|M.Sc Student||Palacio Jorge|
|Subject||Simulation of Plasma Parameters during Hollow Cathode|
|Department||Department of Physics||Supervisors||Professor Yakov Krasik|
|Professor Ehud Behar|
|Full Thesis text|
A 0-D model of the plasma parameters within the orifice of orificed Hollow Cathodes (HC) developed by Mandell and Katz (M&K) is analyzed. The model is explained in detail and its predictions are studied under different hollow cathode operation conditions. The M&K model is solved for the case when the ions have the plasma electron temperature and also when the ions are in thermal equilibrium with the neutral gas at lower temperature than the plasma electrons. A new model based on different assumptions is also developed, and its predictions are analyzed and compared with those of the M&K model. In the new model the plasma ions and neutral atoms are at the same temperature while the plasma electrons have a higher temperature. It is found that the two models predict a similar qualitative behavior for the plasma density, plasma electron temperature and ion output. The two models predict also a similar response of the plasma parameters under rescaling of the electron discharge current, total flow rate and orifice dimensions. The quantitative predictions of the two models can differ by a factor of more than two. In the new model the qualitative behavior of the plasma potential drop along the orifice depends on the radius of the orifice, while in the M&K model such dependence does not exist. In the new model, the plasma ions at the input of the orifice can be dragged into the orifice by the gas flow, while in the M&K model the ions at that location are always driven by the electric field to the insert region.
A 0-D model of the plasma parameters inside the insert region is also studied. The model is solved for two HC with different dimensions in order to illustrate the possible self heating mechanisms of the insert and the possible plasma heating mechanisms. The limitations of the model are carefully analyzed.