Southwestern Institute of Physics, Sichuan, Changdu 610041, China;
Southwestern Institute of Physics, Sichuan, Changdu 610041, China;
Southwestern Institute of Physics, Sichuan, Changdu 610041, China;
Southwestern Institute of Physics, Sichuan, Changdu 610041, China;
Southwestern Institute of Physics, Sichuan, Changdu 610041, China;
Southwestern Institute of Physics, Sichuan, Changdu 610041, China;
Southwestern Institute of Physics, Sichuan, Changdu 610041, China;
plasma; wall conditioning; impurity;