Influence of Bonner sphere response functions above 20 MeV on unfolded neutron spectra and doses

Calibration of a Bonner sphere spectrometer in quasi-monoenergetic neutron fields of 244 and 387 MeV

“…The other two response matrices were calculated with the GEANT4 code using the Bertini and the Binary intra-nuclear cascade models in the high-energy region, respectively. Differences in the calculated response functions of the BSS at energies above 20 MeV result in uncertainties of the unfolded fluence and dose rates of about 15% at high energies [6]. In order to calibrate the BSS, 246 MeV and 389 MeV proton beams were used at the RCNP cyclotron facility in Osaka, Japan, to generate quasi-monoenergetic neutron fields with peak energies of 244 and 387 MeV via 7 Li(p,n) 7 Be reactions.…”

“…Recently it was shown that for a typical energy distribution of secondary neutrons from cosmic radiation the differences in the response functions result in an uncertainty in the unfolded fluence rates at energies above 20 MeV of about 18% and, accordingly, a 13% uncertainty for the ambient dose equivalent rate [6]. The only way of determining which calculated response functions describe reality best is comparison to measurements performed in preferably quasi-monoenergetic neutron fields with known spectral fluence rate distribution.…”

NEUTRON RESPONSE FUNCTION OF BONNER SPHERE SPECTROMETER WITH 6LiI(Eu) DETECTOR

“…The MCNPX output are neutrons fluence on the 6 Monte Carlo codes for neutron transport calculations such as MCNPX crucially rely on input data cross sections that describe the interaction of neutrons with nuclei. For neutron energies below 20 MeV, experimental cross sections data are available that are validated against experimental data [16], while for neutron energies above 20 MeV experimental cross section data are scarce, therefore intra-nuclear cascade (INC) and evaporation models are usually applied in these Monte Carlo codes [17]. For this reason, every neutron transport code is based on theoretical nuclear models to describe interactions of neutrons with nuclei in matter [16].…”

“…For neutron energies below 20 MeV, experimental cross sections data are available that are validated against experimental data [16], while for neutron energies above 20 MeV experimental cross section data are scarce, therefore intra-nuclear cascade (INC) and evaporation models are usually applied in these Monte Carlo codes [17]. For this reason, every neutron transport code is based on theoretical nuclear models to describe interactions of neutrons with nuclei in matter [16]. The calculation of BSS response functions using the Monte Carlo code and nuclear models may increase the uncertainty, in particular for neutron energies above 20 MeV [17], [18].…”

Characterization of extended range Bonner Sphere Spectrometers in the CERF high-energy broad neutron field at CERN

“…Specific calculations have been carried out to assess the code-to-code variability in determining the response function of an ERBSS [22]. Simulation codes have been compared with experimental data on neutron production from targets at different energies and angles [23,24].…”