Beam-Based Determination of the Offset of Booster gamma-T Quads

Twelve pulsed gamma-T quads have been installed in the Booster to provide fast transition crossing. The less time the beam stays in the non-adiabatic period near transition, the less the longitudinal emittance grows. From the past experience, the gamma-T quads are not well aligned relative to the usual closed orbit. Quad steering can cause beam loss and a dispersion wave after transition. To make the gamma-T quads routinely operational, procedures for finding the center of the beam relative to the quads and centering the beam through all of them are very important. A program, which uses the difference in the closed orbits when gamma-T quads are on and off and calculates the offsets of the beam relative to gamma-T quads, has been developed and tested. A radial orbit offset (ROF) of about 3 mm has been experimentally determined to be nearly the optimal radial position for centering the beam through all the gamma-T quads, thereby eliminating the immediate need for repositioning the quads.