The trajectory control in the SLC linac

In order to maintain a small emittance at the end of the linac, the tolerance on the trajectory deviations become tighter when the beam intensities increase. The existing two-beam trajectory correction method works well when the theoretical model agrees with the real machine lattice. Unknown energy deviations along the linac as well as wake field effects can cause the real lattice to deviate from the model. This makes the trajectory correction difficult. Several automated procedures have been developed to solve these problems. They are: an automated procedure to frequently steer the whole linac by dividing the linac into several small regions, an automated procedure to empirically correct the model to fit the real lattice, and eight trajectory-correcting feedback loops along the linac and steering through the collimator region with restricted corrector strengths and a restricted number of correctors.<>