Desing and performance of a hot cathode magnetically collimated arc dischrge ion source

Abstract

A hot cathode arc discharge type ion source is described. The discharge is collimated in an axial magnetic field and the ion beam is extracted axially. The maximum total ion current of the source, tested with hydrogen, is 42 ma. The extraction system allows focusing of almost 100% of this current. The limiting factor of the maximum ion current is analyzed. Although strong arc discharges could allow the extraction of higher ion currents, space charge spreading causes the ion beam to hit the front surface of the extracting electrode. Secondary electrons, released there, are focused back into the arc chamber producing instabilities of the source. A convenient means of regulation or modulation of the beam current is described. A magnetic analysis of the extracted beam shows about 34% atomic ion current.