Using a helicon source to simulate atmospheric re-entry plasma densities and temperatures in a laboratory setting

Abstract

The purpose of this research is to develop a plasma system capable of reproducing plasma densities found during atmospheric re-entry of a capsule. We developed a 150 mm diameter helicon source at the University of Michigan Plasmadynamics and Electric Propulsion Laboratory (PEPL) and used a Langmuir probe to characterize plasma properties downstream. The helicon source was operated with argon gas at a background pressure of 0.6 mTorr. We used a commercial RF-compensated single Langmuir probe to measure ion number density and electron temperature in the region downstream of the helicon source where we want to create conditions similar to those found during hypersonic flight within the atmosphere. We measured these values with and without the presence of a large 450 mm wide by 550 mm long surface downstream in the horizontal plane to simulate a vehicle surrounded by plasma in order to determine how the downstream body affects plasma properties. We found that the presence of a surface downstream of the helicon source lowers the downstream plasma density range from between 1.7 10 17 and 3.3 10 17 m 3 down to 0.55 10 17 and 1.3 10 17 m 3 . In addition, the peak plasma potential decreases from 65 to 55 V, but the electron temperature remains unchanged ranging between 1.5 and 6.5 eV.