A novel detector for measuring gamma-ray fluxes in a mixed pulsed neutron-gamma radiation fields

An ICI (Insulator-Conductor-Insulator) gamma-ray detector designed for measurement of fast rising, high intensity pulsed gamma-ray fluxes has been developed. Like vacuum Compton diode (VCD) and dielectric Compton diode (DCD) devices, the ICI detector operates by utilization of the Compton effect. It has a very fast time response (rise time is less than 1 ns), a large linearity and a wide dynamic range. It is designed to measure intense and rapidly changing gamma-ray fluxes in highly mixed neutron-gamma radiation fields. Its sensitivity to 1.25 MeV gamma rays is about 1.8 × 10^-20 Coulombs · cm²/γ, for the 50 mm collimation diameter, which is relatively high compared with VCD and DCD devices. The simulated gamma-ray sensitivity agrees well with the experimental value. The gamma-to-neutron sensitivity ratio is about three orders of magnitudes for neutron energies below 14.1 MeV and 1.25 MeV gamma rays. Compared to existing VCD and DCD devices, the ICI detector requires no vacuum and power supply in operation, and also minimally attenuates a collimated gamma-ray beam due to its overall thickness of 3 mm in beam path.