A large volume microwave plasma source

Abstract

We report on the design, construction, and use of a large cavity microwave plasma source. The source is designed to provide a range of space-plasma-like conditions in the Naval Research Laboratory Space Physics Simulation Chamber. A new feature of the source design incorporates hard anodized aluminum as the internal cavity area surface and does not use the conventional quartz cavity liner which is prone to overheating and cracking with extended use. By placing a number of small plasma outlet holes around the surface of a 36.8 cm output plate, we are able to provide a fairly radially uniform plasma; by further surrounding the production region and exit with an axial pinch magnetic field we are able to extend this region of plasma uniformity further toward the chamber walls and cover a significant portion of the experimental area. The source provides plasmas with selectable densities between 104 and 108 cm−3 and electron temperatures vary from about 0.5 to 2.0 eV.