Neutron to Gamma Pulse Shape Discrimination in Liquid Argon Detectors with High Quantum Efficiency Photomultiplier Tubes

A high Light Yield Liquid Argon chamber has been radiated with an Am/Be source for signal-to-background separation level characterization in a Dark Matter Liquid Argon based detector. Apart from the standard nuclear recoil and electron events, from neutron elastic interactions and gamma conversions respectively, an intermediate population has been observed which is attributed to inelastic neutron scatters on Argon nuclei producing Argon recoil and simultaneous gammas from nuclear de-excitation. Taking account of these events results in a better determination of the recoil-like to electron-like separation based on the shape of the scintillation pulse. The results of this recent study as well as from a previous study with a chamber with a lower Light Yield are presented. (C) 2012 Published by Elsevier B. V. Selection and/or peer review under responsibility of the organizing committee for TIPP 11.