The University Maryland Electron Ring (UMER)

Abstract

A detailed understanding of the physics of space-charge dominated beams is vital for many advanced accelerators that desire to achieve high beam intensity. In that regard, low-energy, high-intensity electron beams provide an excellent model system. The University of Maryland Electron ring (UMER), currently under construction, has been designed to study the physics of space-charge dominated beams with extreme intensity in a strong focusing lattice with dispersion. The tune shift in UMER will be more than an order of magnitude greater than exiting synchrotrons and rings. The 10-keV, 100 mA, UMER beam has a generalized perveance in the range of 0.0015, and a tune shift of 0.9. Though compact (11-m in circumference), UMER is a very complex device, with over 140 focusing and bending magnets. We report on the unique design features of this research facility, the beam physics to be investigated, and early experimental results.

Low-Energy-Spread Ion Bunches from a Trapped Atomic Gas

“…These nonlinear space charge effects play a decisive role in the beam formation for the most demanding applications such as heavy ion fusion, high-energy colliders, and free electron lasers. The only system at the moment fully dedicated to the study of such space charge effects is UMER [10,11], which employs a 10 keV electron beam in a ring.…”

Gridded Electron Guns and Modulation of Intense Beams

“…Fig. 3 shows current as a function of bias voltage measured on the University of Maryland Electron Ring gun [1], compared to a theoretical curve based on the ideal planar triode assumption [5]. For this test, the pulser voltage waveform remained unchanged but the bias voltage was varied.…”

“…These space charge forces can drive instabilities and inhomogeneities that can lead to emittance growth, coherent synchrotron radiation, and other disruptive phenomena, even after the beam becomes relativistic. Heavy ion fusion presents unique challenges, as it requires the propagation of intense [1] nonrelativistic beams over distances on the order of 1 -10 km [2]. These beams will be extremely susceptible to emittance growth and other difficulties associated with space charge waves launched from unintended modulation of the beam during generation and transport.…”

Longitudinal density modulation and energy conversion in intense beams

“…Such beams are referred to as intense [1]. The space charge and external focusing forces each consist of a transverse component perpendicular to the direction of travel, and a longitudinal component parallel to the direction of travel.…”