Development of a neutron detector for A1/KAOS@MAMI

Abstract

on behalf of the A1 collaboration With the A1/KAOS spectrometers at the Institut fur Kernphysik in Mainz high precision experiments are performed to investigate the structure of the nucleus and its constituents. So far the knowledge of the neutron form factor (FF) is limited because of poor detection efficiencies. The novel neutron detector aims for a neutron detection efficiency better than 80 %. Leading to smaller systematic uncertainties, it should be possible to improve measurements of the neutron electric FF, especially in the low momentum tranfer range Q 2 = 0.2 1.5 GeV 2 . In addition the new detector opens the possibility to study non-mesonic two-body weak decays. The concept of the detector foresees a modular concept with an active detector volume of about one cubic meter. To allow for high beam currents and the resulting high rates, the detector will be highly segmented using 48 crossed layers consisting of 48 bars with the dimension (20 x 20 x 960) mm 3 . In total 4608 channels have to be read out via WLS fibers using silicon multipixel photon counters (MPPC). Performing a GEANT simulation, where the crossed layer geometry of the detector is taken into account, a spatial resolution of less than 1.5 cm (FWHM) and timing resolution of less than 0.5 ns is achievable. Several scintillator materials like liquids, solids or extrusions together with different WLS fibers have been tested and compared. The results from first prototype tests are presented.