A thermal-neutron source for calibration of "zero-thickness" detectors

A specialized source of thermal neutrons was produced on the basis of the BP-K1 research reactor. The thermal-neutron field characteristics were determined in the presence of intermediate and fast neutrons. The neutron spectrum is presented in analytical form in the 10(-10)-18-MeV energy range. In the maximum single energy run of the reactor with a duration of <2 min, the thermal-neutron fluence was 1.9 x 10(14) neutron/cm(2), with fluences of intermediate and fast neutrons of 0.4 x 10(14) and 0.3 x 10(14) neutron/cm(2), respectively. The effective temperature of thermal neutrons is 6.6 degrees C higher than the ambient temperature. The fraction of the field isotropic component is estimated as 80%.