PBFA-II LITHIUM BEAM CHARACTERIZATION FROM INNER-SHELL X-RAY IMAGES

The Particle Beam Fusion Accelerator (PBFA II) is now driving targets with ICF-relevant lithium ion beams. During the most recent lithium beam target series, time-integrated x-ray pinhole cameras viewed the ion-induced inner-shell x-ray fluorescence from the central gold cone target and a titanium-coated strip. Ion-beam profiles at a nominal 10-mm radius and fixed azimuthal direction were obtained from images of the Ti Kα fluorescence of a Ti-coated Al diagnostic wire. The gold cone gave us beam profiles at a nominal 3-mm radius and at all azimuthal angles from the Au Lα fluorescence. From these profiles, we obtained the ion-beam vertical focus position, the full width at half maximum, and the degree of azimuthal uniformity for the lithium target shots. For these initial results, beam steering problems were evident. Azimuthal uniformity was measured from the ion-beam footprint on the outer Au case (predominantly Au α) of the hohlraum target and was found to be in the same range (up to 30%) as for previous proton beam target series. © 1995 American Institute of Physics.