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The University of Maryland electron ring (UMER) is a low‐energy, high current recirculator for beam physics research with relevance to any applications that rely on intense beams of high quality. We review the space‐charge physics issues, both in transverse and longitudinal beam dynamics, which are currently being addressed with UMER: emittance growth and halo formation, strongly asymmetric beams, Montague resonances, equipartitioning, bunch capture and shaping, etc. Furthermore, we report on recent developments in experiments, simulations, and improved diagnostics for space‐charge dominated beams.

The University of Maryland Electron Ring (UMER) is a low energy, high current recirculator for beam physics research. Ring construction has been completed for multi‐turn operation of beams over a broad range of intensities and initial conditions. The electron beam current is adjustable up to 100 mA and pulse length as long as 100 ns. UMER is addressing issues in beam physics relevant to many applications that require intense beams of high quality, such as advanced concept accelerators, free electron lasers, spallalion neutron sources, and future heavy‐ion drivers for inertial fusion. The primary focus of this presentation is experimental results in the area of beam steering and control within the injection line and ring. Unique beam steering algorithms now include measurement of the beam response matrix at each quadrupole and matrix inversion by singular value decomposition (SVD). With these advanced steering methods, transport of an intense beam over 50 turns (3600 full lattice periods) of the ring has been achieved.

The University of Maryland Electron Ring (UMER) is built as a low‐cost testbed for intense beam physics for benefit of larger ion accelerators. The beam intensity is designed to be variable, spanning the entire range from low current operation to highly space‐charge‐dominated transport. The ring has been closed and multi‐turn commissioning has begun. One of the biggest challenges of multi‐turn operation of UMER is correctly operating the Y‐shaped injection/recirculation section, which is specially designed for UMER multi‐turn operation. It is a challenge because the system requires several quadrupoles and dipoles in a very stringent space, resulting in mechanical, electrical, and beam control complexities. Also, the Earth’s magnetic field and the image charge effects have to be investigated because they are strong enough to impact the beam centroid motion. This paper presents both simulation and experimental study of the beam centroid motion in the injection region to address above issues.

The University of Maryland Electron Ring (UMER), designed for transport studies of space‐charge dominated beams in a strong focusing lattice, is nearing completion. Low energy, high intensity electron beams provide an excellent model system for experimental studies with relevance to all areas that require high quality, intense charged‐particle beams. In addition, UMER constitutes an important tool for benchmarking of computer codes. When completed, the UMER lattice will consist of 36 alternating‐focusing (FODO) periods over an 11.5‐m circumference. Current studies in UMER over about 2/3 of the ring include beam‐envelope matching, halo formation, asymmetrical focusing, and longitudinal dynamics (beam bunch erosion and wave propagation.) Near future, multi‐turn operation of the ring will allow us to address important additional issues such as resonance‐traversal, energy spread and others. The main diagnostics are phosphor screens and capacitive beam position monitors placed at the center of each 200 bending section. In addition, pepper‐pot and slit‐wire emittance meters are in operation. The range of beam currents used corresponds to space charge tune depressions from 0.2 to 0.8, which is unprecedented for a circular machine.