Neutron spectrum measurements at a 40-MeV proton cyclotron.

: A set of seven activation reactions has been selected for neutron spectral analysis in the environment of a proton-cyclotron target. This choice of reactions: 59Co(n, p) 59Fe, 59Co(n, 2n) 58Co, 59Co(n, 3n) 57Co, 197Au(n, gamma) 198Au, 197Au(n, 2n) 196Au, 197Au(n, 4n) 194Au, 27Al(n, alpha) 24Na, analyzed by means of a Ge(Li) detector, reduces to a minimum of three the number of activation detectors employed, and makes possible convenient and accurate spectral measurements to at least 40 MeV. Criteria for selection of the activation materials from a list of candidates are discussed. A detailed comparison of the unfolding programs LYRA and SAND is made, and reasons are given for our choice of SAND in our application. Spectra of neutrons emitted at 0 degrees, 45 degrees and 90 degrees from thick targets of A1, Fe, Cu, Ta and stainless steel, irradiated by 40-MeV protons at the Milan AVF cyclotron, using the analysis technique described, are given and discussed.