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storage phosphors to wide-range neutron detection坂佐井 馨; 藤 健太郎; 中村 龍也; 高倉 耕祐; 今野 力; 岩元 洋介
Proceedings of 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC), Vol.3, p.2024 - 2030, 2013/00
KCl:Eu輝尽性蛍光体を広領域の中性子検出に応用するため、本輝尽性蛍光体に
LiFとポリエチレンを混合したサンプルを製作し、FNSにて14MeV中性子照射実験を行った。その結果、ポリエチレン濃度が約5%で最大の輝尽性蛍光強度が得られることがわかった。これはモンテカルロ計算及び理論式によるエネルギー付与計算結果と一致した。また、低速・中速エネルギー範囲においては、Li(n,
)反応によるものが支配的であることもわかった。さらに、Li(n,)反応において、相対論を用いて粒子のエネルギーを中性子エネルギーの関数として計算したところ、中性子エネルギーが高い場合、実験室系では粒子は一定のエネルギーを有するのではなく、ある幅を持った一様分布になることがわかった。これを用いて粒子の平均の付与エネルギーを計算したところ、5MeV以上の中性子エネルギーではLi(n,)反応だけでなく、K(n,)反応のような核破砕反応がエネルギー付与に寄与することがわかった。
中村 龍也; 藤 健太郎; 川崎 卓郎; 本田 克徳; 鈴木 浩幸; 海老根 守澄; 美留町 厚; 坂佐井 馨; 曽山 和彦; 片桐 政樹*
Proceedings of 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC), Vol.4, p.2367 - 2369, 2013/00
硫化亜鉛蛍光体を用いた中性子検出器における検出効率の中性子入射角度依存性を評価した。中性子波長(1-8
)と入射角度をパラメータとし、J-PARCのパルス中性子を用いて実験的に評価した。試料としてZnS/LiFとZnS/
B
O
シンチレータを用いた。測定したそれぞれの試料(厚さは0.45と0.20mm)において中性子検出効率はいづれも3以下で入射角度の増加とともに増大することがわかった。発表では実験結果とモデル計算の比較結果について報告する。
大図 章; 中村 龍也; 高瀬 操; 倉田 典孝; 春山 満夫; 呉田 昌俊; 曽山 和彦; 瀬谷 道夫
Proceedings of 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 4 Pages, 2013/00
日本原子力研究開発機構では、保障措置用He-3中性子検出器の代替として固体シンチレータを用いた検出器を開発している。その検出器は、アルミニウム製の矩形チューブ(長さ約300mm, 32
32mm)、シンチレータシート(39mm250mm)、及び二つの光電子増倍管から構成される。シンチレータシートは、そのアルミニウム管内の矩形断面の斜め方向に設置され、光電子増倍管は管の両端に設置される。現在、検出効率としてHe-3検出器の約50%の値が得られ、かつ
線感度として510
が達成されている。この検出器の基本性能は、検出器管内のシンチレータ光の導光特性に大きく依存する。検出器管内のシンチレータ面から光電子増倍管までの光の伝送効率を光線追跡シミュレーションで評価した。その結果について、試験結果と比較して報告する。
山口 充孝; 長尾 悠人; 河地 有木; 藤巻 秀; 神谷 富裕; 小高 裕和*; 国分 紀秀*; 武田 伸一郎*; 渡辺 伸*; 高橋 忠幸*; et al.
Proceedings of 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 3 Pages, 2013/00
A Monte Carlo simulation system was developed to estimate the response of Compton camera against -ray emissions from RI spots in a PET-standard human-body phantom. The quality of the three-dimensional imaging program for the Si/CdTe Compton camera to reconstruct the image of the RI spots in a phantom was evaluated by the system, when the phantom has three hot sphere-regions with the same known RI density and different diameters, in other words, different known intensities. The density values of the hot regions reconstructed by the three-dimensional imaging program for the Compton camera were consistent to the known intensities of the RI. It demonstrates sufficient quality of the program for Si/CdTe Compton camera to image RI spots in the phantom.
山口 充孝; 鳥飼 幸太*; 河地 有木; 島田 博文*; 佐藤 隆博; 長尾 悠人; 藤巻 秀; 国分 紀秀*; 渡辺 伸*; 高橋 忠幸*; et al.
Proceedings of 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), 2 Pages, 2013/00
We studied a new method to monitor a beam range in heavy-ion radiation therapy on the basis of measurement of low energy photons emitted from a track of the ion beam. A 290 MeV/u carbon beam was injected into a cylindrical water phantom. A CdTe semiconductor detector with a lead slit having a width of 2 mm was placed at a side of the phantom. In order to measure the position dependence of the low energy photon count, the beam range was varied by changing the energy of injected ions using a binary energy degrader placed about 100 cm upstream of the beam focal point. The measured photon count decreased when the detector got closer to the end point of the beam range and the derivative of the photon count values sharply changed within a depth variation of a few mm in front of the range position. This was explained by our theoretical study assuming secondary electron bremsstrahlung. These results indicate that this new method could be useful to estimate the range position from the observation of bremsstrahlung with an accuracy of a few mm.
森下 祐樹; 山本 誠一*; 井崎 賢二; 金子 純一*; 東井 宏平*; 坪田 陽一*
no journal, ,
Monitoring of alpha-ray is used for detecting a nuclear fuel material (i.e. plutonium and uranium) in nuclear fuel facilities. Currently for monitoring of airborne contamination of nuclear fuel, only energy information measured by Si semiconductor detector is used to distinguish nuclear fuel material from radon daughters. In some cases, however, it is difficult to distinguish when the radon concentration is high (e.g. ventilation of rooms is poor). In addition Si semiconductor detector is generally sensitive to noise. In this study, we developed new alpha-ray imaging system by combining Si-PM array, which is insensitive to noise, with Ce-doped GdAlGaO
(GAGG:Ce) scintillator and evaluated basic performance of the developed system. Thickness of the scintillator was 0.1 mm and the light guide was 3.0 mm. An 
Am source was used for all measurement. The spatial resolution was evaluated by taking an image of a resolution chart.
長尾 悠人; 山口 充孝; 河地 有木; 藤巻 秀; 神谷 富裕; 武田 伸一郎*; 渡辺 伸*; 高橋 忠幸*; 鳥飼 幸太*; 荒川 和夫*; et al.
no journal, ,
We have been studying the application of Compton cameras to the field of medicine and biology. A quantitative image reconstruction method for Compton cameras has been investigated to analyze quantitatively the physiological functions of the target subjects, since it is essential to estimate the quantitative distribution of radioactive tracers within a given field of view (FOV) of the camera. Detection efficiency maps play an important role in quantitative image reconstruction in a statistical image reconstruction algorithm. Particularly, there are significant spatial variations of efficiency in the near-field area of the camera, which is the main FOV in the medical and biological application. A method to calculate the efficiency maps has been developed considering geometrical and physical conditions. A Monte Carlo simulation was carried out to test the validity of the method. The point sources of 511 keV photons were placed in a plane at a distance of 150 mm from the scattering detector of the CdTe Compton camera. The efficiency map agreed well with the result of Monte Carlo simulation. An imaging experiment of a 
Na source in the shape of line was performed using the efficiency map. The source was placed in the same plane as considered in Monte Carlo simulation. The shape of line is well reconstructed by list-mode ML-EM, though distribution of activity is not uniform sufficiently.
河地 有木; 尹 永根; 鈴井 伸郎; 石井 里美; 渡部 浩司*; 山本 誠一*; 藤巻 秀
no journal, ,
The uptake of radiocesium in plants from contaminated soil is a pressing issue, and a variety of agricultural research focusing on plant nutrition, including fertilizer management and plant breeding, has considered effective methods for both reducing uptake in crops and enhancing uptake in phytoremediation with plants. To investigate the uptake dynamics and behavior of radiocesium in plant, we employed a modified gamma camera previously used in biological and medical imaging experiments for imaging 662-keV photons from a Cs-137 source. The camera is composed of 22 22 gadolinium oxyorthosilicate (GSO) scintillators (15 mm thick) and a flat-panel position sensitive photomultiplier tube to obtain an adequately high sensitivity. A tungsten pinhole collimator was fabricated and mounted on the camera to prevent the penetration and scattering of the high-energy rays inside the collimator. Soybean plants, grown in hydroponic solutions and injected to approximately 2 MBq of Cs-137 were imaged after 21 h to investigate and visualize the uptake dynamics into the intact shoot system in real-time.
photon imaging河地 有木; 藤巻 秀; 渡部 浩司*; 山本 誠一*
no journal, ,
We have developed a gamma camera that employs a newly developed single-crystal scintillator, Ce-doped GdAlGaO (Ce:GAGG), which has no natural radioactivity, a relatively high density, and a large light output, as well as being nonhygroscopic. A 44 44 matrix of the Ce:GAGG pixels, 0.85 mm 0.85 mm 10 mm in size, was coupled to a high quantum efficiency position sensitive photomultiplier tube (HQE-PSPMT), and performance measurements indicate that almost all of the Ce:GAGG pixels were separated in the two-dimensional position histograms of 
Cs (662 keV) photons with an average peak-to-valley (P/V) ratio of 2. An energy resolution of 12.5
0.62% relative to the 662-keV photons was achieved. The camera was constructed by encasing the GAGG detector in a 20-mm-thick tungsten container with a pinhole collimator mounted on the front and setting the device on a positioning stand for both horizontal and vertical movement. Using the camera, we successfully imaged photons emitted from 
Cs (600 and 800 keV) and Cs (662 keV) solutions. Image data obtained at a distance of 300 mm from a Cs point source indicated that the position resolution was 13 mm, and the sensitivity obtained with a 1-mm-diameter collimator was 20 cpm/300 kBq.
山本 誠一*; 緒方 良至*; 河地 有木; 藤巻 秀
no journal, ,
Cerenkov light imaging of positron radionuclide has inherently high resolution and is promising for molecular imaging. Since the Cs and Cs emit beta particles, Cerenkov light imaging will be useful for the imaging of the radiocesium distribution. Consequently, we tested the Cerenkov light imaging for radiocesium solution to realize high resolution without contact to the subjects. We used high sensitivity cooled charge coupled device (CCD) camera (Hamamatsu Photonics, ORCA2-ER) for imaging the Cerenkov light. An f=0.95 lens (Xenon 0.95/25) was mounted with the camera and installed in a black box. Approximately 1cc solutions of Cs (
max energy: 0.66 MeV: 70%) and Cs (1.2 MeV: 5%, 0.5 MeV: 95%) (100 kBq each) were imaged with the CCD camera. With 2 min acquisition, the distribution of the Cs and Cs solutions started to be visualized and high resolution images could be obtained with 20-30 min acquisitions. With these results, we conclude that Cerenkov light imaging is promising for high resolution imaging the distribution of Cs and Cs.
