Response function measurement of layered type CVD single crystal diamond radiation detectors for 14 MeV neutrons

Abstract

Response function measurement of layered-type chemical vapor deposition single crystal diamond radiation detectors for $\text{14\hspace{0.5em}}\mathrm{MeV}$ neutrons was carried out. The detector had a layered structure that was composed of a boron-doped diamond layer of $\text{0.5\hspace{0.5em}μ}\mathrm{m}$ in thickness and a nondoped diamond layer of $\text{20\hspace{0.5em}μ}\mathrm{m}$ on an inexpensive high pressure and high temperature-type Ib diamond substrate. The detector had energy resolution of 2.6% for $\text{5.5\hspace{0.5em}}\mathrm{MeV}$ $\alpha$ particles. This experiment was mainly carried out in order to understand the present status of the detector as a $\text{14\hspace{0.5em}}\mathrm{MeV}$ neutron spectrometer and an extent of charge trapping. As result, a peak caused by the ${}^{12}\mathrm{C}{\mathrm{(n,\alpha }}_0{)}^9\mathrm{Be}$ reactions was clearly observed; the best energy resolution of 6% as for a synthetic diamond radiation detector was achieved. Detection efficiency was ${\text{3.2×10}}^{\text{−7}}$ counts/unit neutron fluence. However, taking the energy resolution for $\alpha$ particles, etc., into account, the energy resolution for $\text{14\hspace{0.5em}}\mathrm{MeV}$ neutrons was not so high. Further improvement based on better crystal growth is indispensable.