Performance and design study of a directional scintillating fiber detector for 14-MeV neutrons using GEANT

Abstract

A directional scintillating fiber detector for 14-MeV neutrons was simulated using the GEANT4 Monte Carlo simulation tool. Detail design aspects of a prototype 14 MeV neutron fiber detector under development were used in the simulation to assess performance and design features of the detector. Saint-Gobain produced, BCF-12, plastic fiber material was used in the prototype development. The fiber consists of a core scintillating material of polystyrene with 0.48 mm × 0.48 mm dimension and an acrylic outer cladding of 0.02 mm thickness. A total of 64 square fibers, each with a cross-sectional area of 0.25 mm² and length of 100 mm were positioned parallel to each other with a spacing of 2.3 mm (fiber pitch) in the tracking of 14-MeV neutron induced recoil proton (n-p) events. Neutron induced recoil proton events, resulting energy deposition in two collinear fibers, were used in reconstructing a two dimensional (2D) direction of incident neutrons. Blurring of recoil protons signal in measurements was also considered to account uncertainty in direction reconstruction. Reconstructed direction has a limiting angular resolution of 3° due to fiber dimension. Blurring the recoil proton energy resulted in further broadening of the reconstructed direction and the angular resolution was 20°. These values were determined when incident neutron beam makes an angle of 45 degree relative to the front surface of the detector. Comparable values were obtained at other angles of incidence. Results from the present simulation have demonstrated promising directional sensitivity of the scintillating fiber detector under development.