A Low-Pressure Gas-Discharge Ion Source with a Hollow Cathode and an Output-Aperture Diameter of 420 mm

摘要

A gas-discharge ion source with a hollow cathode 700 mm in diameter and 500 mm in length is described. Two small-area anodes are positioned at the ends of the hollow cathode opposite to each other. A 420-mm-diameter extracting electrode is placed along the lateral wall of the hollow cathode at a distance of 250 mm from its center symmetrically relative to the anodes. A hot cathode is placed opposite to the extracting electrode. A beam of oxygen ions with a current density of up to 0.2 mA/cm{sup}2 and a nonuniformity <12% over a 420-mm-diameter area at a distance of 200 mm from the extracting electrode was obtained. The optimal operating parameters of the ion source working with oxygen are as follows: a discharge current of 0.8-1.2 A, an operating pressure of (0.6-0.8) × 10{sup}(-4) Torr, and an extracting voltage of up to 400 V.