Calculations of Multiplicity and Efficiency from Neutron Capture in the Rpi Multiplicity Detector.

Calculations employing the single particle model and Monte Carlo transport of neutron capture gamma rays from holmium and erbium have been performed. Various hindrance factors were applied to Weisskopf transition probabilities. A statistical model of the nucleus was used for excitation energies above 1-2 MeV. Measured branching ratios were used for low-lying energy level transitions. Results of detector efficiency and multiplicity calculations were compared to data from the Rensselaer Polytechnic Institute 16-segment multiplicity detector. Different hindrance factors are recommended based on multiplicity data and isomeric state populations in holmium and erbium. Sensitivity of multiplicity to experimental energy thresholds and distinguishability of elements, isotopes, and spin states are discussed. The analysis confirms collective effects, i.e. enhanced electric quadrupole transition rates in holmium and erbium. The variation of detector efficiency with binding energy, hindrance factors, and detection energy thresholds are presented. Detector efficiency vs incident neutron energy with a^{10}B_4 C sample in the detector is calculated.