Neutron-induced partial gamma-ray cross-section measurements with GEANIE at LANSCE/WNR

GEANIE is the first large-scale Ge detector array used in conjunction with a high-energy neutron spallation source. GEANIE consists of eleven Compton-suppressed planar detectors, nine suppressed and six unsuppressed co-axial detectors. Spallation neutrons are provided by the LANSCE/WNR facility, and reaction neutron energies are determined via time-of-flight. Neutron flux is monitored in-beam with a fission chamber. GEANIE at LANSCE/WNR currently emphasizes the measurement of partial gamma-ray cross sections as a function of neutron energy. Absolute cross section measurements require a complete understanding of array performance. Important effects include intrinsic detector efficiency, beam and detector geometry corrections, target attenuation, and deadtime. Measurements and calculations of these effects will be presented for the specific cases of iron and actinide targets. The use of radioactive targets incurs a large deadtime penalty. In order to increase data throughput we are making plans to move to a triggerless data acquisition system. These modifications and other improvements to the electronics for better timing will be discussed.