A DIRECTIONAL FAST-NEUTRON DETECTOR USING SCINTILLATING FIBERS AND ANINTENSIFIED CCD CAMERA SYSTEM

We have been developing and testing a scintillating fiber detector (SF D) for use as a fast neutron sensor which can discriminate against neu trons entering at angles non-parallel to the fiber axis (''directional ity''). The detector/convertor component is a fiber bundle constructed of plastic scintillating fibers each measuring 10 cm long and either 0.3 mm or 0.5 mm in diameter. Extensive Monte Carlo simulations were m ade to optimize the bundle response to a range of fast neutron energie s and to intense fluxes of high energy gamma-rays. The bundle is coupl ed to a set of gamma-ray insenitive electro-optic intensifiers whose o utput is viewed by a CCD camera directly coupled to the intensifiers. Two types of CCD cameras were utilized: 1) a standard, interline RS-17 0 camera with electronic shuttering and 2) a high-speed (up to 850 fra me/s) field-transfer camera. Measurements of the neutron detection eff iciency and directionality were made using 14 MeV neutrons, and the re sponse to gamma-lays was performed using intense fluxes from radioisot opic sources (up to 20 R/h). Recently, the detector was constructed an d tested using a large 10 cm by 10 cm square fiber bundle coupled to a 10 cm diameter GEN I intensifier tube. We present a description of th e various detector systems and report the results of experimental test s.