Simulation for neutron resonance absorption spectroscopic tomography

We are developing the pulsed neutron imaging technique using the time-of-flight (TOF) spectroscopy. Neutron resonance absorption spectroscopy (N-RAS) can identify individual nuclides, deduce its density and study its dynamics by analyzing energy, intensity and Doppler broadening of each resonance absorption peak. N-RAS/ computer tomography (CT), which is N-RAS combined with CT, can non-destructively show the tomographic image indicating the distribution of resonance nuclide and its dynamics inside various materials. However, large resonance absorption cross-section frequently causes the self-shielding effect, distorting the reconstructed CT image. Therefore, in the previous experiment, we obtained a reconstructed CT image different from the real distribution of resonance nuclide, using a data processing method without the self-shielding correction. For this reason, we have proposed a new data processing method to correct the self-shielding effect for N-RAS/CT, and carried out Monte-Carlo simulations to examine the feasibility of this method. As a result, we have succeeded in establishing a procedure that produces the undistorted CT image, indicating the absolute value of resonance nuclide density.