Characterisation of a neutron experimental station at the Lund Ion Beam Analysis Facility

Abstract: At the 3 MeV light ion accelerator of the Lund Ion Beam Analysis Facility (LIBAF), a beamline is about to be constructed with the purpose of producing neutrons as a higher yield complement to the current Source-Testing Facility. When operational, the beamline will provide the possibility of tagging both thermal and fast neutrons. These neutrons will be used to test and characterise new available materials to improve future detector systems. In this thesis, evaluations of three aspects of accelerator-based neutron production are presented: high yield neutron producing reactions and their related target materials, effective moderators as well as lower yield neutron producing materials to be used in a beam dump. The evaluations are based on literature studies, calculations and an experiment conducted at LIBAF in the late fall of 2017. The thesis is to serve as a decision basis for the construction of the coming beamline. The results of the evaluation indicated that the use of two different targets will be beneficial for the coming beamline. The use of a beryllium target with impinging deuterons will result in the highest yield of neutrons for the considered reactions. The reaction 9^Be(d,n){10}^B is suitable for producing neutrons which are to be tagged using a deflector system. A second target of tritiated titanium (TiT_x) will be required if the facility is to provide fast coincidence measurements with the neutron and the recoil of the T(d,n)4^He reaction. The feasibility of LIBAF of providing tagged fast neutrons with a target of tritium was demonstrated. For the thermalisation of the created neutrons, suitable moderators were found to be both hydrogenous or deuterated materials. Which material to choose will depend on if a higher thermal flux is prioritised over a higher brilliance. Simulations to optimise a suggested moderator design will be required. Materials which are to be considered for the use in a beam dump at LIBAF are required to result in a low yield of neutrons for incoming protons or deuterons. This is to reduce the activation of the material and to reduce the background. Both gold and tungsten were found to be beneficial. For a final decision thereof, simulations related to the activation of these materials will be required.