Superconducting RF linear collider

A simulation is used to investigate the dependence of stability thresholds on the HOM (higher-order-mode) damping. The emittance growth and energy spread due to high-Q parasitic modes is computed as a function of bunch charge, loaded Q, and mode bandwidth. The HOM loading typical of a five-cell cavity with a pair of beam tube couplers is considered. It is found that a beam with bunch charge of 2*10/sup 10/ particles and bunch spacing of 100 ns accelerated to high energy in such a structure exhibits tolerable emittance growth. It is suggested that a 3-GHz superconducting linac can be incorporated very simply into a design for a high energy linear collider.<
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