"Zero-current" to extreme space-charge beam transport experiments on the University of Maryland Electron Ring (UMER)

Summary form only given. The University of Maryland Electron Ring (UMER), designed for transport studies of space-charge dominated beams in a strong focusing lattice, is nearing completion. UMER models, for example, the recirculator accelerator envisioned as a possible driver for heavy-ion inertial fusion. The UMER lattice consists of 36 alternating-focusing (FODO) periods over an 11.5-m circumference. The main diagnostics are phosphor screens and capacitive beam position monitors placed at the center of each 20/spl deg/ bending section. In addition, pepper-pot and slit-wire emittance meters are in operation. We present experimental results of beam transport over 2/3 of the ring, i.e. 24 FODO periods or 9.0 m, approximately, from the gun output. The range of beam currents, corresponding to space charge tune depressions from 0.2 to 0.8, is unprecedented for a circular machine. Issues associated with beam characterization, scaling of various parameters, alignment, rms envelope matching and halos are discussed.