ABSTRACT
Rf ion sources offer the advantages that they can operate with any type of background gases, in particular, gases such as oxygen that can easily poison tungsten filament cathodes. Rf ion sources are useful when long-life operation or clean plasma production is required. A few hundred watts of rf power are typically required to establish a suitable discharge. Generation of an rf discharge by placing the induction coil inside a multicusp source chamber was tested at Berkeley and Garching for neutral beam applications. For pulse operation, a small hairpin tungsten filament is normally used as a starter for the rf induction discharge. The rf discharge is created between the centrally placed rf cathode and the cylindrical anode. The Rf ion source operates at an excitation frequency of 13.5 MHz and rf power less than 250 W.
