Synthetic single crystal diamond as a fission reactor neutron flux monitor

Thermal neutron flux monitors were fabricated using chemical vapor deposited single crystal diamond in a p-type/intrinsic/metal/6LiF layered structure. They were placed 80 cm above the core midplane of a 1 MW research fission reactor, where the maximum neutron flux is 2.2×109 neutrons/cm2 s. Good stability and reproducibility of the device response were observed over the whole reactor power range. A 150 000 counts/s count rate was measured at the maximum reactor power with no degradation of the detector signal. As the multiple pile-up process due to the slow readout electronics is accounted for, an excellent linearity of the diamond response is observe