Radio frequency power system for inductive heating in ion sources

In the past large ion sources have been operated with filaments in conjunction with a high current arc. Tungsten filaments used in this application have a potential disadvantage of undesirable short life times, and they tend to contaminate the source with tungsten deposits. At Lawrence Berkeley Laboratory we have applied radio frequency (RF) induction to a multicusp negative ion source for many years. The RF generator, isolation transformer, matching circuit and RF induction coil are discussed. An equivalent circuit of the induction coil coupled to the plasma in the source is described. The effect of the induction coil geometry on the source plasma coupling is discussed, and measurements of the RF power transfer to the plasma source are given