Calibration of Long Neutron Counter TETRA Using Reactions of Photo-Dissociation

TETRA long neutron counter has proven to be an unique tool to identify and to measure delayed neutron emission from photo-fission fragments produced at ALTO ISOL facility. TETRA uses robust technology based on 3He filled-counters operating in the proportional mode. The cross-section of the reaction (n, 3He) is very larger for the thermal neutron energy range. Thus, β-delayed neutrons are moderated and can be detected with a high efficiency. However, due to the moderation process, information on the initial neutron energy is typically lost. Energy of emitted neutrons is needed for detailed description of the process of delayed (multi) neutron emission from neutron rich nuclei. In the present paper we discuss one of a method which can be used to recover information on the initial neutron energy.