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Journal Articles

Low-lying electric and magnetic dipole strengths in $$^{207}$$Pb

Shizuma, Toshiyuki*; Minato, Futoshi; Omer, M.*; Hayakawa, Takehito*; Ogaki, Hideaki*; Miyamoto, Shuji*

Physical Review C, 103(2), p.024309_1 - 024309_8, 2021/02

https://doi.org/10.1103/PhysRevC.103.024309
 Times Cited Count：0 Percentile：0.03(Physics, Nuclear)

Low-lying dipole transitions in $$^{207}$$Pb were measured via nuclear photon scattering using a quasi-monochromatic, linearly polarized photon beam. The electric ($$E1$$) and magnetic ($$M1$$) dipole strengths were extracted for excitation energies up to 6.8 MeV. The present ($$vec{gamma}$$,$$gamma'$$) results, combined with ($$gamma$$,$$n$$) data from the literature, were used to investigate the $$E1$$ and $$M1$$ photoabsorption cross sections near the neutron separation energy by comparison with predictions of the particle-vibration coupling on top of the quasi-particle random phase approximation (PVC+QRPA).

Journal Articles

Compton scattering of quasi-monochromatic $$gamma$$-ray beam

Omer, M.; Shizuma, Toshiyuki*; Hajima, Ryoichi*

Nuclear Instruments and Methods in Physics Research A, 951, p.162998_1 - 162998_6, 2020/01

https://doi.org/10.1016/j.nima.2019.162998
 Times Cited Count：0 Percentile：0.02(Instruments & Instrumentation)

Journal Articles

Validating polarization effects in $$gamma$$-rays elastic scattering by Monte Carlo simulation

Omer, M.; Hajima, Ryoichi*

New Journal of Physics (Internet), 21(11), p.113006_1 - 113006_10, 2019/11

AA2019-0407.pdf:0.73MB

https://doi.org/10.1088/1367-2630/ab4d8a
 Times Cited Count：4 Percentile：55.7(Physics, Multidisciplinary)

Journal Articles

Testing enrichment meter based on nuclear resonance fluorescence

Omer, M.; Shizuma, Toshiyuki*; Hajima, Ryoichi*; Koizumi, Mitsuo

Nihon Kaku Busshitsu Kanri Gakkai Dai-40-Kai Nenji Taikai Puroshidhingusushu, p.59 - 62, 2019/11

Journal Articles

Spin and parity determination of the 3.004-MeV level in $$^{27}$$Al; Its low-lying multiplet structure

Shizuma, Toshiyuki*; Omer, M.; Hajima, Ryoichi*; Shimizu, Noritaka*; Utsuno, Yutaka

Physical Review C, 100(1), p.014307_1 - 014307_6, 2019/07

https://doi.org/10.1103/PhysRevC.100.014307
 Times Cited Count：5 Percentile：69.53(Physics, Nuclear)

JAEA Reports

Geant4 physics process for elastic scattering of $$gamma$$-rays

Omer, 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 $$gamma$$-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 $$gamma$$-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 $$gamma$$-rays on NRF measurement. A new simulation code for the elastic scattering of $$gamma$$-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 $$gamma$$-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 $$gamma$$-rays. This research was implemented under the subsidiary for nuclear security promotion of MEXT.

Journal Articles

Including Delbr$"u$ck scattering in GEANT4

Omer, M.; Hajima, Ryoichi*

Nuclear Instruments and Methods in Physics Research B, 405, p.43 - 49, 2017/08

https://doi.org/10.1016/j.nimb.2017.05.028
 Times Cited Count：4 Percentile：50.55(Instruments & Instrumentation)

Elastic scattering of $$gamma$$-rays by an atom nearly associates all their interactions with matter. Therefore, the planning of experiments, involving measurements of $$gamma$$-rays, using Monte Carlo simulations usually includes the elastic scattering. However, current simulation tools do not provide a complete picture of the elastic scattering. The majority of these tools assume Rayleigh scattering is the primary contributor to the elastic scattering and neglect other elastic scattering processes, such as nuclear Thomson and Delbr$"u$ck scattering. Here, we develop a tabulation-based method to simulate elastic scattering in one of the most common open-source Monte Carlo simulation toolkits, GEANT4. We collectively include three processes, Rayleigh scattering, nuclear Thomson scattering, and Delbr$"u$ck scattering. Our simulation more appropriately uses differential cross sections based on the second-order scattering matrix instead of current data, which is based on the form factor approximation. Moreover, the superposition of these processes is carefully taken into account emphasizing the complex nature of the scattering amplitudes. The simulation covers an energy range of 0.01 MeV$$leq$$ E $$leq$$3 MeV and all elements with the atomic numbers of 1 $$leq$$ Z $$leq$$ 99. In addition, we verified our simulation by comparing the differential cross section measured in earlier experiments to those extracted from the simulations. We find that the simulations are in good agreement with the experimental measurements. Differences between the experiments and the simulations are 21% for uranium, 24% for lead, 3% for tantalum, and 8% for cerium at 2.754 MeV. Coulomb corrections to the Delbr$"u$ck amplitudes may account for the relatively large differences that appear at higher Z values.

Journal Articles

Effects of $$gamma$$-ray polarization in NRF-based nondestructive assay of nuclear materials

Omer, 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 $$gamma$$-ray beam, distinguishing the nature of the excitation is straightforward. At a scattering angle of 90$$^{circ}$$, 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 $$gamma$$-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 $$^{238}$$U using a 100% linearly polarized $$gamma$$-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.

Journal Articles

Simulation of the elastic scattering contributions to the NRF-based nondestructive assay of nuclear materials

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 $$gamma$$-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 $$gamma$$-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 $$^{238}$$U as a host material and less than 1% of $$^{239}$$Pu as an isotope of interest. When measuring NRF of $$^{239}$$Pu, there would be a huge background coming from the elastic scattering of $$^{238}$$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.

Journal Articles

Analysis of nuclear resonance fluorescence excitation measured with LaBr$$_{3}$$(Ce) detectors near 2 MeV

Omer, M.*; Negm, H.*; Ogaki, Hideaki*; Daito, Izuru*; Hayakawa, Takehito; Bakr, M.*; Zen, H.*; Hori, Toshitada*; Kii, Toshiteru*; Masuda, Kai*; et al.

Nuclear Instruments and Methods in Physics Research A, 729, p.102 - 107, 2013/11

https://doi.org/10.1016/j.nima.2013.06.083
 Times Cited Count：5 Percentile：43.78(Instruments & Instrumentation)

The performance of LaBr$$_{3}$$ (Ce) to measure nuclear resonance fluorescence (NRF) excitations is discussedin terms of limits of detection and in comparison with high-purity germanium (HPGe)detectors near the 2 MeV region where many NRF excitation levels from special nuclear materials are located. The NRF experiment was performed at the High Intensity Gamma-ray Source (HIGS) facility of Duke University. The incident $$gamma$$-rays, of 2.12 MeV energy, hit a B$$_{4}$$C target to excite the $$^{11}$$B nuclei to the first excitation level. The statistical-sensitive non-linear peak clipping (SNIP) algorithm was implemented to eliminate theback ground and enhance the limits of detection for the spectra measured with LaBr$$_{3}$$ (Ce). Both detection and determination limits were deduced from the experimental data.

Journal Articles

Nuclear resonance fluorescence of $$^{235}$$U measured with high-resolution LaBr$$_3$$(Ce) scintillation detectors

Omer, M.*; Negm, H.*; Zen, H.*; Daito, Izuru*; Kii, Toshiteru*; Masuda, Kai*; Ogaki, Hideaki*; Hajima, Ryoichi; Shizuma, Toshiyuki; Hayakawa, Takehito; et al.

Japanese Journal of Applied Physics, 52(10), p.106401_1 - 106401_4, 2013/10

https://doi.org/10.7567/JJAP.52.106401
 Times Cited Count：6 Percentile：30.5(Physics, Applied)

A nuclear resonance fluorescence (NRF) experiment was performed on a $$^{235}$$U target with quasi-monochromatic $$gamma$$-rays at the High Intensity Gamma-ray Source (HIGS) facility of Duke University using a 1733 keV resonant energy. A LaBr$$_3$$ (Ce) detector array consisting of eight cylindrical detectors, each with a length of 7.62 cm and a diameter of 3.81 cm, was implemented in this measurement. Moreover, a high-purity germanium (HPGe) detector array consisting of four detectors, each of which has a relative efficiency of 60%, was used as the benchmark for the measurement taken using the LaBr$$_3$$ (Ce) detector array. The integrated cross section of the NRF level, measured with LaBr$$_3$$ (Ce) detectors, showed good agreement with the available data.

Oral presentation

$$gamma$$-ray generation for detection of nuclear materials

Hayakawa, Takehito; Daito, Izuru; Kando, Masaki; Shizuma, Toshiyuki; Hajima, Ryoichi; Angell, C.; Ogaki, Hideaki*; Omer, M.*

no journal, , 

no abstracts in English

Oral presentation

Nuclear resonance fluorescence in U-238 using LaBr detectors for nuclear security

Hayakawa, Takehito; Negm, H.*; Ogaki, Hideaki*; Daito, Izuru*; Kii, Toshiteru*; Zen, H.*; Omer, M.*; Shizuma, Toshiyuki; Hajima, Ryoichi

no journal, , 

Recently, a nondestructive measurement method of shielded fissional isotopes such as $$^{235}$$U or $$^{239}$$Pu has been proposed for the nuclear security. These isotopes are measured by using nuclear resonance fluorescence (NRF) with monochromatic energy $$gamma$$-ray beams generated by laser Compton-scattering (LCS). We have proposed that one measure scattered $$gamma$$-rays from NRF with LCS $$gamma$$-ray beams using the LaBr$$_{3}$$(Ce) detectors. The LaBr$$_{3}$$(Ce) crystals include internal radioisotopes of a meta-stable isotope $$^{138}$$La and alpha decay chains from some actinides as $$^{227}$$Ac. There is a broad pump at about 2 MeV. This pump is considered to be an overlap of $$alpha$$-rays from decay chains of some actinides but its detailed structure has not been established. Here we have measured NRF spectra of $$^{238}$$U using the LCS $$gamma$$-rays with energy of about 2.5 MeV at the HIgS facility of the Duke University. The background has been evaluated using a simulation code GEAT4. The 9 peaks, 8 NRF $$gamma$$-rays plus the Compton scattered $$gamma$$-ray of the incident beam, are finally assigned in an energy range of about 200 keV at about 2.5 MeV. The 8 integrated NRF cross-sections measured by LaBr$$_{3}$$(Ce) have been consistent with results by an HPGe detector. The three levels are newly assigned using the HPGe detector. Two of them are also measured by LaBr$$_{3}$$(Ce).

Oral presentation

Nuclear resonance fluorescence measurement on Pb-207 with laser Compton scattering $$gamma$$ rays

Shizuma, Toshiyuki; Omer, M.; Hayakawa, Takehito; Ogaki, Hideaki*; Yamaguchi, Masashi*; Takemoto, Akinori*; Miyamoto, Shuji*

no journal, , 

no abstracts in English

Oral presentation

Extension of Geant4 toolkit for $$gamma$$-ray non-destructive assay of isotopes

Hajima, Ryoichi; Omer, M.

no journal, , 

Extension of Geant4 toolkit for $$gamma$$-ray non-destructive assay of isotopes is reported. In the extension, nuclear resonance fluorescence (NRF), a process to identify and assay isotope of interest, has been implemented. We have also implemented elastic scattering, background of NRF, as a sum of three different processes, Rayleigh scattering, nuclear Thomson scattering and Delbruck scattering. We present the result of the extension with simulation examples.

Oral presentation

Validating elastic scattering of polarized $$gamma$$-rays

Omer, M.; Shizuma, Toshiyuki*; Hajima, Ryoichi*; Angell, C.*

no journal, , 

An elastic scattering experiment has been performed using 100% linearly polarized $$gamma$$-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 $$gamma$$-rays is reported.

Oral presentation

Parities of low-energy states in Hf and W isotopes

Omer, M.; Shizuma, Toshiyuki*; Hajima, Ryoichi*; Koizumi, Mitsuo

no journal, , 

Nuclear resonance fluorescence experiments have been performed on Hf and W natural targets in the 2.5-3.1 MeV energy range using quasi monochromatic $$gamma$$-ray beams generated from laser Compton scattering at the HI$$gamma$$S facility, Duke University. The complete polarization of the incident $$gamma$$-rays has provided the determination of the parity of states in this energy range. Results of these experiment have revealed the parity of about 15 levels in Hf and W nuclei. Such data provide knowledge about the nondestructive detection system of nuclear material by understanding the so-called scissors mode encountered in deformed nuclei including uranium and plutonium isotopes.

Oral presentation

Improving Geant4 coherent scattering by adding nuclear Thomson and Delbr$"u$ck Processes

Omer, 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 $$gamma$$ rays. However, there are competing processes such as nuclear Thomson (NT) and Delbr$"u$ck (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.

Oral presentation

Nuclear resonance fluorescence measurement of Al-27 using polarized $$gamma$$-rays

Shizuma, Toshiyuki; Omer, M.; Hajima, Ryoichi; Koizumi, Mitsuo

no journal, , 

no abstracts in English

Oral presentation

Implementing elastic scattering of polarized MeV-photons in Geant4

Hajima, Ryoichi*; Omer, M.; Koizumi, Mitsuo

no journal, , 

Since elastic scattering of $$gamma$$ rays is a competitive process to nuclear resonance fluorescence, it represents a background in the non-destructive analysis of nuclear materials. Therefore, it is necessary to evaluate the influence of elastic scattering precisely. In Geant 4, widely used as a Monte Carlo code for radiation transport, we developed a code to calculate elastic scattering and published the paper in 2017. After that, we expanded the calculation code so that elastic scattering of polarized $$gamma$$ rays can be calculated, and is implemented in Geant 4. In this presentation, we report on calculation method of polarized $$gamma$$ ray elastic scattering in extended calculation code, outline the differential sectional area data used for calculation, and test with benchmark data obtained by experiment at Duke University. This research and development is a part of the project "subsidies for nuclear security enhancement promotion".

27 (Records 1-20 displayed on this page)