New Post-Linac Collimation System for the Next Linear Collider

We present a new design for the NLC post-linac collimation system. The new design separates the collimation of off-energy particles and particles with large betatron amplitudes. The energy collimation system achieves passive protection against damage by an errant bunch train via large horizontal dispersion and vertical betatron functions, and makes use of optical symmetries to reduce jitter amplification. The betatron collimation system permits infrequent damage to the thin “spoiler” collimators, while the thick “absorber” collimators have a much larger aperture and are thus more difficult to hit. The physical phenomena which are relevant to the design and operation of the collimation system are reviewed, and the associated properties of the new system are discussed.