Pressure Dependent Characteristics of an Ork Ridge Type Duoplasmatron Ion Source I. Discharge Characteristics

Abstract

The pressure dependence of discharge characteristics of an Ork Ridge type duoplasmatron ion source was studied with a Langmuir probe. It was found that the pressure dependent characteristics relate to the radial component of the magnetic field near the tip of the intermediate electrode. A fire ball of dense plasma is built up at the neck of the intermediate electrode and there a potential difference between the fire ball and anode. It was observed that the potential difference varied from 17 V to 50 V with variation in hydrogen gas pressure. The mean energy of electrons emerging from the anode aperture was measured by an A-C thermocouple. It amounts to 51 eV at a gas pressure of 0.06 Torr. The mean energy of electrons corresponds to the potential difference between the fire ball and anode.