RESPONSE FUNCTIONS OF THE 4-PI DETECTOR ORION TO 10-70 MEV NEUTRONS

The neutron detection performances of the 4 pi ORION counter were inve stigated with monoenergetic neutron beams delivered by the Louvain-la- Neuve facility. Two responses are supplied by such a counter: a prompt response, arising from the slowing down of neutrons within the liquid scintillator contained in the detector, and a delayed response corres ponding to the subsequent capture of the neutrons by Gd nuclei: with w hich the detector is loaded. Two experimental methods were used, allow ing one to probe the responses for different neutron energies. Despite the large size of the detector, the prompt response is observed to be very similar to that exhibited by small cells. For both responses, a reasonable overall agreement is found between the data and the predict ions of Monte-Carlo simulations. The timing resolution. of the order o f 3 ns, makes this detector suitable for time-of-flight methods in app lications requiring a high detection efficiency while accepting a mode rate energy resolution. (C) 1998 Elsevier Science B.V. All rights rese rved.