In this work, we considered a microwave generated plasma, in a toroidal device. In this set up, we tend to meet the conditions for several known plasma instabilities. Not all the gas in the chamber was ionized. Using a Langmuir probe we were able to determine the population temperature and the plasma density in the chamber. The existence of a plasma was determined by measuring the strength of reflected microwaves. We varied the fill pressure in the chamber, as well as the strength of an externally imposed magnetic field. From this, we determined that the plasma temperature decreased with an increased fill pressure. Plasma density however, appears largely unaffected by the fill pressure. Imposing any external magnetic field causes the temperature to drop, though beyond this, the field strength does not appear to influence the temperature. For certain magnetic field strengths tested, the plasma density increased. Further work needs to be done on how temperature and density vary with distance from the chamber wall.
Rawlins, Wesley, "Langmuir Probes in a Microwave Generated Plasma" (2015). Physics Capstone Project. Paper 21.