A SOURCE OF NEUTRON CAPTURE GAMMA-RAY WITH ENERGY TO 7 MeV AND TO 10 MeV BASED ON NEUTRON CALIBRATION FACILITY

Wide spread of technogenic sources of ionizing radiation such as particle accelerators and nuclear reactors leads to appearance of a number of applied metrological tasks aimed at providing spectrometric and dosimetric ionization measurement instruments, located in photon radiation fields with energy to 10 MeV. Gamma rays with energy higher 3 MeV may be acquired using radioactive thermal neutron capture on target, i.e. (n, γ)-nuclear reaction. Titanium is used in the range of energies to 7 MeV; nickel – to 10 MeV. A simplest source of instantaneous neutron capture gamma-ray should consist of fast neutron source, neutron moderator and a target irradiated with thermal neutrons. The collimator with thermal neutron geometry of АТ140 neutron calibration facility with ²³⁸Pu–Be fast neutron source may be used (IBN–8–6) as a source of gamma-ray with energy to 10 MeV. Monte-Carlo models of thermal neutrons geometry, facility and ²³⁸Pu–Be fast neutron source were built using MCNP–4b code. Energy distribution of flux density of neutron capture gamma–ray for titanium and nickel targets was defined. A spectrometric detector based on LaBr3(Ce) crystal Ø 38×38 mm with non-linear characteristics of channel-energy transformation in the range up to 10 MeV, was specifically manufactured for instrumental support of the experiment at SPE “ATOMTEX”. The results for Ti, Ni, and for bare ²³⁸Pu–Be neutron source were acquired. During the experiment a possibility to use neutron capture gamma-ray field formed by thermal neutrons geometry of АТ140 neutron calibration facility with ²³⁸Pu–Be-fast neutron source with Ti and Ni targets for calibration LaBr₃(Ce) spectrometers for energy to 10 MeV was confirmed. Closely stationing polyethylene plate in collimator channel provides significant increase in output of reference radiation from target simultaneously decreasing unneeded parts of the spectrum. 

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