Development of a 25 keV Ion Beam Source for Fast-Ion Studies on the Large Plasma Device*

A helium ion beam source (25 kV, 3 A) has been constructed for studying the fast-ion physics on the large plasma device (LAPD). The source has been designed to match the ion beam speed with the Alfv\'{e}n speed in the LAPD plasma. The ion beam will be injected at a variety of pitch angles into the LAPD. The ion-beam source has an inductive RF source to produce $\approx 10^{19}$ m$^{-3}$ helium plasma in a ceramic dome (volume: $\approx 0.04$ m$^3$). The beam is accelerated using a rectangular (8 cm x 8 cm), multi-aperture, three-grid system. A pulsed DC power supply (25 kV, 4 A) has been developed to deliver the acceleration voltage to the grids during the time interval (0.1 -- 2.0 ms, rep rate: 1 Hz) of the beam injection. A EUV grazing incidence monochromator (for the Doppler-shift measurements) and Langmuir probes are main diagnostic tools. The source is presently being conditioned in a test facility. We plan to present the initial results on the characterization of the ion-beam and its interaction with the LAPD plasma.