Electron beam injection, deflection, and transport in the UNM betatron

The authors present results from recent experiments on the generation of high-power relativistic electron beams using an upgraded injector and subsequent injection and transport of the beams in the UNM (University of New Mexico) betatron. The experiments described were performed with peak beam energies of about 420 keV. The electron beams were deflected onto the main axis of the accelerating ring using a transverse electrostatic field. The dependence of transported beam current on both the vertical and focusing magnetic field strengths is discussed. The electron beam injector was upgraded to double the original peak voltage. The inclusion of a novel crowbar has resulted in an 80-ns pulse length with injector voltage being constant within 4%. Transport studies have indicated that about 30 A of current is measured after the first curved section of the ring, but that an appreciable number of electrons are lost in propagating around the system. Optimizing the matching of the beam leaving the transport tube with the focusing field of the accelerating ring should allow for improvements in beam transport efficiency