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The MOLLER experiment proposed at the Thomas Jefferson National Accelerator Facility plans a precision low energy determination of the weak mixing angle via the measurement of the parity-violating asymmetry in the scattering of high energy longitudinally polarized electrons from electrons bound in a liquid hydrogen target (Møller scattering). A relative measure of the scattering rate is planned to be obtained by intercepting the Møller scattered electrons with a circular array of thin fused silica tiles attached to air light guides, which facilitate the transport of Cherenkov photons generated within the tiles to photomultiplier tubes (PMTs). The scattered flux will also pass through the light guides of downstream tiles, generating additional Cherenkov as well as scintillation light and is a potential background. In order to estimate the rate of these backgrounds, a gas-filled tube detector was designed and deployed in an electron beam at the MAMI facility at Johannes Gutenberg University, Mainz, Germany. Described in this paper is the design of a detector to measure separately the scintillation and Cherenkov responses of gas mixtures from relativistic electrons, the results of studies of several gas mixtures with comparisons to simulations, and conclusions about the implications for the design of the MOLLER detector apparatus. [ABSTRACT FROM AUTHOR]

Abstract: Enriched Xenon Observatory (EXO)-200 uses 468 large area avalanche photodiodes (LAAPDs) for detection of scintillation light in an ultra-low-background liquid xenon (LXe) detector. We describe initial measurements of dark noise, gain and response to xenon scintillation light of LAAPDs at temperatures from room temperature to 169K—the temperature of liquid xenon. We also describe the individual characterization of more than 800 LAAPDs for selective installation in the EXO-200 detector. [Copyright &y& Elsevier]

Abstract: The paper describes the design and performance of flux integrating Cherenkov scanners with air-core reflecting light guides used in a high-energy, high-flux electron scattering experiment at the Stanford Linear Accelerator Center. The scanners were highly radiation resistant and provided a good signal to background ratio leading to very good spatial resolution of the scattered electron flux profile scans. [Copyright &y& Elsevier]

SLAC E-158 is an experiment designed to make the first measurement of parity violation in Møller scattering. E-158 will measure the right-left cross-section asymmetry, ALRMøller, in the elastic scattering of a 45-GeV polarized electron beam from 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 photoemission-based polarized electron source requires 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), beamALR''s. This laser beam is produced by a unique SLAC-designed flashlamp-pumped Ti:Sapphire laser and is directed 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 beamALR''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 beamALR''s. We also present results on beam performance from engineering and physics runs for E-158. [Copyright &y& Elsevier]

Measurements of electron drift properties in liquid and gaseous xenon are reported. The electrons are generated by the photoelectric effect in a semi-transparent gold photocathode driven in transmission mode with a pulsed ultraviolet laser. The charges drift and diffuse in a small chamber at various electric fields and a fixed drift distance of 2.0 cm. At an electric field of 0.5 kV/cm, the measured drift velocities and corresponding temperature coefficients respectively are 1. 97 ± 0. 04 m m ∕ μ s and (− 0. 69 ± 0. 05) %/K for liquid xenon, and 1. 42 ± 0. 03 m m ∕ μ s and (+ 0. 11 ± 0. 01) %/K for gaseous xenon at 1.5 bar. In addition, we measure longitudinal diffusion coefficients of 25. 7 ± 4. 6 cm 2 /s and 149 ± 23 cm 2 /s, for liquid and gas, respectively. The quantum efficiency of the gold photocathode is studied at the photon energy of 4.73 eV in liquid and gaseous xenon, and vacuum. These charge transport properties and the behavior of photocathodes in a xenon environment are important in designing and calibrating future large scale noble liquid detectors. [ABSTRACT FROM AUTHOR]