Breathing modes in HEMP thrusters

HEMP thrusters develop breathing mode oscillations with frequencies in the 100 kHz range during stable operation in test facilities. The mechanism of those oscillations in the HEMP-TDM3a model, developed by Thales Deutschland GmbH, is investigated using a fully kinetic PIC-MCC simulation model. The formation and time evolution of a breathing mode are discussed. The consequences for stable thruster operation are outlined and the oscillation frequency is compared to a 0D predator-prey oscillation frequency estimate. A comparison with an experimental discharge current measurement of a breathing mode is discussed.