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Rodriguez, D.; Bogucarska, T.*; 小泉 光生; Lee, H.-J.; Pedersen, B.*; Rossi, F.; 高橋 時音; Varasano, G.*
Nuclear Instruments and Methods in Physics Research A, 997, p.165146_1 - 165146_13, 2021/05
被引用回数：2 パーセンタイル：18.91(Instruments & Instrumentation)Under the MEXT subsidy to strengthen nuclear security related research, the ISCN is developing delayed gamma-ray spectroscopy (DGS) for nuclear safeguards. Here we present results from experiments using the PUNITA instrument in collaboration with JRC-Ispra to evaluate the gamma-ray spectral dependence on interrogation time patterns and number of cycles. Specifically, we investigated the observable gamma rays useful to quantify the 
Pu and 
U contributions. Of the time patterns tested in this study, we determined that irradiating the sample for 60-
followed by a gamma-ray measurement of 60- was the best for a comparable one-hour total interrogation time.
Rossi, F.; 小泉 光生; Lee, H.-J.; Rodriguez, D.; 高橋 時音; Abbas, K.*; Bogucarska, T.*; Crochemore, J.-M.*; Pedersen, B.*; Varasano, G.*
61st Annual Meeting of the Institute of Nuclear Materials Management (INMM 2020), Vol.2, p.907 - 911, 2021/00
Delayed Gamma-ray Spectroscopy (DGS) is a nondestructive assay technique with the capability to quantify the fissile composition of small nuclear material samples from reprocessing plants. In recent years, the Japan Atomic Energy Agency in collaboration with the Joint Research Centre performed several experiments using uranium and plutonium standard samples. In this paper, we present some of our recent experiment results showing the feasibility of DGS for fissile mass estimation. In particular, we interrogate uranium samples of different enrichment and we are showing that we were able to qualify significant peaks even for a depleted uranium sample above 2.7 MeV. Applying correction factors for neutron self-shielding and gamma self-absorption, we obtained a mass linear correlation when considering total integrated counts above 3.3 MeV as well as specific individual peak counts. This work is supported by the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT) under the subsidy for the "promotion for strengthening nuclear security and the like". This work was done under the agreement between JAEA and EURATOM in the field of nuclear material safeguards research and development.
Rossi, F.; Bogucarska, T.*; 小泉 光生; Lee, H.-J.; Pedersen, B.*; Rodriguez, D.; 高橋 時音; Varasano, G.*
Nuclear Instruments and Methods in Physics Research A, 977, p.164306_1 - 164306_7, 2020/10
被引用回数：4 パーセンタイル：36.4(Instruments & Instrumentation)The Japan Atomic Energy Agency and the European Commission Joint Research Centre are collaborating to develop delayed gamma-ray spectroscopy (DGS) for nuclear materials for safeguards verification in reprocessing plants. In this paper, we describe DGS interrogation using the Pulsed Neutron Interrogation Test Assembly with standard samples of different U enrichments. By analyzing gamma-ray spectra, we reveal a linear correlation between the sample mass and both the total counts above 3.3 MeV and the peak counts of specific high-energy gamma-ray. We were able to observe, qualify and quantify specific gamma rays peak down to the depleted uranium (0.5 gU) mass sample. Based on this, we demonstrate that our technique is able to estimate the total fissile mass with a statistical uncertainty 
2% when taking into account self-shielding and gamma self-absorption corrections. Using integrated counts above 3.3 MeV we were able to reduce the mass-dependent bias for the higher enrichments (
3 to 4%) to 4%. This work is supported by the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT) under the subsidiary for the "promotion for strengthening nuclear security and the like". This work was done under the agreement between JAEA and EURATOM in the field of nuclear materials safeguards research and development.
-Irradiated n-type 4H-SiCBeyer, F. C.*; Hemmingsson, C. G.*; Pedersen, H.*; Henry, A.*; 磯谷 順一*; 森下 憲雄*; 大島 武; Janz
n, E.*
Journal of Physics D; Applied Physics, 45(45), p.455301_1 - 455301_7, 2012/11
被引用回数：18 パーセンタイル：57.55(Physics, Applied)A bistable center, named FB center, in electron irradiated 4H-SiC was observed using capacitance transient techniques. In configuration called "
", the deep level known as EH5 (
= 
- 1.07 eV) is detected in the deep level transient spectroscopy spectrum, whereas for configuration called "
", no obvious deep level is observed in the accessible part of the band gap. Isochronal annealing revealed that the transition temperatures to be from to is more than 730K, and for the opposite process from to is about 710 K. The energy needed to conduct the transformations were determined to be 
( to ) = (2.1 
0.1) eV and ( to ) = (2.3 0.1) eV, respectively. Since the bistable FB centre is already present after low-energy electron irradiation (200 keV), it is likely related to carbon.
-type 4H-SiCBeyer, F. C.*; Hemmingsson, C.*; Pedersen, H.*; Henry, A.*; Janzn, E.*; 磯谷 順一*; 森下 憲雄*; 大島 武
Journal of Applied Physics, 109(10), p.103703_1 - 103703_6, 2011/05
被引用回数：17 パーセンタイル：57.65(Physics, Applied)耐放射線性半導体として期待される炭化ケイ素(SiC)の照射欠陥に関する知見を得るため、型六方晶(4H)SiCへ200keVの電子線を5
10
/cm
照射した。DLTS(Deep Level Transient Spectroscopy)測定の結果、Mセンターと呼ばれる欠陥が観測された。試料を熱処理することでMセンターの振舞いを調べたところ、Mセンターが消滅する過程で、新たにEBセンターと呼ばれる欠陥が発生することが判明した。EBセンターの増加の振る舞いがMセンターの減少と一致することから、EBセンターはMセンターが熱処理により構造を変化させて新たな欠陥構造になったと結論できた。さらに熱処理温度を上昇させると、700
CでEBセンターも消滅することも判明した。使用した電子線のエネルギーがSiC中のシリコン(Si)のはじき出しのしきい値エネルギー以下であることから、今回観察されたMセンター,EBセンターともに炭素(C)が関連する欠陥中心であることが示唆された。
Beyer, F. C.*; Hemmingsson, C.*; Pedersen, H.*; Henry, A.*; 磯谷 順一*; 森下 憲雄; 大島 武; Janzn, E.*
Materials Science Forum, 645-648, p.435 - 438, 2010/00
炭化ケイ素(SiC)半導体へ電子線を照射することで発生する欠陥に関して、DLTS(Deep Level Transient Spectroscopy)を用いて調べた。n型六方晶(4H)SiCに200keV電子線を照射したところ、Z1/2, EH6/7, EH1及びEH3と呼ばれる欠陥が観測された。さらに、照射した試料へ650Kまでの熱処理をしたところ、EH1及びEH3が消失すると同時に、新たに、EBセンターと名付けられた欠陥群が発生することが観察された。200keV電子線がSiC中の炭素のみをはじき出すことを考慮すると、今回観察された欠陥は、すべて炭素起因であると言える。
Rossi, F.; Abbas, K.*; 小泉 光生; Lee, H.-J.; Nonneman, S.*; Pedersen, B.*; Rodriguez, D.; 高橋 時音
no journal, ,
In the field of nuclear material samples safeguard verifications, mixed high-radioactivity nuclear material in facility like reprocessing nuclear plant are challenging. Addressing this, the JAEA/ISCN is developing a DG-nondestructive assay technique. We successfully completed several experiments in collaboration with the EC/JRC to evaluate the instrumentation requirements of a compact instrument. In principle, a neutron source is used to produce neutrons that are then thermalized in a moderator before reaching the sample to induce fission. The optimization of the moderator is crucial to reach an efficient and compact instrument. Having a good thermalized neutron flux enhances the delayed gamma-ray signature of the fissile due to their greater thermal fission cross section compared to the fertile. After the irradiation, the gamma-ray peaks above 3 MeV are analyzed to determine the initial composition of the fissile nuclides. The gamma-ray spectrum and subsequent analysis are strongly affected by the source type; the sample; and the interrogation pattern, driven by the analysis. To investigate all these aspects, we performed several experiments using small standard samples of both Uranium and Plutonium with PUNITA to understand basic principles. These were factored into the JAEA DGCT instrument that was tested in PERLA. This work first describes the PUNITA and PERLA experiments and how these were used to validate the various model designs. From these, further modifications to reach our final instrument concept design for a deuterium-deuterium neutron generator source are presented. This work is supported by MEXT under the subsidy for the "promotion for strengthening nuclear security and the like". This work was done under the agreement between JAEA and EURATOM in the field of nuclear material safeguards research and development.
