Existing accelerators are substantially constrained by space charge forces within the beam, which if not properly controlled, can lead to deleterious effects such as emittance growth, instabilities, and halo formation.  These effects limit the number of particles that can be transported in a given phase space volume, ultimately impacting the brightness and luminosity of the machine.  At the University of Maryland Electron Ring (UMER) Facility, we employ a number of low-energy electron experiments designed to deliberately enhance space charge effects, in order to shed light on these issues and learn how to better control and manage space charge effects in beams.  The centerpiece of our laboratory is the Electron Ring, a small-scale (4-m diameter) recirculator transporting up to 100 mA of 10 keV electrons, or about 10 nC per a 100-ns pulse.  When scaled to energies and parameters comparable to the ILC or the SNS, for instance, the UMER beam correspondingly possesses orders of magnitude more space charge.  This beam intensity and the density and quality of the UMER diagnostics and simulation support place our lab at the forefront of understanding space charge dynamics.

In addition to UMER we have a separate experiment, the Long Solenoid Experiment (LSE) for offline development of diagnostics, such as a high-resolution energy analyzer, and for exploring longitudinal dynamics in beams and energy spread evolution.  This work is closely coupled with a program on free electron lasers and photocathode development.  All these experiments are augmented by a superb computer simulation capability closely coupled with the experimental program.  The main computational workhorse is the PIC code WARP, developed at LLNL/NRL [Grote, et al., Fus. Eng. Des 32-33, 1996] and extensively benchmarked on our experiments. 

Altogether, this valuable investment from the US DOE enables a large number of students to carry out cutting-edge experiments of relevance not only to existing and future high-energy machines but also to many other emerging applications of high-brightness beams, such as spallation neutron sources and free-electron lasers.