Conceptual design for a scintillating-fiber neutron detector for fusion reactor plasma diagnostics

A conceptual design for a ''pointing'' neutron detector that is capable of delivering 104--105 Hz countrate of T(D,n) events from triton burnup at a deuterium-burning tokamak is described. The detector consists of collimated bundles of scintillating fibers that are separated by metal or polyethylene. These bundles in turn are set into a larger collimator that has some of the bundles set in ''unplugged'' holes and others in ''plugged'' holes whose countrate difference gives the net countrate. It is computed that the use of a 6 MeVee (electron equivalent) discriminator will allow 14 MeV neutron countrates of 2x104 Hz in a DD machine or 3 MHz in a DT machine, while effectively rejecting the gamma background. The efficiency-area product for 14 MeV neutrons will be ∼0.014 cm2. The angular resolution is computed to be 4.5 degree HWHM for a 35-cm-long collimator