Characterization of E158 Beam

Abstract

Stanford Linear Accelerator Center (SLAC) parity violation experiment E-158 uses a high intensity electron beam accelerated to either 45GeV or 48GeV in the SLAC Linac and requires a small energy spread, small off axis position motion, and low jitter. The purpose of our research was to better quantify the current values of energy, intensity, and position jitter as well as the relations between them and to further the understanding of the beam dynamics involved. Specifically, our method was to take data on a series of pulse lengths shorter than the experimental beam to gain information about the length dependence of the different beam parameters, effectively enabling us to create jitter, position, and energy profiles of the beam. Position was measured by beam position monitors (BPMs), intensity was measured by toroids, and energy was measured by a Synchrotron Light Monitor (SLM) as well as several energy BPMs. Data was collected using the SLAC Control Program (SCP) and analyzed using Matlab. Position jitter was found to, in general, increase linearly (10microns per 50ns) with pulse length. The peak to peak energy difference across each pulse is currently about 0.4% of the total energy, with the RMS energy jitter usually ranging from 0.013%more » to 0.10% for the different pulse lengths. Intensity jitter had no discernable correlation with pulse length. The slope of the linear relation between energy and intensity (beam loading relation) varied significantly with pulse length as well as with the method used to extract energy data. The position, intensity and energy profile data agree qualitatively with accepted theories and provide a more encompassing picture of the beam dynamics for E-158. The same is true, to a lesser extent, for the energy jitter and beam loading data, although some results here were unexpected.« less