Calculation of particle motions at the head and tail of a bunch for the University of Maryland electron ring

Abstract

The end effect in a bunched beam is caused by the space-charge forces, which accelerate particles at the bunch head and decelerate particles at the bunch tail. It occurs in high-current linear accelerators and rings [1]. In the University of Maryland Electron Ring (UMER) project [2,3,4], the energy of particles at the very ends of a rectangular bunch is 15% different from that of the main part of the bunch. Assuming a negligible transverse space charge effect at the edge of the bunch, one dimensional single particle calculation is performed by a matrix formalism [6] to estimate the ratio of particle loss due to the end effect. Two possible cases are examined: with no induction gap, and with three induction gaps. If three induction modules are used, for a small number of turns, the particle loss is less than 0.15%, which is small enough to be acceptable. Simulation by code CIRCE [8] is in progress.

The Maryland electron ring for investigating space-charge dominated beams in a circular fodo system

“…There are 15 diagnostic parts containing capacitive BPMs [4] and phosphor screens; three induction modules provide fast-rising "ear fields" to prevent expansion of the bunch ends [5] and acceleration in a future extension of ring operation. The electron bunch is injected into the ring at a repetition rate of 60 Hz or less from the injector system [3] with the help of two pulsed Panofsky quads [6] and a pulsed dipole.…”