Summary form only given. The extremely fast /spl sim/3 ns rise-time of the TriMeV voltage pulse is ideal for studying beam transport issues. A series of radiographic source optimization experiments planned in collaboration with Sandia National Laboratories will investigate different diode configurations to reduce the radiographic spot size. Both ballistic propagation and non-neutralized transport, where the self-fields pinch the beam, will be studied. A magnetically-immersed diode, where a mm-diameter electron beam is launched from a needle cathode and confined in a /spl sim/12 T solenoidal magnetic field during acceleration to the target in vacuum, will also be studied. This immersed diode previously demonstrated <2-mm spots on the Hermes III accelerator. It is anticipated that similar results will be attained on TriMeV. A review of the operating parameters, geometry, and electrical characteristics will be presented along with an outline of the experimental program and a description of the diode and transport configurations studied. The most recent shot data will also be presented with an emphasis on the results from the immersed diode experiments.