Langmuir probe analysis of a BF3 discharge in a high current ion source

Optimisation and performance of an ion source demands an intimate knowledge of the role of gas and surface phase processes in the cracking of the precursor molecule. To this end, it is necessary to understand the characteristics of the source plasma and the role of physical configurations of the arc chamber and arc control parameters. In BF3 plasmas, there is clear evidence that high energy electrons play a significant role in the production of B+ ions. Therefore, the plasma conditions which optimise the production of the species of interest (BF2+ and B+) have been studied using a symmetrical, floating double Langmuir probe arrangement that inherently lends itself to the study of the characteristics of the high energy electrons, with minimal perturbation of the plasma. In this paper, the electron temperature dependence on the source control parameters are the main areas investigated. The electron temperatures measured for two different source configurations are also compared. The dependence of electron temperature on different operating conditions is found to be different. The electron temperature is found not to be uniform across the arc chamber.