SLAC's Polarized Electron Source Laser System and Minimization of Electron Beam Helicity Correlations for the E-158 Parity Violation Experiment

摘要

SLAC E-158 is an experiment designed to make the first measurement of parity violation in Moller scattering. E-158 will measure the right-left cross-section asymmetry, A (sup Moller) (sub LR), in the elastic scattering of a 45-GeV polarized electron beam off unpolarized electrons in a liquid hydrogen target. E-158 plans to measure the expected Standard Model asymmetry of approximately 10 to the minus 7th power to an accuracy of better than 10 to the minus 8th power. To make this measurement, the polarized electron source requires for operation an intense circularly polarized laser beam and the ability to quickly switch between right- and left-helicity polarization states with minimal right-left helicity-correlated asymmetries in the resulting beam parameters (intensity, position, angle, spot size, and energy), beam ALR's.