Development of an encapsulated scintillating fiber detector as a 14-MeV neutron sensor

A scintillating fiber detector has been developed and tested for use as a 14-MeV neutron sensor. The detector, designated an ''Encapsulated Scintillating Fiber Detector (EFD)'', is composed of a parallel array of 0.5 x 0.5 x 15 mm BCF-12 plastic scintillating fibers encapsulated in clear BC-600 optical cement. The 85 fibers form a 12 x 12 mm square array, with a separation gap of 0.8-1 mm, in the center of the 40 mm diameter x 15 mm thick hardened optical cement. It can be directly coupled to an ordinary 2 in. diameter photomultiplier tube and its simple electronics. The response of the detector to gamma-rays from isotopic sources, as well as to 2.6- and 14-MeV monoenergetic neutrons from a neutron generator has been evaluated. The detector shows 3 distinct properties simultaneously, i.e. (1) good gamma-ray pulse height reduction, (2) discrimination against 14-MeV neutrons entering at angles non-parallel to the fiber axis, and (3) production of a full energy peak of 14-MeV recoil protons in the direction of the fiber axes. Investigations by Monte Carlo simulation are also included. (orig.)