Ren Hai-Tao, Zhang Tao, Zhang Jing-Feng, Wu Wen-Bin, Sun Jiang, Guo Zhi-Yu, Chen Jia-Er
       

(color online) The fraction of H+, , as a function of gas pressure.