Determination of species yield of ion sources used for intense neutral beam injection

For efficient plasma heating, ion sources of neutral beam injectors should be capable of producing ion beams with an atomic fraction of 90% or higher. Diagnostic techniques for quantitatively determining source species yield have been developed and evaluated. These include a magnetic momentum analysis of the unneutralized ions passing through the neutralizer, an energy analysis of the atomic beam by electrostatic separation of ions emanating from a stripping cell, and a quantity versus implantation depth analysis of hydrogen implanted in a crystal by the Secondary Ion Mass Spectrometer (SIMS) technique. The operational features and the advantages and disadvantages of each technique will be discussed. If the effects of beamlet optics, energy straggling in the accelerator, and neutralizer gas scattering are taken into account, the results of the measurements using the three techniques are shown to be mutually consistent within experimental error