A 90° 3He Neutron Spectrometer

A fast 3He neutron spectrometer has been developed that is free of recoil spectrum effects. Positioning solid-state detectors outside the neutron beam at 90° results in this advantage and avoids nuclear reactions in the detectors themselves. Two modes of operation are examined: In conjunction with a pulse height analyzer, and in a high-event-rate, current-signal regime. The spectrometer was used in the latter mode to measure the neutron spectrum produced by a nuclear explosive in the Los Alamos time-of-flight neutron cross-section measurements. ¿ Present address: Rensselaer Polytechnic Institute, Troy, New York