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論文

Dynamic properties of human $$alpha$$-synuclein related to propensity to amyloid fibril formation

藤原 悟*; 河野 史明*; 松尾 龍人*; 杉本 泰伸*; 松本 友治*; 成田 哲博*; 柴田 薫

Journal of Molecular Biology, 431(17), p.3229 - 3245, 2019/08

パーキンソン病発症には、脳細胞中の「$$alpha$$-シヌクレイン」というタンパク質が線維状に集合した状態(「アミロイド線維」と呼ばれる)となることが関係すると考えられており、どのようなメカニズムでこのアミロイド線維が形成されるのかに強い関心が寄せられています。そこで研究チームは、タンパク質分子の「動き」に着目し、アミロイド線維のできやすさが様々に異なった条件でのタンパク質の動きを、J-PARCの中性子準弾性散乱装置を用いて調べました。その結果、タンパク質分子の動きの違いによりアミロイド線維のできやすさが変わること、特にアミロイド線維ができるためには、タンパク質同士が集合しやすくなるような特定の動きが必要なことを明らかにしました。

論文

Turbulence intensity profile in high Reynolds number pipe flow

和田 裕貴; 古市 紀之*; 草野 英祐*; 辻 義之*

Proceedings of 11th International Symposium on Turbulence and Shear Flow Phenomena (TSFP-11) (Internet), 6 Pages, 2019/07

高レイノルズ数壁乱流における外層の乱流強度分布は対数関係を示すことが知られている。また、円管を除く境界層・チャネル乱流では内層の乱流強度のピーク値がレイノルズ数に依存して増加することが報告されているが、円管におけるそれらの傾向については実験データが乏しいことから未だに明らかになっていない。本発表では、高レイノルズ数円管乱流においてLDVにより取得した乱流強度分布をLDVの計測体積による空間分解能の影響を補正した結果を用い、内層の乱流強度のピーク値のレイノルズ数依存性について検討した結果を報告する。また、外層の対数関係についても先行研究結果との比較を行った結果を報告する。

論文

Longitudinal strain of epitaxial graphene monolayers on SiC substrates evaluated by $$z$$-polarization Raman microscopy

齊藤 結花*; 常磐 拳志郎*; 近藤 崇博*; Bao, J.*; 寺澤 知潮; 乗松 航*; 楠 美智子*

AIP Advances (Internet), 9(6), p.065314_1 - 065314_6, 2019/06

Longitudinal strains in epitaxial monolayer graphene (EMG) grown on SiC substrates were evaluated by $$z$$-polarization Raman microscopy. Due to the covalent bonds formed at the interface between graphene and the substrate, strong compressive strains were loaded on the EMG, which were sensitively detected by Raman spectroscopy. Our polarization Raman microscope was specially designed for evaluating the longitudinal ($$z$$-polarization) strain, as well as the lateral ($$xy$$-polarization). $$Z$$-polarization Raman microscopy revealed the relationship between the fluctuation of the local strains and the sample morphology in the SiC-graphene through submicron spatial resolution mapping. The amount of strain estimated through Raman shift and its spatial inhomogeneity have critical influence on the mobility of electrons, which are essential for future device applications of EMG.

論文

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

壁乱流における壁面近傍のLDV計測では相対的に測定体積が増大することにより乱流強度が過大評価されることが知られている。本発表では過大評価された測定値から真の乱流強度分布を推定する方法を提案する。円管乱流実験においてLDVでの測定位置を調整することにより相対的な測定体積を変化させて計測した乱流強度分布を用いて本補正法の妥当性について検証する。

論文

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

 パーセンタイル:100(Mechanics)

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.

論文

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.

論文

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.

論文

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:55.17(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.

論文

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:18.76(Materials Science, Multidisciplinary)

ダイバータ設計において、平衡コイルの配置を工夫してダイバータ板への磁力線の連結長を増加する「先進ダイバータ」の検討が注目されている。非常に大きな熱流の低減が求められる原型炉のダイバータ設計への適応を考察するため、コイル配置とプラズマ平衡配位の検討し1-2コのインターリンクコイルを設置することで、小型化したスーパーXダイバータ設計が可能であることを示した。さらに、上記のShort-SXDについてダイバータプラズマのシミュレーションを開始した。通常と異なるダイバータや磁力線の形状における計算用メッシュの作成を行い、500MWのプラズマ熱流が周辺部に排出される条件で、アルゴンガスを入射することで放射損失パワーを92%程度まで増加することにより、完全非接触ダイバータが生成する結果が得られた。標準磁場形状のダイバータでは同条件で完全非接触ダイバータは得らレなかったことから、磁場形状の工夫によるダイバータプラズマ制御の効果を明らかにした。最大ピーク熱負荷も標準形状のダイバータと比較して10MW/m$$^{-2}$$程度に低減できたが、プラズマ熱流よりも再結合プロセスが寄与するため、このプロセスのモデリング検討が重要と思われる。

論文

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.

論文

放射性セシウムの植物体内移行のガンマカメラによる解析

藤巻 秀

放射線と産業, (138), p.25 - 28, 2015/06

放射性セシウムが、植物体においてどのように吸収され、移行・集積するのかという動態とそのメカニズム、あるいはその動態を変化させるような栽培条件や遺伝的条件は、ほとんど未解明である。こうした問題に対し我々は、従来、植物ポジトロンイメージング技術を用いて関心元素の動態解明を行ってきたが、セシウム137はポジトロン放出核種ではないため、この技術を適用することができなかった。そこで我々は、植物研究用の感度や解像度を持ち、セシウム137からのエネルギーの高い$$gamma$$線を画像化することのできる、世界初のガンマカメラを開発した。これにより、福島県をはじめとする複数の県で基準値超えの収穫物が見つかったことが問題となっているダイズを対象に、セシウム137の動きを追ったところ、予想された葉にではなく、成長中の莢(種子)に集中して移行することが明らかになった。このことは、ある種の輸送メカニズムが働いていることを示唆している。今後、そのメカニズムを司る遺伝子が明らかになり、さらにそれを品種改良などで人為的に変えられれば、より安心なダイズ栽培ができると考えている。

論文

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:48.99(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.

論文

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:66.76(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.

論文

光陰極直流電子銃から500keV-mA電子ビームの生成

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

次世代ERL放射光源の電子源に対する要求は、エミッタンス0.1$$sim$$1mm-mrad電流10$$sim$$100mAの電子ビーム生成である。この低エミッタンスビーム生成には、空間電荷力抑制のため、電子銃の出射ビームエネルギー500keV以上が要求される。500kV光陰極DC電子銃が提案されて20年、運転電圧は放電問題のため350kVに留まってきた。われわれは、高電圧化を目標に掲げて電子銃開発に取り組んだ。まずガードリング付き分割型セラミック管を採用し、サポートロッドからの電界放出電子に起因する放電問題を解決した。次に、電子銃真空容器と陰極間の放電により、容器面上の残留微細粉塵が帯電し、陰極に付着した後に暗電流源となる現象が問題となった。これを解決するため、陰極-陽極のギャップ間隔を最適化し、特に真空容器表面の電界を下げる改造を行った。これにより電子ビーム生成条件下での550kV印加に初めて成功した。500keV電子ビーム生成試験を行った。波長530nmDCレーザー光をGaAs光陰極に照射し電子ビームを生成した。レーザー径0.1mm$$sigma$$、パワー1.5W、GaAs量子効率0.28%で最大1.8mAのビーム生成に成功した。

論文

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:51.53(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。

論文

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:23.42(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.

論文

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:25.95(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.

論文

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.

論文

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:86.48(Physics, Fluids & Plasmas)

JT-60Uでは、ネオンガスパフディスラプションの電流クエンチの初期フェイズにおけるプラズマ電流減衰時間は、内部インダクタンスの増加率によって大きく影響されることが分かっていた。このフェイズにおいて内部インダクタンスが増加する理由を調べるために、電子温度(抵抗率)分布と電流密度分布の時間変化に着目し、数値計算を実施した。その結果、内部インダクタンスが増加する理由を解明した。電流クエンチ開始直後の電流密度分布は、数値計算で得られる定常状態での電流密度分布より広い分布をしており、電流密度分布はその後中心ピークした形へ変化していき、それに伴い内部インダクタンスが増加することを明らかにした。

論文

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.

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