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A Correction method based on probability density function and measurement volume for turbulence intensity profile measured by LDV in turbulent pipe flow

和田 裕貴; 古市 紀之*; 草野 英祐*; 辻 義之*

Proceedings of 15th International Conference on Flow Dynamics (ICFD 2018) (USB Flash Drive), p.778 - 779, 2018/11



Further experiments for mean velocity profile of pipe flow at high Reynolds number

古市 紀之*; 寺尾 吉哉*; 和田 裕貴; 辻 義之*

Physics of Fluids, 30(5), p.055101_1 - 055101_7, 2018/05


This paper reports further experimental results obtained in high Reynolds number actual flow facility in Japan. The experiments were performed in a pipe flow with water, and the friction Reynolds number was varied up to $$Re_{tau}$$ = 5.3 $$times$$ 10$$^{4}$$. This high Reynolds number was achieved by using water as the working fluid and adopting a large-diameter pipe (387 mm) while controlling the flow rate and temperature with high accuracy and precision. The streamwise velocity was measured by laser Doppler velocimetry close to the wall, and the mean velocity profile, called log-law profile $$U^{+}$$ = (1/$$kappa$$) ln(y$$^{+}$$) + $$B$$, is especially focused. After careful verification of the mean velocity profiles in terms of the flow rate accuracy and an evaluation of the consistency of the present results with those from previously measurements in a smaller pipe (100 mm), it was found that the value of $$kappa$$ asymptotically approaches a constant value of $$kappa$$ = 0.384.


Imaging of radiocesium dynamics in soybean by using a high-resolution gamma camera

尹 永根; 河地 有木; 鈴井 伸郎; 石井 里美; 吉原 利一*; 渡部 浩司*; 山本 誠一*; 藤巻 秀

JAEA-Review 2015-022, JAEA Takasaki Annual Report 2014, P. 112, 2016/02

Large areas of agricultural fields were contaminated with radiocesium ($$^{134}$$Cs and $$^{137}$$Cs) in Japan by the accident of The Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station in March 2011. Many agricultural studies, such as fertilizer management and plant breeding, are undertaken for reducing radiocesium uptake in crops or enhancing of uptake and transportation via phytoremediation. These studies examine the control of radiocesium transport into/within plant bodies from the viewpoint of plant physiology. Radiotracer imaging is one of the few methods that enable the observation of the movement of substances in a living plant, like a video camera, without sampling of the plant tissues. In this study, we performed the imaging of $$^{137}$$Cs uptake and transport from root to aerial part by using a new gamma camera in intact soybean plants because contamination of soybean by radiocesium has currently become a major problem in agriculture in Fukushima.


Development of a gamma camera system for high-energy gamma photon for quantitative observation of $$^{137}$$Cs movement in a plant body

河地 有木; 尹 永根; 鈴井 伸郎; 石井 里美; 吉原 利一*; 渡部 浩司*; 山本 誠一*; 藤巻 秀

JAEA-Review 2015-022, JAEA Takasaki Annual Report 2014, P. 94, 2016/02

We developed an original gamma camera system to image radiocesium in a plant. The gamma camera was designed for high-energy gamma photons from $$^{137}$$Cs radiocesium (662 keV). We performed tests to evaluate the position resolution and quantitative linearity of the gamma camera. The best spatial resolution of this gamma camera was determined to be 19.1 mm in full width at half maximum at the center of the field-of-view. And a result shows a quantitative linearity of the image data with a correlation of ${it r$^{2}$}$ = 0.9985 between the source activity and the count rate. We conclude the gamma camera system has sufficiently high capability to obtain quantitative and dynamic images of $$^{137}$$Cs movement in intact plants.


Imaging of radiocesium uptake dynamics in a plant body by using a newly developed high-resolution gamma camera

河地 有木; 尹 永根; 鈴井 伸郎; 石井 里美; 吉原 利一*; 渡部 浩司*; 山本 誠一*; 藤巻 秀

Journal of Environmental Radioactivity, 151(Part 2), p.461 - 467, 2016/01

 被引用回数:5 パーセンタイル:53.85(Environmental Sciences)

We developed a new gamma camera specifically for plant nutritional research and successfully performed live imaging of the uptake and partitioning of $$^{137}$$Cs in intact plants. The gamma camera was specially designed for high-energy $$gamma$$ photons from $$^{137}$$Cs (662 keV). To obtain reliable images, a pinhole collimator made of tungsten heavy alloy was used to reduce penetration and scattering of $$gamma$$ photons. The array block of the GAGG scintillator was coupled to a high-quantum efficiency position sensitive photomultiplier tube to obtain accurate images. The completed gamma camera had a sensitivity of 0.83 count s$$^{-1}$$ MBq$$^{-1}$$ for $$^{137}$$Cs, and a spatial resolution of 23.5 mm. We used this gamma camera to study soybean plants that were hydroponically grown and fed with 2.0 MBq of $$^{137}$$Cs for 6 days to visualize and investigate the transport dynamics in aerial plant parts. $$^{137}$$Cs gradually appeared in the shoot several hours after feeding, and then accumulated preferentially and intensively in growing pods and seeds; very little accumulation was observed in mature leaves. Our results also suggested that this gamma-camera method may serve as a practical analyzing tool for breeding crops and improving cultivation techniques resulting in low accumulation of radiocesium into the consumable parts of plants.


Simulation study of power load with impurity seeding in advanced divertor "short super-X divertor" for a tokamak reactor

朝倉 伸幸; 星野 一生; 清水 勝宏; 新谷 吉郎*; 宇藤 裕康; 徳永 晋介; 飛田 健次; 大野 哲靖*

Journal of Nuclear Materials, 463, p.1238 - 1242, 2015/08

 被引用回数:8 パーセンタイル:18.09(Materials Science, Multidisciplinary)



Analysis of tungsten transport in JT-60U plasmas

清水 友介*; 藤田 隆明*; 有本 英樹*; 仲野 友英; 星野 一生; 林 伸彦

Plasma and Fusion Research (Internet), 10(Sp.2), p.3403062_1 - 3403062_4, 2015/07

In JT-60U, it has been observed that accumulation of tungsten is enhanced with increasing the toroidal rotation in the opposite direction (CTR-rotation) to the plasma current in H-mode plasmas. Two models for convective transport, pinch due to the toroidal rotation (PHZ pinch) and the radial electric field (Er pinch) were proposed. We introduce these two pinch models into integrated transport code TOTAL, and study dependence of the tungsten accumulation on the toroidal rotation. In the high toroidal rotation velocity, we obtained the tungsten accumulation four times as large as in the low one. The model reproduces the trend observed in the experiment.



藤巻 秀

放射線と産業, (138), p.25 - 28, 2015/06



Monitoring of positron using high-energy gamma camera for proton therapy

山本 誠一*; 歳藤 利行*; 小森 雅孝*; 森下 祐樹*; 奥村 聡*; 山口 充孝; 齋藤 勇一; 河地 有木; 藤巻 秀

Annals of Nuclear Medicine, 29(3), p.268 - 275, 2015/04

 被引用回数:6 パーセンタイル:48.07(Radiology, Nuclear Medicine & Medical Imaging)

In proton therapy, imaging of proton-induced positrons is a useful method to monitor the proton beam distribution after therapy. We developed a small field-of-view gamma camera for high-energy gamma photons and used it for monitoring the proton-induced positron distribution. The gamma camera used 0.85 mm $$times$$ 0.85 mm $$times$$ 10 mm GAGG pixels arranged in 20 $$times$$ 20 matrix to form a scintillator block, which was optically coupled to a 1-inch-square position-sensitive photomultiplier tube. The GAGG detector was encased in a 20-mm-thick container and a pinhole collimator was mounted on its front. The gamma camera had spatial resolution of approximately 6.7 cm and sensitivity of 3.2 $$times$$ 10$$^{-7}$$ at 1.2 m from the collimator surface. The gamma camera was set 1 m from the 35 cm $$times$$ 35 cm $$times$$ 5 cm plastic phantom in the proton therapy treatment room, and proton beams were irradiated to the phantom with two proton energies. For both proton energies, positron distribution in the phantom could be imaged by the gamma camera with 10-min acquisition. The lengths of the range of protons measured from the images were almost identical to the calculation. These results indicate that the developed high-energy gamma camera is useful for imaging positron distributions in proton therapy.


Ultra-high resolution of radiocesium distribution detection based on Cherenkov light imaging

山本 誠一*; 緒方 良至*; 河地 有木; 鈴井 伸郎; 尹 永根; 藤巻 秀

Nuclear Instruments and Methods in Physics Research A, 777, p.102 - 109, 2015/03

 被引用回数:2 パーセンタイル:66.1(Instruments & Instrumentation)

After the nuclear disaster in Fukushima, radiocesium contamination became a serious scientific concern and research of its effects on plants increased. In such plant studies, high resolution images of radiocesium are required without contacting the subjects. Cherenkov light imaging of beta radionuclides has inherently high resolution and is promising for plant research. Since $$^{137}$$Cs and $$^{134}$$Cs emit beta particles, Cherenkov light imaging will be useful for the imaging of radiocesium distribution. Consequently, we developed and tested a Cherenkov light imaging system. We used a high sensitivity cooled charge coupled device (CCD) camera for imaging Cherenkov light from $$^{137}$$Cs and $$^{134}$$Cs. A bright lens was mounted on the camera and placed in a black box. With a 100-$$mu$$m $$^{137}$$Cs point source, we obtained 220-$$mu$$m spatial resolution in the Cherenkov light image. With a 1-mm diameter, 320-kBq $$^{137}$$Cs point source, the source was distinguished within 2-s. We successfully obtained Cherenkov light images of a plant whose root was dipped in a $$^{137}$$Cs solution, radiocesium-containing samples as well as line and character phantom images with our imaging system. Cherenkov light imaging is promising for the high resolution imaging of radiocesium distribution without contacting the subject.



西森 信行; 永井 良治; 松葉 俊哉; 羽島 良一; 山本 将博*; 宮島 司*; 本田 洋介*; 内山 隆司*; 飯島 北斗*; 栗木 雅夫*; et al.

Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (インターネット), p.174 - 178, 2014/06



Performance of a total absorption clover detector for $$Q_{beta}$$ measurements of neutron-rich nuclei far from the $$beta$$-stability line

林 裕晃*; 柴田 理尋*; 浅井 雅人; 長 明彦; 佐藤 哲也; 小泉 光生; 木村 敦; 大島 真澄*

Nuclear Instruments and Methods in Physics Research A, 747, p.41 - 51, 2014/05

 被引用回数:4 パーセンタイル:51.01(Instruments & Instrumentation)

短寿命核分裂生成核種の$$beta$$崩壊エネルギー$$Q_{beta}$$を高効率かつ高精度に測定するため、全吸収クローバー検出器を新たに開発し、その性能を評価した。中央に貫通孔がある大型のクローバー型Ge検出器を使うことで、極めて高効率かつ高エネルギー分解能で$$beta$$線と$$gamma$$線の全吸収スペクトルを測定し、$$Q_{beta}$$$$pm$$30keVの精度で決定できることを示した。この装置を用いて$$^{166}$$Eu, $$^{165}$$Gdの$$Q_{beta}$$を初めて決定し、$$^{160-165}$$Eu, $$^{163}$$Gdの$$Q_{beta}$$の精度を向上させた。また、$$^{163}$$Gdの核異性体準位を初めて観測し、そのエネルギーと半減期を決定した。


Experimental investigation of an optimum configuration for a high-voltage photoemission gun for operation at $$geq$$ 500 kV

西森 信行; 永井 良治; 松葉 俊哉; 羽島 良一; 山本 将博*; 本田 洋介*; 宮島 司*; 飯島 北斗*; 栗木 雅夫*; 桑原 真人*

Physical Review Special Topics; Accelerators and Beams, 17(5), p.053401_1 - 053401_17, 2014/05

 被引用回数:12 パーセンタイル:25.2(Physics, Nuclear)

We have demonstrated generation of a 500-keV electron beam from a high DC voltage photoemission gun for an energy recovery linac light source. This demonstration was achieved by addressing two discharge problems that lead to vacuum breakdown of the DC gun. One is field emission generated from a central stem electrode. The other is microdischarge at an anode electrode or a vacuum chamber, which is triggered by microparticle transfer or field emission from a cathode electrode. An experimental investigation has revealed that larger acceleration gap optimized to mainly reduce surface electric field of anode electrode results in suppression of the microdischarge events which accompany gas desorption. It has also been found that non evaporable getter pumps placed around the acceleration gap greatly help suppress those microdischarge events. The applied voltage as a function of the total gas desorption is shown to be a good measure to find the optimum DC gun configuration.


Three-layer GSO depth-of-interaction detector for high-energy gamma camera

山本 誠一*; 渡部 浩司*; 河地 有木; 藤巻 秀; 加藤 克彦*; 畑澤 順*

Nuclear Instruments and Methods in Physics Research A, 743, p.124 - 129, 2014/04

 被引用回数:8 パーセンタイル:25.28(Instruments & Instrumentation)

Using Ce-doped GSO of different Ce concentrations, three-layer depth-of-interaction (DOI) block detectors were developed to reduce the parallax error at the edges of a pinhole gamma camera for high-energy $$gamma$$ photons. GSOs with Ce concentrations of 1.5 mol%, 0.5 mol% crystal, 0.4 mol% were selected for the DOI detectors. These three types of GSOs were optically coupled in the depth direction, arranged in a 22 $$times$$ 22 matrix and coupled to a flat panel photomultiplier tube. With these combinations of GSOs, all spots corresponding to GSO cells were clearly resolved in the position histogram. Pulse shape spectra showed three peaks for these three decay times of GSOs. The block detector was contained in a tungsten shield, and a pinhole collimator was mounted. With pulse shape discrimination, we separated the point source images of the Cs-137 for each DOI layer. The point source image of the lower layer was detected at the most central part of the field-of-view (FOV), and the distribution was the smallest. The point source image of the higher layer was detected at the most peripheral part of the FOV, and the distribution was widest. With this information, the spatial resolution of the pinhole gamma camera can be improved. We conclude that DOI detection is effective for pinhole gamma cameras for high energy $$gamma$$ photons.


RI imaging method to analyze a process of radiocesium contamination of plants and to develop phytoremediation techniques

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

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 100, 2014/03

Because of the accident at the Fukushima Daiichi Nuclear Power Plant of the Tokyo Electric Power Company, Inc., an extensive area of agricultural fields was contaminated with radioactive materials. Cs-137 is the most of soil contaminant, which was reported to have a 16 - 18 years half-life in agricultural fields affected by physical decay and soil erosion. Therefore, further research is required on the behavior of radiocesium and its transfer from contaminated soil to agricultural products. In this study, we have developed a gamma camera for $$gamma$$ ray imaging of Cs-137 emitting at 662 keV. A pinhole collimator was fabricated with heavy metal of tungsten to avoid the penetration and scattering of $$gamma$$ rays, since high-energy incident $$gamma$$ ray originates from Cs-137 tracer inside a test plant. A gadolinium oxyorthosilicate (GSO) scintillator and a flat panel position sensitive photomultiplier tube were adapted to the gamma camera to obtain adequate high sensitivity. Giant knotweed, which has potential as a cleanup plant with high uptake capacity for cesium, was grown in hydroponic solutions. After exposed to approximately 400 kBq of Cs-137, images were taken for 15 h. Sequential images reveal the changing distribution of cesium into the plant from the hydroponic solutions via the root system. We have indicated real-time visualization of uptake of radiocesium within an intact plant in the first time successfully.


Effect of resistivity profile on current decay time of initial phase of current quench in neon-gas-puff inducing disruptions of JT-60U

河上 翔*; 柴田 欣秀; 渡邊 清政*; 大野 哲靖*; 諫山 明彦; 滝塚 知典*; 河野 康則; 岡本 征晃*

Physics of Plasmas, 20(11), p.112507_1 - 112507_6, 2013/11

 被引用回数:2 パーセンタイル:86.64(Physics, Fluids & Plasmas)



Progress in a photocathode DC gun at the compact ERL

西森 信行; 永井 良治; 松葉 俊哉; 羽島 良一; 山本 将博*; 本田 洋介*; 宮島 司*; 飯島 北斗*; 栗木 雅夫*; 桑原 真人*

Proceedings of 35th International Free-Electron Laser Conference (FEL 2013) (Internet), p.184 - 188, 2013/08

Photocathode DC gun to produce a train of electron bunch at high-average current and small emittance is a key component of advanced accelerators for high-power beams. However, DC guns operated at a voltage above 350 kV have suffered from field emitted electrons from a support rod since the development of Lasertron in 1980's. This critical issue has been resolved by a novel configuration, segmented insulator and guard rings, adopted in a DC gun at JAEA and stable application of high voltage at 550 kV has been demonstrated. The gun has been installed at the Compact ERL at KEK and ready for the beam generation. Similar type of DC guns are under development at KEK, Cornell, JLAB and IHEP. In this talk, we present progress in photocathode DC gun for high voltage and small emittance.



西森 信行; 永井 良治; 松葉 俊哉; 羽島 良一; 山本 将博*; 宮島 司*; 本田 洋介*; 飯島 北斗*; 栗木 雅夫*; 桑原 真人*; et al.

Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (インターネット), p.255 - 259, 2013/08



Fast neutron detection under intense $$gamma$$-ray fields with novel nuclear emulsion technique

石原 康平*; 高木 恵輔*; 湊 春奈*; 河原林 順*; 富田 英生*; 前田 茂貴; 中 竜大*; 森島 邦博*; 中野 敏行*; 中村 光廣*; et al.

Radiation Measurements, 55, p.79 - 82, 2013/08

 パーセンタイル:100(Nuclear Science & Technology)



Generation of a 500-keV electron beam from a high voltage photoemission gun

西森 信行; 永井 良治; 松葉 俊哉; 羽島 良一; 山本 将博*; 宮島 司*; 本田 洋介*; 飯島 北斗*; 栗木 雅夫*; 桑原 真人*

Applied Physics Letters, 102(23), p.234103_1 - 234103_4, 2013/06

 被引用回数:12 パーセンタイル:44.55(Physics, Applied)

High-brightness and high-current electron guns for the future light sources such as energy recovery linac light sources and high repetition rate X-ray free electron lasers require exit beam energy of 500 keV or more to reduce space charge induced emittance growth in a drift space from the gun exit to the following superconducting accelerator entrance. At Japan Atomic Energy Agency, we have developed a DC photoemission gun employing a segmented insulator to mitigate the field emission problem, that is a major obstacle for the DC gun from being operated at 500 kV or more. Recent results of generating 500 keV electron beam with current up to 1.8 mA is presented.

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