A dual-detector extended range rem-counter

The design and characterization of a dual-detector spherical rem counter is discussed in this paper. The rem counter is based on a polythene sphere with lead and cadmium insets, designed to host at its centre either an active (3He SP9 proportional counter) or a passive (CR39 + 10B radiator) thermal neutron detector. Its sensitivity ranges from thermal energies up to 1 GeV. A Monte Carlo characterization of this dual-detector rem counter has shown no significant change in the shape of the response curve obtained with the two detectors. The rem counter has been calibrated with a PueBe source. An intercomparison in a high-energy neutron field has been carried out at the CERF facility at CERN among the rem counter in the two configurations, two commercial units and the original version of the active LINUS in use at CERN. Both the active and passive versions of the rem counter agree, within the statistical ncertainties, with the CERN LINUS and with the facility reference values. Both versions of the instrument have proved to be capable of measuring the cosmic neutron background, thus providing a nonzero background measurement in environmental monitoring application