Some Improvements in a Neutron Time-of-Flight Spectrometer for D+T Neutrons

Some improvements in a neutron time-of-flight spectrometer using the associated particle method are described. A simple circuit is devised to compensate the dependence of the flight-time of neutrons of a given energy on the pulse height of the output signals of the neutron detector. By the use of this circuit in the time-of-flight spectrometer having been used in this laboratory a time resolution of 1.2 nsec (f.w.h.m.) is obtained for direct neutrons from the D+T source. The spectrometer system is also so improved that two neutron detectors operate together with a single set of circuits for n-γ discrimination and time-to-pulse height conversion. The effects of the shadow bar and detector shielding on the background level are studied. The background is reduced by an order of magnitude by the use of a suitable shadow bar and detector shield.