Design of a Compact 4.PI. Ge Spectrometer for the Measurement of Neutron Capture Cross Sections of Minor Actinides

A compact 4π Ge spectrometer was designed for the measurement of neutron capture cross sections of minor actinides. It consists of two EUROBALL clusters and four clover detectors with BGO shields surrounding a sample as close as possible so as to absorb a few γ-rays of high energy emitted after the neutron capture reaction with reasonable efficiency. This feature opens up the possibility to discriminate the desired nuclide from other impurities based on the measurement of excitation energy and determine the cross section accurately. Overall performances such as total detection efficiencies for 3 cascade γ-rays as well as monochromatic γ-rays were simulated using Geant4. It turned out we could achieve the peak detection efficiency as large as 0.9% for 3 cascade γ-rays, which is almost an order of magnitude larger than the value of the Gammasphere.