In neutron transmutation doped germanium, the thermal neutron fluence of reactor irradiation is as high as 10$^{ 18}$~n$\cdot$cm$^{ -2}$. For radiological safety reasons, general Co or Au neutron flux monitors cannot be easily used. We have experimentally demonstrated the feasibility of measuring the X-rays emitted by the NTD-Ge itself to determine the absolute thermal neutron fluence for the first time. A Micro-Megas Detector (MMD) and a Silicon Drift Detector (SDD) are set up to detect the tagging KX-rays with 9.2 keV and 10.3 keV cascading from the decays of $^{ 71}$Ge. Combined the detection efficiencies calculated by GEANT4, neutron fluence results given with proper accuracy by MMD and SDD are in a good agreement with each other.
Categories: physics.ins-det hep-ex nucl-ex