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

T. B. Humensky; R. Alley; A. Brachmann; M. J. Browne; G. D. Cates; J. Clendenin; J. deLamare; J. Frisch; T. Galetto; E. W. Hughes; K. S. Kumar; P. Mastromarino; J. Sodja; P. A. Souder; J. Turner; M. Woods

doi:10.1016/j.nima.2003.09.065

arXiv · physics/0209067

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

T. B. Humensky·R. Alley·A. Brachmann·M. J. Browne·G. D. Cates·J. Clendenin·J. deLamare·J. Frisch·T. Galetto·E. W. Hughes·K. S. Kumar·P. Mastromarino·J. Sodja·P. A. Souder·J. Turner·M. Woods

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Abstract

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_LR^Moller, 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 ~10^-7 to an accuracy of better than 10^-8. 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 A_LR's. This laser beam is produced by a unique SLAC-designed flashlamp-pumped Ti:Sapphire laser and is propagated through a carefully designed set of polarization optics. We analyze the transport of nearly circularly polarized light through the optical system and identify several mechanisms that generate ^beam A_LR's. We show that the dominant effects depend linearly on particular polarization phase shifts in the optical system. We present the laser system design and a discussion of the suppression and control of ^beam A_LR's. We also present results on beam performance from engineering and physics runs for E-158.

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T. B. Humensky, R. Alley, A. Brachmann, M. J. Browne, G. D. Cates, J. Clendenin, J. deLamare, J. Frisch, T. Galetto, E. W. Hughes, K. S. Kumar, P. Mastromarino, J. Sodja, P. A. Souder, J. Turner, M. Woods. 2002-09-19. SLAC's Polarized Electron Source Laser System and Minimization of Electron Beam Helicity Correlations for the E-158 Parity Violation Experiment. https://doi.org/10.1016/j.nima.2003.09.065

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