PRECISION CONTROL OF INTENSE ELECTRON BEAMS IN A LOW-ENERGY RING

Abstract

Many applications of particle accelerators require beams with high intensity and low emittance in a stable fashion. An important research area involves the study of space-charge forces in beams, which are significant at low energy. Research reported in this dissertation was done on the University of Maryland Electron Ring (UMER), a particle accelerator designed for research on space-charge-dominated beams. High-precision control of space-charge-dominated beams is very challenging. However, standard beam control approaches do not work well on UMER. This is due to UMER's unique structure, in which there are fewer beam position monitors than beam position correctors and a complex coupling between the horizontal and vertical kicker magnets. In this work, a novel beam control algorithm was developed based on the closed-orbit response matrix, and this algorithm was applied to UMER. The algorithm markedly improves UMER's multi-turn operation while reducing closed orbit distortion. Using the orbit response matrix, a diagnosis method was developed that expeditiously detected malfunctions in components such as beam position monitors and magnets. Space-charge forces can greatly affect the resonant properties of rings. With the electrostatic particle-in-cell code WARP, ring resonances were analyzed under a variety of conditions. This resulted in an improved understanding of and capability to predict beam losses and improve machine performance. Simulation results using WARP were obtained for several magnet models and compared with results from other simulation codes. Experimental results on resonance analysis were also given using wall current monitor signals.