Experimental analysis of neutron and background gamma-ray energy spectra of 80-400 MeV 7Li(p,n) reactions under the quasi-monoenergetic neutron field at RCNP, Osaka University

Yosuke Iwamoto,Masayuki Hagiwara,Tatsuhiko Sato,Akihiko Masuda,Hiroshi Yashima,Tetsuro Matsumoto,Hiroshi Iwase,Daiki Satoh,Takashi Nakamura,Tatsushi Shima

doi:10.1051/epjconf/201715308019

Abstract

To develop the 100-400 MeV quasi-monoenergetic neutron field, we measured neutron and unexpected gamma-ray energy spectra of the 7 Li(p,n) reaction with 80-389 MeV protons in the 100-m time-of-flight (TOF) tunnel at the Research Center for Nuclear Physics (RCNP) cyclotron facility. Neutron energy spectra with energies above 3 MeV were measured by the TOF method, which had been reported in our previous papers, and photon energy spectra with energies above 0.1 MeV were measured by the automatic unfolding function of the radiation dose monitor DARWIN. For neutron spectra, the contribution of peak intensity to the total intensity integrated with energies above 3 MeV varied between 0.38 and 0.48 in the proton energy range of 80–389 MeV. For gamma-ray spectra, highenergetic gamma-rays at around 70 MeV originated from the decay of π0 were observed with proton energies higher than 200 MeV. For the 246-MeV proton incident reaction, the contribution of gamma-ray dose to neutron dose is negligible because the ratio of gamma-ray dose to neutron dose is 0.014.

Highlights

The expected neutron fluence spectra in such as highenergy particle accelerators and flight altitudes environments typically have a peak at approximately 100 MeV, with maximum energies reaching the GeV range
We reported measurements of gammaray energy spectra and doses in the Research Center for Nuclear Physics (RCNP) quasimonoenergetic neutron field
The peak neutron energy is lower than the proton energy because of energy loss in the lithium target, and it is lower than the 1.88 MeV threshold energy of the 7Li(p,n) reaction

Summary

Introduction

The expected neutron fluence spectra in such as highenergy particle accelerators and flight altitudes environments typically have a peak at approximately 100 MeV, with maximum energies reaching the GeV range. For development of high-energy neutron monitors employed in these environments, it is important to calibrate instruments in well-defined high-energy monoenergetic neutron fields during response validation. In the high-energy neutron field, it is important to assess the contribution of high-energetic gamma-rays generated from π0 decay. One should note that Fermi motion of nucleons allows for π0 production even at energies below 290 MeV [11]. It is important for calibration of radiation monitors to characterize neutron spectra and high-energy gamma-ray spectra in the high-energy neutron field

Methods

Results

Conclusion