Effect of positive and negative ion energies on H− destruction by mutual neutralization in low-pressure plasmas

Abstract

The effect of plasma potential profile and collisions with neutrals and charged particles upon positive and negative ion energies has been studied in a low-pressure (2–13.6 mTorr) hybrid magnetic multicusp hydrogen discharge. When the plasma density is lower than 1011 cm−3, the negative ion temperature is always close to the gas temperature, while the positive ion temperature goes down from 1 to 0.1 eV when the pressure goes up. The observed reduction of the relative negative ion density when the pressure is increased is shown to be related to the reduction of positive ion velocities and to the associated increase in the mutual neutralization rate coefficient.