Development of a hybrid PIG-ECR ion source

Abstract

A combined ion source with 20 cm beam diameter, utilizing both a cold-cathode Philips or Penning ionization gauge (PIG) discharge and an electron cyclotron resonance (ECR) discharge, has been built and tested. The ion source has been designed to study what effects, if any, might be induced by superimposing microwave power at the ECR condition onto a cold-cathode PIG ion source at low pressures (≤10 −4 Torr). The first experiments with argon gas indicate that the ECR coupling at low pressures results in: (a) transformation of the PIG discharge mode with a dominant anode fall into the hybrid discharge mode with a dominant cathode fall; (b) stabilization of the PIG discharge; and (c) enhanced ion beam output due to increased ionization inside the ion source. The ion beam current is 150 mA (with a beam current density at its axis of 0.35 mA/cm 2), at an anode voltage of 750 V, a microwave power of 200 W and a gas pressure of 0.05 mTorr. The ion source design and the results of preliminary experiments are presented. A stable low-pressure operation mode of the ion source might be promising for broad ion beam production.