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論文

Calculating off-axis efficiency of coaxial HPGe detectors by Monte Carlo simulation

Omer, M.; 静間 俊行*; 羽島 良一*; 小泉 光生

Radiation Physics and Chemistry, 198, p.110241_1 - 110241_7, 2022/09

https://doi.org/10.1016/j.radphyschem.2022.110241
 被引用回数：2 パーセンタイル：53.91(Chemistry, Physical)

In beam geometries where a directed $$gamma$$-ray beam hits the surface of a coaxial high purity germanium detector (HPGe), the detector efficiency is sensitive to the position where $$gamma$$-rays initially hit the detector surface because the structure of the detector is nonuniform. This may cause inaccuracy of the detector efficiency when measured using standard sources that are point-like sources emitting $$gamma$$-rays isotropically. Obtaining a precise estimation of the full energy peak efficiency of the coaxial HPGe detector in the beam geometry for on-axis and off-axis measurements requires a Monte Carlo simulation. We performed a Monte Carlo simulation that calculates the detector efficiency in the beam geometry. The effects of the off-axis distance and $$gamma$$-ray beam size on the efficiency are quantitatively analyzed. We found that the intrinsic efficiency in the beam geometry is maximized when the beam hits the detector at specific off-axis distances. Our Monte Carlo calculations have been supported by a nuclear resonance fluorescence experiment using laser Compton scattering $$gamma$$-ray beam.

論文

Determination of detection efficiency curves of HPGe detectors on radioactivity measurement of volume samples

三枝 純; 川崎 克也; 三原 明; 伊藤 光雄; 吉田 真

Applied Radiation and Isotopes, 61(6), p.1383 - 1390, 2004/12

https://doi.org/10.1016/j.apradiso.2004.04.004
 被引用回数：28 パーセンタイル：84.49(Chemistry, Inorganic & Nuclear)

$$gamma$$線スペクトロメトリ法により体積試料の放射能測定を行う際、各試料に固有の効率曲線が必要となる。環境試料の放射能測定や緊急時の試料測定においては、100keV以下の低エネルギー$$gamma$$線を放出する核種の評価が重要となる。ここでは、代表点法を用いて体積試料に対するHPGe検出器の効率を評価するとともに、低エネルギー$$gamma$$線に対する効率曲線を評価するうえで重要な補正因子となる自己吸収効果について詳細に検討した。また、代表点法を種々環境試料の測定に適用し実務へ活用するうえでの基礎データとした。

論文

Beta-decay energies of $$^{121,123,125}$$Ba and $$^{121-124,126}$$Cs

長 明彦; 生田 智彦*; 河出 清*; 山本 洋*; 市川 進一

Journal of the Physical Society of Japan, 65(4), p.928 - 934, 1996/04

https://doi.org/10.1143/JPSJ.65.928
 被引用回数：16 パーセンタイル：71.32(Physics, Multidisciplinary)

中性子欠損核の$$^{121,123,125}$$Baと$$^{121-124,126}$$Cs同位体の$$beta$$+線最大エネルギーを高純度ゲルマニウム(HPGe)検出器を用いて測定した。線源は20MVタンデム静電加速器で加速した$$^{32}$$S$$^{10+}$$,$$^{35}$$Cl$$^{11+}$$のイオンビームをMoターゲットに照射し、核反応生成物をオンライン同位体分離器で質量分離することで得た。$$beta$$線スペクトルの解析にはHPGe検出器の単一エネルギー陽電子線に対する応答関数を用い、$$beta$$$$^{+}$$線最大エネルギー及び軌道電子捕獲崩壊のQ値(Q$$_{EC}$$値)を求めた。$$^{121,123}$$BaのQ$$_{EC}$$値を初めて実験的に求めると共に、他の同位体のQ$$_{EC}$$値についても精度を向上した。

口頭

LCSガンマ線源を使用したビーム形状における同軸HPGe検出器の効率の評価

Omer, M.; 静間 俊行*; 羽島 良一*; 小泉 光生; 平 義隆*

no journal, , 

High-resolution $$gamma$$-ray spectroscopy involving beam geometry may be measured with higher efficiency if $$gamma$$-ray beam hits out of the axis of the coaxial HPGe detector. Hitting off-axis makes $$gamma$$-rays avoid travelling through the contact hole, which is an inactive axial portion of the detector. We performed Monte Carlo simulations to study the effects of contact hole dimensions and off-axis distance on the coaxial HPGe detector efficiency. The simulation considered $$gamma$$-ray energy up to 10 MeV. In general, the simulation results reveal that the off-axis efficiency is higher than on-axis efficiency for a wide range of $$gamma$$-ray energies and beams sizes. Our simulations results are validated by experimental measurements of $$gamma$$-ray beams generated from laser Compton scattering at UVSOR III facility.

口頭

Investigating effects of coaxial HPGe detector structure on the measurement of LCS $$gamma$$-ray beam

Omer, M.; 静間 俊行*; 小泉 光生; 羽島 良一*; Zen, H.*; 平 義隆*

no journal, , 

Coaxial high-purity germanium detectors are essential components of high-resolution $$gamma$$-ray spectrometers. Indeed, these detectors come in various dimensions with different internal structures. Particularly when the measured $$gamma$$-rays are in the form of a directed beam, the detector internal structure may affect the measured $$gamma$$-ray spectra significantly. Here we investigate the effect of the internal structure of two different coaxial HPGe detectors using 5.54 MeV $$gamma$$-rays generated by laser Compton scattering at the UVSOR III facility. The $$gamma$$-ray beam hit the detectors in two configurations, axial and nonaxial. We found that the nonaxial configuration provides higher efficiency and lower background than the axial configuration, which was confirmed using Monte Carlo simulations. Our results provide improvements in the measurement of $$gamma$$-ray beams. This work is a contribution of the Japan Atomic Energy Agency (JAEA) to the International Atomic Energy Agency (IAEA) under the agreement of the coordinated research program (CRP), J02015 (Facilitation of Safe and Secure Trade Using Nuclear Detection Technology - Detection of RN and Other Contraband).

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