Accuracy of using metastable state measurements in laser-induced fluorescence diagnostics of xenon ion velocity in Hall thrusters

Abstract Laser-induced fluorescence measurements of singly-charged xenon ion velocities in Hall thrusters typically target metastable states due to lack available laser technology for exciting the ground state. The measured velocity distribution these ions are assumed reflect state behavior. However, this assumption has not been experimentally verified. To investigate accuracy assumption, a recently developed (Xe II) collisional-radiative model is combined with 1D fluid ions, using plasma parameters from higher fidelity simulations each thruster, calculate and as function position along channel centerline. For HERMeS SPT-100 thruster centerlines, differences up 0.5 km s −1 were observed between velocities. difference less than 150 m within one length exit, but increases thereafter charge exchange (CEX) that reduces mean ions. While both experience same acceleration by electric field, small arise because ionization CEX directly into slower neutral can reduce their different amounts. Therefore, discrepancy may be larger lower propellant utilization efficiency density. example, 1.7 calculated on HET-P70 Note although creation slow influence velocity, most probable should unaffected processes.