Comparative Analysis of High-Frequency Plasma Drivers with Various Protective Screens for Atomic Injectors with Multi-Second Pulse Duration

Atomic beam injection is one of the main methods of plasma heating in thermonuclear facilities. An injector of high-energy hydrogen atoms for plasma heating based on the acceleration and neutralization of negative hydrogen ions is being developed at the Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences. The injector uses a surface plasma source, in which a plasma flow is created using a radio-frequency driver: an induction radio-frequency (RF) discharge, ignited inside a cylindrical ceramic chamber when an RF voltage is applied to an external antenna. As a part of this work, a new version of the RF driver is being developed. A protective screen is used to prevent overheating and erosion of the ceramic wall of the driver. The operation of RF driver with different protective screens is studied. These screens reduce the efficiency of RF power transmission into the discharge, but make it possible the operation of the ion source in multi-second or steady-state pulses.