INSIGHT ON CLOSED ELECTRON DRIFT THRUSTERS OBTAINED WITH A DISCHARGE SHUTTER AS DIAGNOSTIC TOOL

A high speed electronic switch of discharge current has been used as a diagnostic tool of closed electron drift thrusters. Analysis of transients in discharge current and plasma spectral emissions leads to an evaluation of electron energy and density losses. Low energy excitation processes populating excited states from ion and neutral metastables are evidenced. Measurements of mean electron axial velocity are compared with neutral collision transport across magnetic field. Finally a strong correlation is evidenced between angular distribution of ejected ions and localization of the ionization zone in the thruster channel.