14 MEV NEUTRON-SPECTRA MEASUREMENTS WITH 4-PERCENT ENERGY RESOLUTION USING A TYPE-IIA DIAMOND DETECTOR

A natural diamond detector has been used as a neutron spectrometer to measure 14 MeV neutron spectra produced by a neutron generator. The spectrometer chain was energy calibrated with a Am-241 alpha source; a resolution of 1.6% FWHM was observed. The C-12(n,alpha(0))Be-9 reaction which occurs in diamond was used to measure the neutron spectra and the measured energy resolution at FWHM was 4%. The detection efficiency was found to be a factor 2.5-3.5 times lower than expected. These results could be interpreted as the consequence of a loss of counts in the peak due to the mean charge collection distance of the bulk of the detector, which was determined to be d(c) = 71 +/- 18 mu m Moreover, a novel technique which employs fast neutron interrogation has been used to determine the bulk charge collection distance in diamond; this technique could be used also with other materials.