Measurement of the Effect of Collimator Generated Wakefields on the Beams in the Slc *

Collimators with adjustable jaws are used in the SLC linac, arcs, and final focus to eliminate the tails of the beams that produce backgrounds in the SLD detectors. However, if the beams are not centered within the jaws of the collimators, transverse wakefields are generated which act to increase the beam emittances. The sensitivity to the beam offset is largest in the vertical collimators in the linac where the small beam sizes (< 100 pm) require that the gap between the jaws be reduced to about a millimeter for effective background reduction. GL4 lb