Improvement of extracted ion beam from cold cathode Penning ion source

Abstract

A direct current cold cathode Penning ion source is operated at the optimum parameters and pressure equal to 7×10−4 mmHg using argon gas. It consists of a copper cylindrical hollow anode and two movable molybdenum discs cathodes are placed symmetrically at two ends of the anode. Argon ion beam is extracted from the ion source by using extractor of different aperture diameter equal to 2.5, 3, 3.5, 4 and 4.5mm respectively. The extractor is placed at different distances from the ion exit aperture equal to 5, 10, 15 and 20mm respectively. It is found that at extractor aperture diameter equal to 3.5mm, ion exit aperture - extractor distance equal to 10mm and extraction potential applied on the extractor is equal to −500V, the optimum extracted ion beam current equal to 543 μA can be obtained. A comparison for Penning ion source without and with the extractor is made at the same optimum operating parameters, it is found that the extracted ion beam current from Penning ion source with the extractor increases about twice its initial value of Penning ion source without the extractor.