An experimental investigation of the proton fraction in a three electrode 2.45 GHz ECR ion source

Abstract

The ion beam extracted from a proton ion source contains H+ ion along with H2 + and H3 + molecular ions. In this work, the ionic fractions in the extracted beam of ECR ion source were measured using an analyzing magnet. A computerized proton fraction measurement setup is described in detail with instrumentation and control for pulsed operation of the ECR ion source. A timing diagram has been incorporated for trigger synchronization illustrating the process of pulsing the plasma, controlling the analyzing magnet parameters and acquiring data about the magnetic field and beam current. The proton fraction was measured in two cases, in the first case using SS304 plasma chamber and in the second case incorporating aluminium (Al) cylinder and boron nitride (BN) plates inside the plasma chamber. In the first case, the proton fraction was found to be in the range of ∼60% and in the second case because of the presence of secondary electron donors it increased to 93%. In order to understand the enhancement of H+ fraction in the hydrogen plasma, plasma parameters (ne , Te and EEDF) and its dependence on microwave power and neutral gas pressure were investigated.