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論文

Magnetic excitation in the =1/2 Ising-like antiferromagnetic chain CsCoCl $_{3}$ in longitudinal magnetic fields studied by high-field ESR measurements

木村尚次郎*; 大西弘明; 奥西巧一*; 赤木暢*; 鳴海康雄*; 萩原政幸*; 金道浩一*; 菊池彦光*

Journal of the Physical Society of Japan, 92(9), p.094701_1 - 094701_9, 2023/09

https://doi.org/10.7566/JPSJ.92.094701

被引用回数：0 パーセンタイル：0(Physics, Multidisciplinary)

High-field electron spin resonance (ESR) measurements were performed on the =1/2 Ising-like antiferromagnetic chain CsCoCl $_{3}$ in the frequency range up to 4.4THz and magnetic fields for up to 53T. We observed softening of the spinon excitation, which drives the spin chain into the quantum critical state at the critical field $H_{c}$ =33.0T. Above $H_{c}$ , we observed the string excitation at the wave number =, which is characteristic of the =1/2 spin chain in the quantum critical state in the magnetic fields. We also observed a crossover of the string excitation to the magnon bound state above the saturation fields $H_{s}$ =43.9T upon increasing the magnetic fields. Finally, we discuss how the string excitation and magnon bound state can be excited by the electric dipole transition due to spin quadrupolar resonance.

論文

One-dimensional band structure in quasi-two-dimensional -MoO $_{11}$ revealed by angle-resolved photoelectron spectroscopy and first-principles calculation

角田一樹; 檜垣聡太*; 佐藤仁*; 水流大地*; 宮本幸治*; 奥田太一*; 黒岩芳弘*; 森吉千佳子*; 高瀬浩一*; 小口多美夫*; et al.

Journal of the Physical Society of Japan, 92(8), p.084706_1 - 084706_6, 2023/08

https://doi.org/10.7566/JPSJ.92.084706

被引用回数：0 パーセンタイル：0(Physics, Multidisciplinary)

We investigated the electronic structure of -MoO $_{11}$ bulk crystal in the whole Brillouin zone at a normal metallic state by utilizing resonant and angle-resolved photoelectron spectroscopies and first-principles calculations. Mo 4-4 resonant photoelectron experiment revealed that the Mo 4 electrons of MoO octahedra mainly contributed to the electrical conductivity. We also demonstrated that the free electron-like band dispersions along axis, consisting of Mo 4 $d_{xy}$ electrons, do not show clear and dependences and formed a one-dimensional Fermi surface even at the normal state. The observed low-dimensional and anisotropic band structures are expected to induce exotic physical properties such as quantized bulk Hall effect, charge density wave transitions, and Luttinger liquid behavior.

論文

Optical selection rules of the magnetic excitation in the = $frac{1}{2}$ one-dimensional Ising-like antiferromagnet BaCo $_{2}$ V $_{2}$ O $_{8}$

木村尚次郎*; 大西弘明; 奥谷顕*; 赤木暢*; 鳴海康雄*; 萩原政幸*; 奥西巧一*; 金道浩一*; He, Z.*; 谷山智康*; et al.

Physical Review B, 105(1), p.014417_1 - 014417_9, 2022/01

https://doi.org/10.1103/PhysRevB.105.014417

被引用回数：3 パーセンタイル：34.67(Materials Science, Multidisciplinary)

In this study, we clarify the selection rules of optical transitions from the ground state to the magnetic excited states in the quasi-one-dimensional quantum Ising-like antiferromagnet BaCo $_{2}$ V $_{2}$ O $_{8}$ with spin = $frac{1}{2}$ using the high-field electron spin resonance measurement with illuminating polarized electromagnetic waves. We demonstrate that the unconventional magnetic excitation via the pair creation of quasipaticles at wave numbers $q_{z}=pi/2$ and in the field-induced quantum critical state can couple with both oscillating magnetic and electric fields. Our density matrix renormalization group calculations indicate that the observed selection rules can be explained by two- and four-fold periodical spin interactions, originating from the screw chain structure in BaCo $_{2}$ V $_{2}$ O $_{8}$ , in addition to the magnetoelectric coupling between spins and electric dipoles.

論文

Spin excitations of the =1/2 one-dimensional Ising-like antiferromagnet BaCo $_{2}$ V $_{2}$ O $_{8}$ in transverse magnetic fields

奥谷顕*; 大西弘明; 木村尚次郎*; 竹内徹也*; 木田孝則*; 森道康; 三宅厚志*; 徳永将史*; 金道浩一*; 萩原政幸*

Journal of the Physical Society of Japan, 90(4), p.044704_1 - 044704_9, 2021/04

https://doi.org/10.7566/JPSJ.90.044704

被引用回数：3 パーセンタイル：30.35(Physics, Multidisciplinary)

The high-field multifrequency electron spin resonance (ESR), the magnetization, and the specific heat of single crystals of BaCo $_{2}$ V $_{2}$ O $_{8}$ (a quasi-one-dimensional Ising-like antiferromagnet with ) were measured in two different transverse magnetic fields: and . A softening of the lowest ESR mode was observed near the saturation field of the magnetization around 40 T in , whereas it occurs around 10 T in , far below the saturation field. These observations were reproduced by numerical calculations using the density-matrix renormalization group methods, including the staggered magnetic fields induced by a uniform external magnetic field and the interchain magnetic exchange interaction. We found that the directional dependence of the lowest mode originates mainly from the remarkable angular dependence of the induced magnetic field. The interchain interaction is also quantitatively important for reproducing the experimental results. The directional dependence of the lowest mode is demonstrated by the particle-hole excitation of spinons using the Jordan-Wigner transformation.

論文

Nitrogen hot trap design and manufactures for lithium test loop in IFMIF/EVEDA project

若井栄一; 渡辺一慶*; 伊藤譲*; 鈴木晶大*; 寺井隆幸*; 八木重郎*; 近藤浩夫; 金村卓治; 古川智弘; 平川康; et al.

Plasma and Fusion Research (Internet), 11, p.2405112_1 - 2405112_4, 2016/11

BB2015-1982.pdf:2.03MB

http://doi.org/10.1585/pfr.11.2405112

The lithium target facility of IFMIF (International Fusion Materials Irradiation Facility) consists of target assembly, lithium main loop, lithium purification loops, the diagnostic systems, and remote handling system. Major impurities in the lithium loop are proton, deuterium, tritium, 7-Be, activated corrosion products and the other species (C, N, O). It is very important to remove nitrogen content in lithium loop during operation, in order to avoid the corrosion/erosion of the nozzle of lithium target for the stable lithium flow on the target assembly. Nitrogen in the lithium can be removed by N hot trap using Fe-5at%Ti alloy at temperatures from 400 to 600 $^{circ}$ C. In this study, the specification and the detailed design were evaluated, and the component of N hot trap system was fabricated.

論文

High order harmonics from relativistic electron spikes

Pirozhkov, A. S.; 神門正城; Esirkepov, T. Z.; Faenov, A. Y.*; Pikuz, T. A.*; 河内哲哉; 匂坂明人; Koga, J. K.; 森道昭; 川瀬啓悟*; et al.

RAL-TR-2015-025, P. 22, 2015/00

https://www.clf.stfc.ac.uk/Pages/2014-15.aspx

We provide a description of experiments performed with the J-KAREN and Astra Gemini lasers where we discovered a new regime of relativistic high-order harmonic generation by multi-terawatt femtosecond lasers in gas targets. The results were explained using particle-in-cell simulations and catastrophe theory. Our work paves the way towards a bright coherent X-ray source based on compact lasers and accessible, repetitive, and debris-free gas jet targets. Such a source will be crucial for fundamental research and numerous applications requiring pumping, probing, imaging of microscopic objects and for attosecond science.

論文

High order harmonics from relativistic electron spikes

Pirozhkov, A. S.; 神門正城; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T. A.*; 河内哲哉; 匂坂明人; et al.

New Journal of Physics (Internet), 16(9), p.093003_1 - 093003_30, 2014/09

https://doi.org/10.1088/1367-2630/16/9/093003

被引用回数：30 パーセンタイル：81.06(Physics, Multidisciplinary)

We present a detailed description of our discovery of a new regime of high-order harmonic generation, including experimental data, simulations, and description of new harmonic generation mechanism. The harmonics are generated by multi-terawatt relativistic-irradiance ( 10 $^{18}$ W/cm) femtosecond ( 30-50 fs) lasers focused to gas jet targets. According to our model, the harmonics are produced by sharp, structurally stable, oscillating electron spikes at the joint of boundaries of wake and bow waves excited by the laser pulse.

論文

Transmission secondary ion mass spectrometry using 5 MeV C $_{60}$ $^{+}$ ions

中嶋薫*; 永野賢悟*; 鈴木基史*; 鳴海一雅; 齋藤勇一; 平田浩一*; 木村健二*

Applied Physics Letters, 104(11), p.114103_1 - 114103_4, 2014/03

https://doi.org/10.1063/1.4868655

被引用回数：6 パーセンタイル：26.85(Physics, Applied)

In the secondary ion mass spectrometry (SIMS), use of cluster ions has an advantage of having a high sensitivity of intact large molecular ions over monatomic ions. This paper presents further yield enhancement of the intact biomolecular ions with measuring the secondary ions emitted from a self-supporting thin film in the forward direction, which is the same direction as primary beams. Phenylalanine amino-acid films deposited on self-supporting thin Si $_{3}$ N $_{4}$ films were bombarded with 5-MeV C $_{60}$ $^{+}$ ions. Secondary ions emitted in the forward and backward directions were measured under the bombardments of the SiN and phenylalanine sides, respectively. The yield of intact phenylalanine molecular ions emitted in the forward direction is about one order of magnitude larger than the backward direction, while fragment ions of phenylalanine molecules are suppressed. This suggests a large potential of transmission cluster-ion SIMS for the analysis of biological materials.

論文

Relativistic high harmonic generation in gas jet targets

Pirozhkov, A. S.; 神門正城; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; 河内哲哉; 匂坂明人; et al.

AIP Conference Proceedings 1465, p.167 - 171, 2012/07

https://doi.org/10.1063/1.4737557

被引用回数：1 パーセンタイル：46.45(Physics, Applied)

We experimentally demonstrate new regime of high-order harmonic generation by relativistic-irradiance lasers in gas jet targets. Bright harmonics with both the odd and even orders are emitted in the forward direction, while the base harmonic frequency is downshifted. The harmonics are generated by linearly as well as circularly polarized pulses. With the 9 TW laser, the harmonics reach 360 eV, within the "water window" spectral region. Using 120 TW laser producing 40 uJ/sr per harmonic at 120 eV, we demonstrate the photon number scalability. The experimentally demonstrated harmonics cannot be explained by previously known mechanisms. We introduce a novel high-order harmonics generation mechanism, which explains our experimental findings.

論文

High-order harmonics from bow wave caustics driven by a high-intensity laser

Esirkepov, T. Z.; Pirozhkov, A. S.; 神門正城; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A.*; Pikuz, T.; 河内哲哉; 匂坂明人; et al.

AIP Conference Proceedings 1465, p.172 - 180, 2012/07

https://doi.org/10.1063/1.4737558

被引用回数：0 パーセンタイル：0.13(Physics, Applied)

最近の実験で観測されたテラワットレーザーによるXUV領域の高次高調波の発生のメカニズムに関し、カタストロフィー理論を利用した船首波によるメカニズムを考案し、2DPIC計算と3DPIC計算によりその妥当性を確認した。これにより、この高次高調波生成メカニズムに基づいた、新しいXUV光及びX線源を提案した。

論文

Complementary characterization of radioactivity produced by repetitive laser-driven proton beam using shot-to-shot proton spectral measurement and direct activation measurement

小倉浩一; 静間俊行; 早川岳人; 余語覚文; 西内満美子; 織茂聡; 匂坂明人; Pirozhkov, A. S.; 森道昭; 桐山博光; et al.

Japanese Journal of Applied Physics, 51(4), p.048003_1 - 048003_2, 2012/04

https://doi.org/10.1143/JJAP.51.048003

被引用回数：2 パーセンタイル：8.93(Physics, Applied)

繰り返し動作(1Hz)可能な高強度レーザーを用いて高エネルギーのプロトンを発生した。そのプロトンをリチウムターゲットに照射し、 $^{7}$ Li(p,n) $^{7}$ Be反応を起こした。反応によって生成した $^{7}$ BeをGe半導体検出器を用いて測定した。その結果、1.70.2Bqが生成したことがわかった。一方、生成したプロトンのスペクトルを飛行時間法を用いて測定し、放射化断面積を用いて放射化量を評価した。その結果、1.60.3Bqが得られた。誤差範囲で一致した。そこで、われわれは、レーザー駆動粒子線を用いて放射化反応を起こさせる場合、反応量を飛行時間法でレーザーショットごとにモニターする方法を提案する。

論文

Soft-X-ray harmonic comb from relativistic electron spikes

Pirozhkov, A. S.; 神門正城; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; 河内哲哉; 匂坂明人; et al.

Physical Review Letters, 108(13), p.135004_1 - 135004_5, 2012/03

https://doi.org/10.1103/PhysRevLett.108.135004

被引用回数：69 パーセンタイル：90.73(Physics, Multidisciplinary)

マルチテラワットレーザーをガスジェットターゲットに集光照射することにより「水の窓」に達する高次高調波発生を実験で示すことに成功した。数百次に達する高次高調波の強さはJ/srパルスと評価できる。このような高調波は、高強度レーザーパルスが低密度プラズマ中を相対論的な自己収束を伴って伝搬する際に、パルスによって励起される尖塔波とキャビテーションの境界の交差点で発生する電子スパイクのコヒーレント振動により生じる。このときのスパイクの先鋭さと安定度はカタスロトフ理論により説明される。発生機構はPICシミュレーションによっても確認された。

報告書

幌延深地層研究計画換気立坑先行ボーリング(PB-V01孔)調査報告書; 物理検層

舟木泰智; 浅森浩一; 真田祐幸; 羽出山吉裕*; 山本卓也*; 井尻裕二*; 松岡清幸*; 木村和洋*; Lin, S.*; 熊谷敏文*

JAEA-Data/Code 2010-002, 151 Pages, 2010/06

JAEA-Data-Code-2010-002.pdf:43.13MB

原子力機構は、高レベル放射性廃棄物の地層処分技術に関する研究開発として、地下研究施設の建設を伴う研究プロジェクト(幌延深地層研究計画)を進めている。幌延深地層研究計画において建設中の地下研究施設のうち、換気立坑の施工における、湧水抑制対策の施工計画並びに排水処理設備の増設計画の策定を主な目的として、2007年10月から2008年3月にかけて、換気立坑近傍にて換気立坑先行ボーリング(PB-V01孔)を実施した。本報告書は、換気立坑先行ボーリング(PB-V01孔)で実施した調査のうち、物理検層(温度検層,音波検層,キャリパー検層,超音波型孔壁画像検層,ヒートパルス型フローメーター検層及びセメントボンド検層)の結果をデータ集として取りまとめたものである。

論文

Simulation and experiments of the laser induced breakdown of air for femtosecond to nanosecond order pulses

Koga, J. K.; 森林健悟; 福田祐仁; Bulanov, S. V.; 匂坂明人; 小倉浩一; 大道博行; 山極満; 木村豊秋*; 藤川武敏*; et al.

Journal of Physics D; Applied Physics, 43(2), p.025204_1 - 025204_15, 2010/01

https://doi.org/10.1088/0022-3727/43/2/025204

被引用回数：17 パーセンタイル：56.56(Physics, Applied)

Three dimensional simulations and experimental results for the laser induced breakdown of air are presented. The simulations include the laser propagation, multi-photon and impact ionization, and heating of the electrons using accurate atomic and molecular data. For laser pulses of duration from 100 femto-seconds to 1 nano-second mechanisms for the breakdown of air based on the pulse duration and intensity ranging from optical field ionization to electron impact ionization are found. The laser energies at which the breakdown occurs are found to be in good agreement with experimental results.

論文

Experimental studies of the high and low frequency electromagnetic radiation produced from nonlinear laser-plasma interactions

神門正城; Pirozhkov, A. S.; 福田祐仁; Esirkepov, T. Z.; 大東出; 川瀬啓悟; Ma, J. L.*; Chen, L. M.*; 林由紀雄; 森道昭; et al.

European Physical Journal D, 55(2), p.465 - 474, 2009/09

https://doi.org/10.1140/epjd/e2009-00246-x

被引用回数：18 パーセンタイル：64.01(Optics)

高強度レーザーとプラズマの非線型な相互作用により、高エネルギーの粒子やX線からTHz領域までの光子が生成される。われわれの高周波電磁放射生成方法は、高強度超短パルスレーザーにより作られる航跡波に近赤外のレーザー光を相互作用させるものである。この飛翔鏡の原理検証実験についてレビューを行う。また、われわれの実験では同時に、低周波の電磁波生成も観測している。これはプラズマ中に生成されるソリトンからの電磁放射であると認識している。ソリトンは、不足密度プラズマ中で生成され、レーザー光のエネルギーの一部をレーザーと同一の偏光の低周波電磁波として閉じこめ、プラズマと真空の境界で電磁放射を行うものである。このソリトンからの低周波電磁波を偏光分解計測した結果を報告する。

論文

Demonstration of flying mirror with improved efficiency

Pirozhkov, A. S.; 神門正城; Esirkepov, T. Z.; 福田祐仁; Chen, L.-M.*; 大東出; 小倉浩一; 本間隆之; 林由紀雄; 小瀧秀行; et al.

AIP Conference Proceedings 1153, p.274 - 284, 2009/07

A strongly nonlinear breaking wake wave driven by an intense laser pulse can act as a partially reflecting relativistic mirror (the Flying Mirror). Upon reflection from such mirror, a counter-propagating optical-frequency laser pulse is directly converted into high-frequency radiation, with a frequency multiplication factor (the double Doppler effect). We present the results of recent experiment in which the photon number in the reflected radiation was more than times larger than in our proof-of-principle experiment. It is notable that the energy of laser was increased about three times. The Flying Mirror promises to generate intense coherent ultrashort XUV and X-ray pulses that inherit their temporal shape and polarization from the original optical-frequency (laser) pulses. Furthermore, the reflected radiation bears important information about the reflecting wake wave itself, which can be used for the diagnostics.

論文

Proton-induced nuclear reactions using compact high-contrast high-intensity laser

小倉浩一; 静間俊行; 早川岳人; 余語覚文; 西内満美子; 織茂聡; 匂坂明人; Pirozhkov, A. S.; 森道昭; 桐山博光; et al.

Applied Physics Express, 2(6), p.066001_1 - 066001_3, 2009/05

https://doi.org/10.1143/APEX.2.066001

被引用回数：14 パーセンタイル：49.78(Physics, Applied)

強度10 $^{20}$ W/cm $^{2}$ のレーザー光(10Hz,小型高コントラスト高強度レーザー)をポリイミドテープ(7.5m)に集光することによって最大3.5MeVのプロトンを生成した。このプロトンで $^{11}$ B(p,n) $^{11}$ C反応を起こした。その結果、60ショットで11.1Bqの放射能を得た。薄層放射化への応用の可能性について議論した。

論文

XUV and IR electromagnetic radiation from nonlinear laser-plasma interaction

神門正城; Pirozhkov, A. S.; 福田祐仁; Esirkepov, T. Z.; 大東出; 川瀬啓悟; Ma, J.-L.; Chen, L.-M.; 林由紀雄; 森道昭; et al.

Harnessing Relativistic Plasma Waves as Novel Radiation Sources from Terahertz to X-Rays and Beyond (Proceedings of SPIE Vol.7359), p.73590K_1 - 73590K_11, 2009/05

https://doi.org/10.1117/12.820463

被引用回数：0 パーセンタイル：0.07(Optics)

Electromagnetic wave generation at the extreme ultraviolet (XUV) and infrared (IR) wavelength range is described through the interaction of intense short laser pulses with underdense plasmas. XUV pulses are generated through a laser light reflection from a relativistically moving electron dense shells (flying mirrors). A proof-of-principle and an advanced experiment of flying mirrors are presented. Both of the experiments demonstrated light reflection and frequency upshift in the XUV wavelength range (14-20 nm). The advanced experiment with a head-on collision of two laser pulses exhibited the high reflected photon number. IR radiation, which is observed in the forward direction, has the wavelength of 5 m and the same polarization as the driving laser dominantly. The source of the IR radiation is attributed to emission from relativistic solitons formed in underdense plasma.

論文

Longitudinal spin density wave order in a quasi-1D Ising-like quantum antiferromagnet

木村尚次郎*; 松田雅昌; 益田隆嗣*; 本堂英*; 金子耕士; 目時直人; 萩原政幸*; 竹内徹也*; 奥西巧一*; He, Z.*; et al.

Physical Review Letters, 101(20), p.207201_1 - 207201_4, 2008/11

https://doi.org/10.1103/PhysRevLett.101.207201

被引用回数：51 パーセンタイル：86.19(Physics, Multidisciplinary)

擬一次元イジング的量子反強磁性体BaCoVOの中性子回折実験を行い、磁場中で新しいタイプの非整合磁気秩序が現れることを観測した。この秩序は本質的に古典系で予想されるネール秩序とは異なり、量子スピン鎖特有の量子揺らぎに起因する。ギャップレス量子一次元系に特徴的な朝永-ラッティンジャー液体的性質が非整合磁気秩序を引き起こしている。

論文

New method to measure the rise time of a fast pulse slicer for laser ion acceleration research

森道昭; 余語覚文; 桐山博光; 西内満美子; 小倉浩一; 織茂聡; Ma, J.*; 匂坂明人; 金沢修平; 近藤修司; et al.

IEEE Transactions on Plasma Science, 36(4), p.1872 - 1877, 2008/08

https://doi.org/10.1109/TPS.2008.2000886

被引用回数：7 パーセンタイル：28.47(Physics, Fluids & Plasmas)

本グループでは、京都大学・電力中央研究所・GIST等と共同でレーザー駆動プロトンビームの利用に向け、レーザー・ターゲット双方からエネルギー/変換効率/Emittanceの最適化に関する研究を進めている。本論文はその研究の過程において開発したレーザー駆動高エネルギープロトンビーム発生におけるチャープパルスを用いた高速パルススライサー装置の新たな性能評価法と、その後に行ったイオン加速実験に関する結果をまとめたものである。この研究開発によって、新手法の有意性を明らかにするとともに、プレパルスの抑制により最大2.3MeVのプロトンビームの発生を実証しプレパルスがプロトンビームの高エネルギー化に重要な役割を果たすことを明らかにした。