A Beryllium Filter Spectrometer With High Efficiency for Neutron Inelastic Scattering

A beryllium filter detector spectrometer with high efficiency for neutron inelastic scattering has been built beside the horizontal channel of heavy water reactor in China Institute of Atomic Energy.It is the first time to develope a new type of beryllium filter with a wide receiving angle(～30°)and focus arrangement of beryllium blocks.The detecting efficiency of the spectrometer is raised at least by a factor of three.Furthermore,the influence of coherent scattering upon experiments has also been eliminated in the range of low energy.By automatic rotating of different crystal planes of Ge monochromator which possesses particular orientation the measurable energy range of the spectrometer has been widened(from 10 to 400meV)and the energy resolution improved (4%-9%).On this spectrometer,we have measured the optical vibrational modes for ZrH1.6 and PdH0.58 and the total spectrum of the high-temperature superconducting material YBa2 Cu3 O6+x and observed its unusual structural peaks, high frequency modes and anomalous scattering intensities.It has been shown that the spectrometer not only is efficient but also possesses an excellent physical capability.So it is possible to carry out extensive research on inelastic thermal neutron scattering on a medium-flux reactor.