in-field use; compact neutron source; fast neutron generator; fast neutron imaging; industrial tomography
Soubelet B., Adams R., Kromer H., Zboray R., Prasser H.-M. (2019), Feasibility study of using a compact deuterium-deuterium (D-D) neutron generator for energy-selective transmission tomography, in Radiation Physics and Chemistry
, 156, 292-299.
Kromer Heiko, Adams Robert, Soubelet Benoit, Zboray Robert, Prasser Horst-Michael (2019), Thermal analysis, design, and testing of a rotating beam target for a compact D-D fast neutron generator, in Applied Radiation and Isotopes
, 145, 47-54.
Kromer H., Adams R., Soubelet B., Zboray R., Prasser H. M. (2018), Improvement of a Compact Fast Neutron Generator for Imaging Applications, in 2018 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)
, Sydney, Australia2018 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), Sydney, Australia.
Neutron imaging is becoming an increasingly popular non-destructive analysis (NDA) tool in research and it is also attracting growing interest from the industry for applications where NDA is offering clear advantages. Neutron imaging exhibits, in case of thermal or cold neutrons, very high sensitivity to specific light elements and considered to be complementary to gamma and X-rays that are sensitive for heavy elements. Fast neutrons (>1MeV) exhibit in general a lower elemental sensitivity; however, have high penetration power compared to the aforementioned radiation forms. This potentially enables the imaging of robust and bulky objects containing very significant amounts of both low-Z and high-Z materials which is challenging or even unfeasible with the other modalities.We have successfully developed in a precursor project a prototype small-sized, potentially portable fast neutron imaging system based on a compact, deuterium-deuterium (DD) neutron generator and a plastic scintillator detector arc. The system has been thoroughly tested in laboratory environment and the results are encouraging. Cross sectional tomographic imaging of specimen containing a combination of low-Z/ high-Z materials with diameters slightly above 10 cm is possible with a spatial resolution of around 2 mm. Exposure times of a few hours are needed to obtain reasonable image quality. In the frame of the project proposed here we plan to develop an upgrade of the prototype neutron generator. This will allow reducing the exposure time needed for the imaging and can enable the practical use of such device, on one hand, as a potential compact user facility for scientific research. The generator could be very valuable in applied scientific research where NDA of robust samples is needed (e.g. nuclear fuel bundle development). On the other hand, the in-field use of mobile NDA devices in real-life or industrial settings for applications that are not time critical, i.e. scanning times of tens of minutes up to an hour are allowed, would also be extremely useful. The two most promising applications for fast neutrons in this respect are: scanning of potentially hazardous individual objects (improvised explosives, explosive legacy, unexploded grenades etc.) and in-field industrial metrology. The latter is meant to test specimen from production lines for quality insurance purposes (investigate defects and confirm reliability, dimensions etc. of critical components). The most critical point to achieve the above goals is to maximize the neutron output of the compact neutron generator to levels enabling scanning of objects with exposure times in the order of minutes or tens of minutes. This should be achieved while keeping or possibly improving the aforementioned spatial resolution, aiming at 1 mm or in the slight sub-mm range. The size of objects that can be scanned with the device must be extended to its maximum (up to 20-25 cm diameter solid, plastic/heavy metal mixed objects should be possible). For this we will significantly increase the operating voltage (HV) of the generator by carefully optimizing the vacuum and HV design. To increase the neutron output, an optimized cooling and thermal design of the target in the generator is foreseen. Furthermore we will examine alternative target materials with improved inherent hydrogen storage and thermal properties that could potentially relax the requirements on cooling. This will involve challenging material science studies using advanced, microscopic analytical techniques to quantify different metal-hydrides target or potentially other deuterium-rich compounds. Finally, an efficient and optimized collimator arrangement must be developed, with the goal to minimize its volume and weight while retaining a sufficiently high suppression of secondary and scattered radiation. The scope of the work is a challenging, multidisciplinary topic for the promotion of a graduate in physics or engineering. The present application requests the funding of the position of a PhD student, together with the necessary financial means for supporting technical and engineering/scientific personnel given the significant technical and engineering design challenges extending over the scope of a common PhD work.