Longitudinal phase space setup for the SLC beams

The longitudinal phase space distribution of the SLC beams is affected by many different machine parameters and constraints. By using a technique of over-compression in the ring to linac transfer line, a small energy spread of 0.12% can be achieved at the end of the linac for a bunch length of 1.2 mm (σ). In the final focus a small energy spread is desirable to reduce emittance dilution due to chromatic effects. Optimization of the bunch length is also important as a longer bunch of 1.2 mm can contribute up to 40% luminosity enhancement due to disruption. If there is a correlated energy variation along the bunch, for example due to mistuning of the optimal rf phase with respect to the beam, the bunch will be further compressed as it passes through the SLC Arcs. The resulting bunch can be too short to produce the desired disruption enhancement, but will radiate more beamstrahlung during collisions giving a false indication of higher luminosity. This paper discusses the interplay of these issues from the damping ring to the interaction point