Spectroscopic characterization of a novel RF excited plasma cathode electron beam gun design

This work presents a radio frequency (RF) excited electron beam (EB) gun design and experimental results obtained at a frequency of 84 MHz. Details of the design features of the plasma device are given and advantages over thermionic cathode triode EB guns are demonstrated empirically. Advantages include: longer cathode lifetime and reduced maintenance costs; no requirement for a grid electrode, avoiding beam aberration; and rapid beam pulsing. The EB gun has been operated at -60 kV in a vacuum chamber at 10^-5 to 10^-6 mbar and an electron beam of a 3.2 kW power has been extracted. This work gives details on the experimental setup for carrying out emission spectroscopy measurements of the plasma used as electron source and preliminary results on an argon plasma cathode.