Ion energy distribution measurements of a radiofrequency plasma source immersed in Vacuum

Summary form only given. Measurements of the ion energy distribution downstream of a rf plasma source are performed using a Retarding Potential Analyzer (RPA). The plasma source is an assembly of six solenoid magnets, an antenna, and a quartz tube that are all surrounded by a steel case to increase the magnetic field strength and uniformity. This source is installed and operated inside the Junior Test Facility (JTF) at the Plasmadynamics and Electric Propulsion Laboratory (PEPL), which is connected to the Large Vacuum Test Facility (LVTF) through a 60cm diameter gate valve. Thus, JTF can utilize LVTF´s seven nude cryopumps to hold the background pressure below 5×10^-6 Torr during operation. RPA characteristics are collected at a number of operating conditions when the gate valve is both open and closed to investigate the effect of background pressure on ion energy measurements. Electrical characteristics of the discharge are also investigated.