Alignment of the SLC Final Focus system using beam orbits

Abstract

Beam based alignment is being routinely applied in the SLC Final Focus and has proved to be a very useful tool for determining the quality of the zeroth order orbit as defined by various beam line elements. Given the stringent requirement on the beam quality at the interaction point, a well aligned beam line is essential in that it minimizes the confusion which would otherwise arise in the higher order optics, the demand called on the correctors which also serve as optical knobs, and the problem associated with the background radiation. In the SLC final focus we have been relying on an interplay between the field survey and the orbit analysis to achieve this purpose. Mechanical alignment generally provides coordinate information of various beam line elements and offset values inferred from these data and the model of the beam line. Beam based alignment is done mainly by recording the beam orbit under controlled experiment where optical elements or orbit conditions are varied. Due to the complexity of the beamline layout and special power supply configuration in the SLC Final Focus, the latter method is useful only when coupled with off-line analysis which disentangles the data taken at each measurement. In this report we describe the techniques used and the underlying principle, the procedure as applied in the Final Focus, the outcome of this exercise and some problems encountered. 6 figs