The compact energy resolved pixelated HEXITEC detector that uses CdTe (1mm thick) as the active detector material has been widely tested and characterised for its sensitivity to photon radiation but is yet to be tested under neutron radiation. In this project, the fast neutron and thermalised neutron sensitivity of the detector were tested by irradiation with 241AmBe radioisotope sources.
With the bare detector, the primary detection of the incoming neutron from the 241AmBe source is via prompt gamma emitted from the neutron inelastic scattering due to Cd in the detector element. Adding 0.5mm thick B4C and Gd2O3 on top of the detector to act as a conversion layer; producing prompt gammas from the neutron capture of B and Gd elements. In addition, the HEXITEC detector was also used tested for neutron source localization using the RadiCAL technique.
The result shows that the HEXITEC detector has the capability in detecting the neutron radiation through the prompt gamma detection of the CdTe detector when coupled with the Gd2O3 filter conversion layer. The result is validated with the combination of Pb and B4C shielding to cut off the gamma spectrum and thermal neutrons, respectively. The introduction of the Gd2O3 neutron conversion layer causes two low energy lines at ~50 and 55 keV to appear in the spectrum which are associated with prompt gamma emission from the Gd. The low energy features do not appear in the non-filter region. The result is also further validated with B4C filter, where the prompt gamma is outside the detector energy range. Higher energy Gd prompt gamma spectrum that within the detector range are yet to be found in the data. This is probably due to low efficiency from the 1 mm of CdTe detector material. Monte Carlo modelling will be required to investigate this further. However, the thin CdTe detector does not limited the detector capability in using the RadICAL technique. This preliminary study suggest that it is possible to further develop the CdTe detector for RadICAL applications in nuclear security where it is able to locate both gamma and neutron radiation.