Microwave Plasma Source for the Negative Hydrogen Ion Production

Abstract

Microwave plasma source for the negative hydrogen ion production was constructed and tested. The plasma source consists of two chambers: a plasma production chamber and a plasma confinement chamber. The production chamber is placed into the strong axial magnetic field and the microwaves (2.45 GHz, up to 5 kW) are introduced through the quartz window along the magnetic field lines. It is found that the suppression of the fast electron loss to the window holder is important to improve the efficiency of hydrogen plasma production. The plasma density increases with the magnetic field strength in the plasma production chamber. For the microwave power of 4 kW the uniform plasma of 3×1012 cm−3 for argon and 3×1011 cm−3 for hydrogen is obtained in the area of 20×20 cm. Electron temperature in the plasma grid region is around 2 eV. The optimum gas pressure is around 6 mTorr.