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-raysOmer, M.; Hajima, Ryoichi*
JAEA-Data/Code 2018-007, 32 Pages, 2018/06
JAEA-Data-Code-2018-007.pdf:2.64MB
JAEA-Data-Code-2018-007-appendix(CD-ROM).zip:22.71MB
Nuclear resonance fluorescence (NRF) is a promising technique for the non-destructive assay (NDA) of nuclear materials. Its powerfulness is apparent in the highly penetrative -rays emitted in an isotopic fingerprint of the NRF interactions. However; there exist other interactions that may interfere with the NRF and hence, may limit its accuracy. Of these interactions is the elastic scattering of -rays by atoms which needs further investigation and testing. Japan Atomic Energy Agency started in 2015 to develop a NDA system based on the NRF for nuclear non-proliferation and nuclear security purposes. One of the tasks of the current development is assessing the effect of the elastic scattering of -rays on NRF measurement. A new simulation code for the elastic scattering of -rays has recently been developed in the Geant4 environment. The present JAEA-Data/Code report provides a more detailed description of the simulation code as well as an elaborated illustration of the elastic scattering of -rays and its interaction cross sections. This report facilitates user feedback of the simulation code which is indispensable for reaching a stable and reliable simulation. The current report would contribute to better understanding of the elastic scattering of -rays. This research was implemented under the subsidiary for nuclear security promotion of MEXT.
-ray polarization in NRF-based nondestructive assay of nuclear materialsOmer, M.; Hajima, Ryoichi*; Shizuma, Toshiyuki*; Koizumi, Mitsuo
Proceedings of INMM 58th Annual Meeting (Internet), 7 Pages, 2017/07
Nuclear resonance fluorescence (NRF) is a process in which the electric and/or the magnetic dipole excitations of the nucleus take place. Since these excitations are unique signatures of each nucleus, the NRF provides a practical tool for a non-destructive detection and assay of nuclear materials. Using a polarized -ray beam, distinguishing the nature of the excitation is straightforward. At a scattering angle of 90
, the electric dipole excitations are radiated normal to the polarization plane whereas the magnetic dipole excitations are radiated in the same plane as the incident beam polarization. By contrast, other -ray interactions with the atom may exhibit different responses regarding the polarization of the incident beam. For example, the elastic scattering is expected to give approximately 60% lower yield in the direction of the incident beam polarization than the other direction. This fact significantly affects the sensitivity of the NRF technique because it is not possible to separate the NRF and the elastic scattering on the basis of the photon energy. We report the results of a photon scattering experiment on 
U using a 100% linearly polarized -ray beam with an energy of 2.04 MeV. We demonstrate how the elastic scattering responds to the polarization of the incident beam. Accordingly, we are able to resolve the effects of the polarization of incident photon in an NRF measurement.
Omer, M.; Hajima, Ryoichi*; Angell, C.*; Shizuma, Toshiyuki*; Hayakawa, Takehito*; Seya, Michio; Koizumi, Mitsuo
Proceedings of INMM 57th Annual Meeting (Internet), 9 Pages, 2016/07
Isotope-specific -rays emitted in the nuclear resonance fluorescence (NRF) process provide a good technique for a non-destructive detection and assay of nuclear materials. We are developing technologies relevant to -ray nondestructive detection and assay utilizing NRF. A Monte Carlo code to simulate NRF process is necessary for design and evaluation of NDA systems. We are developing NRFGeant4, a Geant4-based simulation code, for this purpose. In NRF experiments, highly-enriched targets are generally used such that the NRF signals are dominant and easily measured. In contrast, a real situation may involve very small contents of isotopes of interest. This results in a difficulty in measuring NRF signals because of the interference with other interactions, e.g. elastic scattering. For example, a typical nuclear fuel pellet contains about 90% of U as a host material and less than 1% of 
Pu as an isotope of interest. When measuring NRF of Pu, there would be a huge background coming from the elastic scattering of U. Therefore, an estimation of the elastic scattering with the host material is essential for precise determination of isotope of interest. Satisfying estimation of elastic scattering is currently not available except for some calculations. In the present study, we upgrade our simulation code to include the calculation of elastic scattering events.
-raysOmer, M.; Shizuma, Toshiyuki*; Hajima, Ryoichi*; Angell, C.*
no journal, ,
An elastic scattering experiment has been performed using 100% linearly polarized -rays generated by laser Compton backscattering at Duke University, NC, USA. Photons of energy of 2 MeV elastically scattered off uranium target were measured with high-purity Ge detectors. The results are used in the simulation study to improve the sensitivity of identifying isotopes by nuclear resonance fluorescence. Validation of the elastic scattering cross section of a polarized -rays is reported.
ck ProcessesOmer, M.; Hajima, Ryoichi*
no journal, ,
This paper proposes an improvement to the Geant4 coherent scattering by implementing additional physics processes that are not currently taken into account. Coherent or elastic scattering is treated in Geant4 in a way such that only Rayleigh process (R) is the unique contributor to the entire elastic scattering of rays. However, there are competing processes such as nuclear Thomson (NT) and Delbrck (D) processes which are treated for the first time in the present work. A significant aspect encountered at implementing elastic scattering simulation is the interference among the different scattering amplitudes of R, NT, and D. Therefore; we prepared the required amplitudes of R based on the scattering matrix calculations, amplitudes of D based on the lowest order Born approximation, and amplitudes of NT based on an analytical equation. This present simulation is essential in implementing a star-to-end simulation of a nondestructive assay of nuclear materials using nuclear resonance fluorescence.