Response of a diamond detector sandwich to 14 MeV neutrons

Abstract

In this paper we present the measurement of the response of 50μm thin diamond detectors to 14MeV neutrons. Such neutrons are produced in fusion reactors and are of particular interest for ITER neutron diagnostics. Among semiconductor detectors diamond has properties most appropriate for harsh radiation and temperature conditions of a fusion reactor. However, 300–500μm thick diamond detectors suffer significant radiation damage already at neutron fluences of the order of 1014n/cm2. It is expected that a 50μm thick diamond will withstand a fluence of >1016n/cm2. We tested two 50μm thick single crystal CVD diamonds, stacked to form a “sandwich” detector for coincidence measurements. The coincidence between two diamonds allows to suppress background and increase detection efficiency. The detector measured the conversion of 14MeV neutrons, impinging on one diamond, into α particles which were detected in the second diamond in coincidence with nuclear recoil. For C12(n,α)Be9 reaction the total energy deposited in the detector gives access to the initial neutron energy value. The measured 14MeV neutron detection sensitivity through this reaction by a detector of an effective area 3×3mm2 was 5×10−7 counts cm2/n. This value is in good agreement with Geant4 simulations. The energy resolution of the detector was found to be 870keV FWHM, but according to Geant4 simulations only about 160keV FWHM were intrinsic.