Design of a Photoneutron Convertor for Energy Selective Neutron Imaging

Neutron imaging plays an essential role in the industrial applications, such as turbine blade manufacturing, fuel cell research, and nuclear fuel quality inspection. As isotopic neutron sources and neutron generators cannot provide high-intensity neutron beams, and neutron beam lines of research reactors or spallation neutron sources are very scarce, a cost-effective neutron source with high neutron yield and long lifespan should be researched. The e-LINAC driven photoneutron source, which converts X-rays to photoneutrons, has been proved to be a robust neutron source that can realize neutron yield ranging from 1010to 1015n/s. Hence it is a promising neutron source to provide neutron beams used for the neutron imaging. Because the e-LINAC works at a pulsed mode and the photoneutrons have a continuous energy spectrum, energy selective neutron imaging can thus be realized with the e-LINAC driven photoneutron source, with the aid of time of flight (TOF) technique. In this research, an e-LINAC driven photoneutron source is researched to strike the compromise between the neutron flux and the energy resolution. With a well-designed heavy water photon-to-neutron convertor, a 10 MeV/ 20 kW eLINAC can provide a thermal neutron flux of 7.28 × 104n/cm2/s at 10 meters away from the electron target, with an energy resolution less than 20%. By using a low temperature (10K) moderator, the cold neutron flux at the same position can be 2.13 × 104n/cm2, and the energy resolution is less than 2%. This study may help realize the energy selective neutron imaging with an e-LINAC driven photoneutron source.