A comparison of neutron detection systems with radioisotopic neutron sources in preparation for characterization of the neutron sepctra of varian model 2100 and 2300 clinacs(registered trademark)

This paper reports on a comparison of the performance of three different methods of neutron detection/spectrometry:moderated indium foil activation, the Bonner multisphere spectrometer with {dollar}sp6{dollar}LiF and {dollar}sp7{dollar}LiF thermoluminescent dosimeters, and the bubble detector spectrometer (BDS). A {dollar}sp{lcub}252{rcub}{dollar}Cf neutron source was used for this purpose. These data were analyzed to ascertain which method provided the "best fit" of the {dollar}sp{lcub}252{rcub}{dollar}Cf fission spectrum as determined by concordance with reference values. The BUNKI program was used to unfold the data from the Bonner multispheres and the BDS. Spectral stripping was also applied to the BDS data. The method given in American Association of Physicists in Medicine Report 19, National Council for Radiation Protection Report 79, and LaRiviere were used for the moderated foils. Variations in the sensitivity of the BDS were checked with a {dollar}sp{lcub}238{rcub}{dollar}PuBe radioisotopic neutron source at intervals throughout the course of the study.; Final results indicate that the Bonner multisphere system is the "better" of the three neutron detection methods, although the method is not without problems. The moderated foil method closely agreed with the reference values, but cannot provide spectral distribution data. The BDS data were subject to oscillations imposed by the non-negativity conditions in spectral stripping.