  A meter-long, 23-liter EJ-309 liquid scintillator detector has been
constructed to study the light collection and pulse-shape discrimination
performance of elongated scintillator cells for the PROSPECT reactor
antineutrino experiment. The magnitude and uniformity of light collection and
neutron/gamma discrimination power in the energy range of antineutrino inverse
beta decay products have been studied using gamma and spontaneous fission
calibration sources deployed along the cell long axis. We also study
neutron-gamma discrimination and light collection abilities for differing PMT
and reflector configurations. Key design features for optimizing MeV-scale
response and background rejection capabilities are identified.
