Characterisation of an RF excited argon plasma cathode electron beam gun

Abstract

This work describes the experimental set up used for carrying out spectroscopic measurements in a plasma cathode electron beam (EB) gun. Advantages of plasma cathode guns over thermionic guns are described. The factors affecting electron beam power such as plasma pressure, excitation power and plasma chamber geometry are discussed. The maximum beam current extracted was 53 mA from a 0.5 mm diameter aperture in the plasma chamber. In this work, the electron source is an argon plasma excited at 84 MHz. The pressure in the plasma chamber was measured to be within 0.9 to 1.2 mbar and was controlled by varying gas flow rates. The vacuum chamber was at a pressure of 10^-5 mbar.