Designing a Neutron Detector With Improved Position Resolution for the MoNA Collaboration

The investigation of neutron-unbound states at the drip line using invariant mass spectroscopy depends critically on the measurement of the four-momentum vector of the emitted neutrons. Most current large-area neutron detectors rely on plastic scintillator bars with a pair of photo-multiplier tubes (PMTs) at the ends to deduce the position of the emitted light from a time difference measurement of the PMT signals. This results in a limited position resolution of the order of centimeters. A different option is to localize the light emission using discrete or position sensitive photo detectors. Arrays of SiPM detectors or photo-sensitive THGEMs could be utilized. In this study possible geometries for such an approach are investigated regarding their position resolution and light collection efficiencies. For this purpose Geant4 simulations are being performed and tests with protoype detectors are planned.