A spectrometer for measurement of the neutron capture gamma multiplicity at a stationary research reactor

Abstract The multiplicity spectrometry technique of secondary emission of nuclei excited by thermal neutrons for the neutron cross sections measurements is developed. A multisectional NaI(Tl) scintillation detector for gamma-ray detection with high efficiency and 4π-geometry is used. The experiments are performed on a stationary 2 MW research reactor by the time-of-flight method. Such a method and apparatus are also to be used to measure the important neutron constant “alpha” (capture-to-fission ratio) for 235 U.