Spectral characterization of LaB₆Hollow Cathode operation on Kr gas

Krypton gas is a viable alternative to Xenon propellant [1] for Electric Propulsion. Hall Effect Thrusters are being used commercially with Kr due to its significantly lower cost, but such operation was not studied as intensively as for Xe. We have previously reported initial results for Busek’s BHT-200 200W thruster running on Kr propellant [2]. In the present work we are investigating the Kr operation of the corresponding hollow cathode using a LaB₆ emitter. Broad EUV-VIS spectra of the hollow cathode are presented first by looking straight into the cathode orifice with vacuum spectrometer. Next, detailed NIR-VIS spectra are discussed. Particular attention is given to LaB₆ erosion product emission lines and their dependance on propellant flow rate and discharge current. The high-resolution spectroscopic system [3] is used to decipher discharge composition with sub-pm resolution inside the cathode and in the emitted plasma plume.