Effects of quadrupole rotations on the transport of space-charge-dominated beams: theory and simulations comparing linacs with circular machines

Abstract

PIC-code simulation results are presented where a space-charge-dominated beam is transported in a lattice with quadrupole rotation errors. Two examples are studied in detail: the circular lattice for the University of Maryland Electron Ring (UMER) and the straight lattice from an early design of a proposed heavy ion inertial fusion (HIF) research experiment known as the Integrated Research Experiment (IRE). Reasonably small errors have little effect. However, the dependence on the strength of the errors is nearly quadratic. Slightly larger errors, therefore, can cause deterioration in beam quality, as manifest by a large increase in beam emittance and formation of a halo, leading eventually to particle losses. The simulations are accompanied by the moment equations for such a system in the presence of beam acceleration.