Bonner sphere measurements in quasi-monoenergetic p-Li neutron fields of 243 and 387 MeV

Document available in abstract form only, full text of publication follows: This paper describes the results of neutron spectrometry using the Bonner Sphere Spectrometer (BSS ) at the ring cyclotron facility at the Research Centre for Nuclear Physics (RCNP), Osaka University, Japan. The BSS system consists of 15 polyethylene (PE) spheres with spherical 3He proportional counters in their centre. It also includes two PE spheres with lead shells inside, to increase their response to high-energy neutrons above 10 MeV. Quasi-monoenergetic neutron fields at RCNP were generated from a 10 mm thick Li target using the 7Li(p,n)7Be reaction, injected by 245 and 388 MeV protons. The neutrons produced at 0 deg. and 30 deg. were extracted into the time-of-flight (TOF) tunnel of 100 m length through the concrete collimator of 10 x 12 cm2 aperture and 150 cm thickness. The neutron energy spectra were measured at distance of 41 m from the target in the TOF tunnel. To deduce the energy spectra of neutrons from thermal to 1 GeV, an unfolding method with MSANB code was used together with response functions obtained by neutron transport calculations using the MCNP/LAHET code. The neutron energy spectra are discussed in terms of neutron fluence rates and ambient dose equivalent H*(10). The BSS results are also compared to neutron energy spectra measured by a NE213 organic liquid scintillator using the TOF method. (authors)