Proton-recoil detectors for time-of-flight measurements of neutrons with kinetic energies from some tens of keV to a few MeV

For experiments at the superconducting electron accelerator ELBE, where neutrons in the kinetic energy region from some tens of keV to a few MeV will be produced by bremsstrahlung, neutron-time-of-flight detectors have been developed. These detectors are made from the plastic scintillator material EJ-200. Efficiency calibration showed more than 10% efficiency for kinetic energies down to 30 keV. The calibration was done at the “accelerator facility for fast neutron research” at Physikalisch-Technische Bundesanstalt in Braunschweig, using pulsed quasi-monoenergetic neutron fields with a well-determined fluence. The low detection threshold was obtained by coincident readout of two Hamamatsu R2059-01 photomultiplier tubes per scintillator and by triggering just below the single-photo-electron peak of these photomultiplier tubes, which additionally gives a well-reproduceable detection threshold.