Patent Number: 052951669
Section: abstract

A start-up range neutron monitor system for monitoring neutrons generated from a neutron source comprises a neutron detector disposed in a non-earthed state and adapted to detect neutrons generated from the neutron source, a coaxial cable for externally transmitting a detection signal from the neutron detector, the coaxial cable being composed of a core and an outer sheath, a preamplifier incorporated on a way of the coaxial cable for amplifiying the detection signal, and a signal processing unit connected to the preamplifier through the coaxial cable to process the amplified detection signal amplified. The coaxial cable is composed of a first cable portion connecting the neutron detector and the preamplifier on an input side thereof and a second cable portion connecting the preamplifier and the signal processing unit on an output side of the preamplifier. A cable shield is further disposed so as to cover the first cable portion of the coaxial cable, wherein an earth side circuit on the signal processing unit is earthed and the cable shield is connected to an earth side circuit of the preamplifier, thus constituting the entire system as one point earth structure. A coil assembly including including first and second coils are also incorporated in the core and outer sheath of the first cable portion of the coaxial cable respectively alone or together with the cable shield. The first and second coils have the same inductance and are arranged so as to generate magnetic fluxes in directions reverse to each other.