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論文

Extreme phonon anharmonicity underpins superionic diffusion and ultralow thermal conductivity in argyrodite Ag$$_{8}$$SnSe$$_{6}$$

Ren, Q.*; Gupta, M. K.*; Jin, M.*; Ding, J.*; Wu, J.*; Chen, Z.*; Lin, S.*; Fabelo, O.*; Rodriguez-Velamazan, J. A.*; 古府 麻衣子; et al.

Nature Materials, 22, p.999 - 1006, 2023/05

https://doi.org/10.1038/s41563-023-01560-x
 被引用回数：26 パーセンタイル：99.21(Chemistry, Physical)

Ultralow thermal conductivity and fast ionic diffusion endow superionic materials with excellent performance both as thermoelectric converters and as solid-state electrolytes. Yet the correlation and interdependence between these two features remain unclear owing to a limited understanding of their complex atomic dynamics. Here we investigate ionic diffusion and lattice dynamics in argyrodite Ag$$_{8}$$SnSe$$_{6}$$ using synchrotron X-ray and neutron scattering techniques along with machine-learned molecular dynamics. We identify a critical interplay of the vibrational dynamics of mobile Ag and a host framework that controls the overdamping of low-energy Ag-dominated phonons into a quasi-elastic response, enabling superionicity. Concomitantly, the persistence of long-wavelength transverse acoustic phonons across the superionic transition challenges a proposed 'liquid-like thermal conduction' picture. Rather, a striking thermal broadening of low-energy phonons, starting even below 50 K, reveals extreme phonon anharmonicity and weak bonding as underlying features of the potential energy surface responsible for the ultralow thermal conductivity ($$<$$ 0.5 Wm$$^{-1}$$K$$^{-1}$$) and fast diffusion. Our results provide fundamental insights into the complex atomic dynamics in superionic materials for energy conversion and storage.

論文

Two-step Mott transition in Ni(S,Se)$$_2$$; $$mu$$SR studies and charge-spin percolation model

Sheng, Q.*; 金子 竜也*; Yamakawa, Kohtaro*; Guguchia, Z.*; Gong, Z.*; Zhao, G.*; Dai, G.*; Jin, C.*; Guo, S.*; Fu, L.*; et al.

Physical Review Research (Internet), 4(3), p.033172_1 - 033172_14, 2022/09

https://doi.org/10.1103/PhysRevResearch.4.033172

A pyrite system NiS$$_{2-x}$$Se$$_x$$ exhibits a bandwidth controlled Mott transition via (S,Se) substitutions in a two-step process: the antiferromagnetic insulator (AFI) to antiferromagnetic metal (AFM) transition at $$xsim$$0.45 followed by the AFM to paramagnetic metal (PMM) transition at $$xsim$$1.0. Among a few other Mott systems which exhibit similar two-step transitions, Ni(S,Se)$$_2$$ is of particular interest because a large intermediate AFM region in the phase diagram would provide unique opportunities to study the interplay between the spin and charge order. By comparing and combining our muon spin relaxation studies and previous neutron scattering studies, here we propose a picture where the spin order is maintained by the percolation of "nonmetallic" localized and dangling Ni moments surrounded by S, while the charge transition from AFI to AFM is caused by the percolation of the conducting paths generated by the Ni-Se-Ni bonds.

論文

Magnetic properties and electronic configurations of Mn ions in the diluted magnetic semiconductor Ba$$_{1-x}$$K$$_x$$(Zn$$_{1-y}$$Mn$$_y$$)$$_2$$As$$_2$$ studied by X-ray magnetic circular dichroism and resonant inelastic X-ray scattering

鈴木 博人*; Zhao, G.*; 岡本 淳*; 坂本 祥哉*; Chen, Z.-Y.*; 野中 洋亮*; 芝田 悟朗; Zhao, K.*; Chen, B.*; Wu, W.-B.*; et al.

Journal of the Physical Society of Japan, 91(6), p.064710_1 - 064710_5, 2022/06

https://doi.org/10.7566/JPSJ.91.064710
 被引用回数：0 パーセンタイル：0(Physics, Multidisciplinary)

The magnetic properties and the electronic excitations of the new diluted magnetic semiconductor Ba$$_{1-x}$$K$$_x$$(Zn$$_{1-y}$$Mn$$_y$$)$$_2$$As$$_2$$ have been studied by X-ray magnetic circular dichroism (XMCD) and resonant inelastic X-ray scattering (RIXS). The sum rule analysis of the XMCD spectra indicates that the Mn atoms are in the high-spin configurations of $$d^5$$, whereas the presence of competing ferromagnetic and antiferromagnetic interactions between the Mn ions reduces the net spin moment. Based on a comparison of the RIXS line shapes with those of Ga$$_{1-x}$$Mn$$_x$$As, it is concluded that the ground state of Mn in Ba$$_{1-x}$$K$$_x$$(Zn$$_{1-y}$$Mn$$_y$$)$$_2$$As$$_2$$ consists of both the $$3d^5 underline{L}$$ and $$3d^5$$ electron configurations.

論文

Synthesis and characterisation of a new graphitic C-S compound obtained by high pressure decomposition of CS$$_2$$

Klotz, S.*; Baptiste, B.*; 服部 高典; Feng, S. M.*; Jin, Ch.*; B$'e$neut, K.*; Guigner, J. M.*; Est$`e$ve, I.*

Carbon, 185, p.491 - 500, 2021/11

https://doi.org/10.1016/j.carbon.2021.09.048
 被引用回数：1 パーセンタイル：6.01(Chemistry, Physical)

二硫化炭素(CS$$_2$$)は、その最も近い類似体であるCO$$_2$$とともに、二重共有結合からなる最も単純な分子系の一つである。高圧下では、この分子構造は分解され、拡張された結晶性またはポリマー性の固体を形成すると考えられる。ここでは、大容量高圧技術を用いて300Kで約10GPa (100kbar)まで圧縮することにより、瞬間的な反応で純粋な硫黄とC$$_2$$Sに近い化学組成を持つ化合物の混合体が得られ、常圧まで回収できることを示している。中性子回折,X線回折,ラマン測定の結果、この物質は硫黄がナノメートルオーダーのsp$$^2$$グラファイト層に結合していることがわかった。電気抵抗の温度依存性からこの化合物は45meVのギャップを持つ半導体であることが明らかになった。200$$^{circ}$$C以上の温度でアニールすることで、硫黄含有量をC$$_{10}$$Sまで減らすことができた。この物質の構造的・電子的特性は、過去に行われたCS$$_2$$の高圧実験で報告された「ブリッジマンブラック」とは根本的に異なる。

論文

The $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross section from the surrogate ratio method and its effect on the $$^{60}$$Fe nucleosynthesis

Yan, S. Q.*; Li, X. Y.*; 西尾 勝久; Lugaro, M.*; Li, Z. H.*; 牧井 宏之; Pignatari, M.*; Wang, Y. B.*; Orlandi, R.; 廣瀬 健太郎; et al.

Astrophysical Journal, 919(2), p.84_1 - 84_7, 2021/10

https://doi.org/10.3847/1538-4357/ac12ce
 被引用回数：1 パーセンタイル：8.53(Astronomy & Astrophysics)

The long-lived $$^{60}$$Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe on $$^{59}$$Fe (half-life=44.5 days) is the key reaction for the production of $$^{60}$$Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1 $$gamma$$-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5$$pm$$3.5 mb at $$kT$$ = 30 keV and 13.4$$pm$$1.7 mb at $$kT$$ = 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of $$^{60}$$Fe from the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe rate are at most 25$$%$$. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of $$^{60}$$Fe.

論文

Spin Hall magnetoresistance in Pt/Cr$$_2$$O$$_3$$/YIG structure

Qi, J.*; Hou, D.*; Chen, Y.*; 齊藤 英治; Jin, X.*

Journal of Magnetism and Magnetic Materials, 534, p.167980_1 - 167980_6, 2021/09

https://doi.org/10.1016/j.jmmm.2021.167980
 被引用回数：1 パーセンタイル：7.51(Materials Science, Multidisciplinary)

Temperature dependence of the spin Hall magnetoresistance (SMR) has been investigated herein Pt/Cr$$_2$$O$$_3$$/Y$$_3$$Fe$$_5$$O$$_{12}$$ structure. Well below the N$'{e}$el temperature of Cr$$_2$$O$$_3$$, the SMR is not observed at the noise level of 1.2 ppm. In vicinity of the N$'{e}$el temperature, only a positive SMR tracks the YIG magnetic switching process, supporting that the SMR of normal metal/antiferromagnetic insulator/ferromagnetic insulator trilayer is controlled by the N$'{e}$el vector of the antiferromagnetic insulator. A high field magnetoresistance is observed up to an external magnetic field of 20000 Oe which has a field angle dependence symmetry consistent with the SMR. We attribute this high field magnetoresistance to be induced by the Hanle magnetoresistance in Pt.

論文

NIBS 2020 reference sheets

Sarmento, T.*; W$"u$nderlich, D.*; Fantz, U.*; Friedl, R.*; Rauner, D.*; 津守 克嘉*; Shenjin, L.*; Chen, W.*; Bollinger, D.*; 小栗 英知; et al.

AIP Conference Proceedings 2373, p.110001_1 - 110001_18, 2021/08

https://doi.org/10.1063/5.0057732

NIBS 2020に参加した世界中の研究機関の負水素イオン源の状況及びそれらを用いた核融合及び加速器研究施設の情報をまとめた。

論文

Crystalline dependence of spin transmission in Cr$$_2$$O$$_3$$ thin films

Qin, J.*; Hou, D.*; Chen, Y.*; 齊藤 英治; Jin, X.*

Journal of Magnetism and Magnetic Materials, 501, p.166362_1 - 166362_4, 2020/05

https://doi.org/10.1016/j.jmmm.2019.166362
 被引用回数：4 パーセンタイル：25.87(Materials Science, Multidisciplinary)

Spin transmission in Cr$$_2$$O$$_3$$ films of different crystalline textures is studied experimentally. With Y$$_3$$Fe$$_5$$O$$_{12}$$/Cr$$_2$$O$$_3$$/Pt trilayer devices, a spin current is injected into Cr$$_2$$O$$_3$$ by spin pumping from Y$$_3$$Fe$$_5$$O$$_{12}$$, and the spin transmission is monitored by the inverse spin Hall voltage ($$V_mathrm{ISHE}$$) in Pt. For (0001) plane textured Cr$$_2$$O$$_3$$ films, $$V_mathrm{ISHE}$$ vanishes quickly below the N$'{e}$el temperature. However, the $$V_mathrm{ISHE}$$ shows a broad shoulder below the N$'{e}$el temperature for $$(11bar{2}0)$$ and $$(11bar{2}3)$$ plane co-textured Cr$$_2$$O$$_3$$. Such a difference in the temperature dependence of Cr$$_2$$O$$_3$$ can be understood by the different N$'{e}$el vector orientations with respect to the injected spin moment direction.

論文

Strong local moment antiferromagnetic spin fluctuations in V-doped LiFeAs

Xu, Z.*; Dai, G.*; Li, Y.*; Yin, Z.*; Rong, Y.*; Tian, L.*; Liu, P.*; Wang, H.*; Xing, L.*; Wei, Y.*; et al.

npj Quantum Materials (Internet), 5(1), p.11_1 - 11_7, 2020/02

https://doi.org/10.1038/s41535-020-0212-x
 被引用回数：4 パーセンタイル：39.96(Materials Science, Multidisciplinary)

We use neutron scattering to study Vanadium (hole)-doped LiFe$$_{1-x}$$V$$_{x}$$As. In the undoped state, LiFeAs exhibits superconductivity at $$T_mathrm{c} = 18$$ K and transverse incommensurate spin excitations similar to electron overdoped iron pnictides. Upon Vanadium doping to form LiFe$$_{0.955}$$V$$_{0.045}$$, the transverse incommensurate spin excitations in LiFeAs transform into longitudinally elongated ones in a similar fashion to that of potassium (hole)-doped Ba$$_{0.7}$$K$$_{0.3}$$Fe$$_{2}$$As$$_{2}$$ but with dramatically enhanced magnetic scattering and elimination of superconductivity. This is different from the suppression of the overall magnetic excitations in hole-doped BaFe$$_{2}$$As$$_{2}$$ and the enhancement of superconductivity near optimal hole doping. These results are consistent with density function theory plus dynamic mean field theory calculations, suggesting that Vanadium doping in LiFeAs may induce an enlarged effective magnetic moment $$S_mathrm{eff}$$ with a spin crossover ground state arising from the inter-orbital scattering of itinerant electrons.

論文

IAEA Photonuclear Data Library 2019

河野 俊彦*; Cho, Y. S.*; Dimitriou, P.*; Filipescu, D.*; 岩本 信之; Plujko, V.*; Tao, X.*; 宇都宮 弘章*; Varlamov, V.*; Xu, R.*; et al.

Nuclear Data Sheets, 163, p.109 - 162, 2020/01

https://doi.org/10.1016/j.nds.2019.12.002
 被引用回数：83 パーセンタイル：99.67(Physics, Nuclear)

We report our coordinated efforts to address these data needs such as radiation shielding design and radiation transport analyses, and present the results of the new evaluations of more than 200 nuclides included in the new updated IAEA Photonuclear Data Library, where the photon energy goes up to 200 MeV. We discuss the new assessment method and make recommendations to the user community in cases where the experimental data are discrepant and the assessments disagree. In addition, in the absence of experimental data, we present model predictions for photon-induced reaction cross section on nuclides of potential interest to medical radioisotope production.

論文

Observation of $$tau^- rightarrow pi^- nu_{tau} e^+ e^- $$ and search for $$tau^- rightarrow pi^- nu_{tau} mu^+ mu^-$$

Jin, Y.*; 谷田 聖; Belle Collaboration*; 他198名*

Physical Review D, 100(7), p.071101_1 - 071101_9, 2019/10

https://doi.org/10.1103/PhysRevD.100.071101
 被引用回数：3 パーセンタイル：19.81(Astronomy & Astrophysics)

We present the first measurements of branching fractions of rare tau-lepton decays, $$tau^- rightarrow pi^- nu_{tau} ell^+ ell^-$$ ($$ell = e$$ or $$mu$$), using a data sample corresponding to 562 fb$$^{-1}$$ collected at a center-of-mass energy of 10.58 GeV with the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider. The $$tau^- rightarrow pi^- nu_tau e^+ e^-$$ decay is observed for the first time with 7.0$$sigma$$ significance. The partial branching fraction determined by the structure-dependent mechanisms mediated by either a vector or an axial-vector current for the mass region $$M_{pi e e} > 1.05$$ GeV/$$c^2$$ is measured to be $$mathcal{B}(tau^-rightarrow pi^- nu_tau e^+ e^-)[M_{pi^- e^+ e^-} > 1.05~{rm GeV}/c^2] = (5.90 pm 0.53 pm 0.85 pm 0.11) times 10^{-6}$$, where the first uncertainty is statistical, the second is systematic, and the third is due to the model dependence. In the full phase space, due to the different detection efficiencies for the structure-dependent mechanisms mediated by axial-vector and vector currents, the branching fraction varies from $$mathcal{B}_{A}(tau^-rightarrow pi^- nu_tau e^+ e^-) = (1.46 pm 0.13 pm 0.21) times 10^{-5}$$ to $$mathcal{B}_{V}(tau^-rightarrow pi^- nu_tau e^+ e^-) = (3.01 pm 0.27 pm 0.43) times 10^{-5}$$, respectively. An upper limit is set on the branching fraction of the $$tau^- rightarrow pi^- nu_tau mu^+ mu^-$$ decay, $$mathcal{B}(tau^-rightarrow pi^- nu_tau mu^+ mu^-) < 1.14 times 10^{-5}$$, at the 90% confidence level.

論文

Reduction of water content in calcium aluminate cement with/out phosphate modification for alternative cementation technique

Garcia-Lodeiro, I.*; 入澤 啓太; Jin, F.*; 目黒 義弘; 木下 肇*

Cement and Concrete Research, 109, p.243 - 253, 2018/07

https://doi.org/10.1016/j.cemconres.2018.04.019
 被引用回数：26 パーセンタイル：68.65(Construction & Building Technology)

Cementation of the secondary aqueous wastes from TEPCO Fukushima Daiichi Nuclear Power Plant is challenging due to the significant strontium content and radioactivity, leading to a potential risk of hydrogen gas generation via radiolysis of water content. The present study investigates the reduction of water content in calcium aluminate cement (CAC) with/out phosphate modification by a heat-treatment during the solidification. The reduction of water in the CAC was found restricted by the rapid formation of crystalline hydration phases, whereas the phosphate-modified system allowed the gradual reduction of water, achieving the reduction of 60% water content at 95$$^{circ}$$C. Curing at 60-95$$^{circ}$$C also eliminated the significant cracks found at 35$$^{circ}$$C in the phosphate system. The possible difference in the amorphous products, NaCaPO$$_{4}$$.nH$$_{2}$$O type at 35$$^{circ}$$C and Ca(HPO$$_{4}$$).xH$$_{2}$$O type at 60-95$$^{circ}$$C, may have contributed to the improvement in the microstructure together with the change in the pore size distribution.

論文

The CIELO collaboration; Progress in international evaluations of neutron reactions on Oxygen, Iron, Uranium and Plutonium

Chadwick, M. B.*; Capote, R.*; Trkov, A.*; Kahler, A. C.*; Herman, M. W.*; Brown, D. A.*; Hale, G. M.*; Pigni, M.*; Dunn, M.*; Leal, L.*; et al.

EPJ Web of Conferences, 146, p.02001_1 - 02001_9, 2017/09

https://doi.org/10.1051/epjconf/201714602001
 被引用回数：6 パーセンタイル：95.14(Nuclear Science & Technology)

CIELO共同研究では中性子断面積データの改善及びこれまでの評価で見られた断面積の不一致を解決することを目的として、原子力の臨界性に大きな影響を与える5核種($$^{16}$$O, $$^{56}$$Fe, $$^{235,238}$$U, $$^{239}$$Pu)の中性子断面積を評価している。この国際パイロットプロジェクトでは、経済協力開発機構・原子力機関・核データ評価国際協力ワーキングパーティに設置されたサブグループ40の下でIAEAからのサポートを受けて、実験並びに理論的な研究を活発に実施している。これらの研究を通じて測定データを精度よく反映し、さらに臨界性に関する積分テストで良い結果を示す新しい評価済ライブラリを開発している。

論文

Volume-wise destruction of the antiferromagnetic Mott insulating state through quantum tuning

Frandsen, B. A.*; Liu, L.*; Cheung, S. C.*; Guguchia, Z.*; Khasanov, R.*; Morenzoni, E.*; Munsie, T. J. S.*; Hallas, A. M.*; Wilson, M. N.*; Cai, Y.*; et al.

Nature Communications (Internet), 7, p.12519_1 - 12519_8, 2016/08

https://doi.org/10.1038/ncomms12519
 被引用回数：33 パーセンタイル：77.01(Multidisciplinary Sciences)

RENiO$$_3$$ (RE = rare-earth element) and V$$_2$$O$$_3$$ are archetypal Mott insulator systems. When tuned by chemical substitution (RENiO$$_3$$) or pressure (V$$_2$$O$$_3$$), they exhibit a quantum phase transition (QPT) between an antiferromagnetic Mott insulating state and a paramagnetic metallic state. Because novel physics often appears near a Mott QPT, the details of this transition, such as whether it is first or second order, are important. Here, we demonstrate through muon spin relaxation/rotation experiments that the QPT in RENiO$$_3$$ and V$$_2$$O$$_3$$ is first order: the magnetically ordered volume fraction decreases to zero at the QPT, resulting in a broad region of intrinsic phase separation, while the ordered magnetic moment retains its full value until it is suddenly destroyed at the QPT. These findings bring to light a surprising universality of the pressure-driven Mott transition, revealing the importance of phase separation and calling for further investigation into the nature of quantum fluctuations underlying the transition.

論文

Validation of nonlinear FEA models of a thin-walled elbow under extreme loading conditions for sodium-cooled fast reactors

渡壁 智祥; Jin, C.*; 臼井 嘉哉*; 酒井 新吉*; 若井 隆純; 大鹿 順司*; 月森 和之

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05

For the purpose of confirming failure modes and safety margin, some studies on the ultimate strength of thin-walled piping components for Sodium-cooled Fast Reactors (SFRs) under extreme loading conditions such as large earthquakes have been reported these several years. Nonlinear finite element analysis has been applied in these studies to simulate buckling and yielding with large deformation, whose accuracy is dependent on the element type, the mesh size, the elasto-plastic model and so on. It is important to check the validation of a finite element model for nonlinear analysis especially under extreme loading conditions. This paper presents static and dynamic analyses of a thin-walled elbow with large deformation under large seismic loading, and discusses the validation of the FEA models comparing with experimental results.

論文

Diluted ferromagnetic semiconductor Li(Zn,Mn)P with decoupled charge and spin doping

Deng, Z.*; Zhao, K.*; Gu, B.; Han, W.*; Zhu, J. L.*; Wang, X. C.*; Li, X.*; Liu, Q. Q.*; Yu, R. C.*; 後神 達郎*; et al.

Physical Review B, 88(8), p.081203_1 - 081203_5, 2013/08

https://doi.org/10.1103/PhysRevB.88.081203
 被引用回数：74 パーセンタイル：92.05(Materials Science, Multidisciplinary)

We report the discovery of a diluted magnetic semiconductor, Li(Zn,Mn)P, in which charge and spin are introduced independently via lithium off-stoichiometry and the isovalent substitution of Mn$$^{2+}$$ for Zn$$^{2+}$$, respectively. Isostructural to (Ga,Mn)As, Li(Zn,Mn)P was found to be a ${it p}$-type ferromagnetic semiconductor with excess lithium providing charge doping. First-principles calculations indicate that excess Li is favored to partially occupy the Zn site, leading to hole doping. Ferromagnetism with Curie temperature up to 34 K is achieved while the system still shows semiconducting transport behavior.

論文

Pressure effect on intersite charge transfer in A-site-ordered double-perovskite-structure oxide

Long, Y.-W.*; 川上 隆輝*; Chen, W.-T.*; 齊藤 高志*; 綿貫 徹; 中倉 勇太*; Liu, Q.-Q.*; Jin, C.-Q.*; 島川 祐一*

Chemistry of Materials, 24(11), p.2235 - 2239, 2012/06

https://doi.org/10.1021/cm301267e
 被引用回数：37 パーセンタイル：71.39(Chemistry, Physical)

Aサイト秩序ダブルペロブスカイト型酸化物のLaCu$$_{3}$$Fe$$_{4}$$O$$_{12}$$は、昇温によって大きく体積が減少する1次相転移が生じ、それがCuとFeイオン間の電荷移動によって引き起こされていることが知られている。本研究では室温で加圧することによっても同様の相転移が起こることを明らかにした。加えて、高圧相の方が体積弾性率が低くなるという通常ではみられない性質を示すことも明らかとなった。

論文

First neutral beam injection experiments on KSTAR tokamak

Jeong, S. H.*; Chang, D. H.*; Kim, T. S.*; In, S. R.*; Lee, K. W.*; Jin, J. T.*; Chang, D. S.*; Oh, B. H.*; Bae, Y. S.*; Kim, J. S.*; et al.

Review of Scientific Instruments, 83(2), p.02B102_1 - 02B102_3, 2012/02

https://doi.org/10.1063/1.3660254
 被引用回数：23 パーセンタイル：69.12(Instruments & Instrumentation)

KSTAR用中性粒子入射装置全体の1/3が2010年に完成し、入射実験を行った。この装置のイオン源は、原子力機構のプラズマ源とKAERIの多孔型加速電極で構成されている。入射実験前にイオン源の特性を調べ、ビーム発散角が0.8度、イオン組成比D$$^{+}$$/D$$_{2}$$$$^{+}$$/D$$_{3}$$$$^{+}$$が75:20:5、アーク効率1.0A/kWと良好な特性を確認した。KSTARへの入射実験では、0.7-1.5MWを70-90keVのエネルギーで入射した。プラズマのLモードからHモードへの遷移を確認でき、D-D反応による中性子発生を観測し、イオン温度とプラズマ閉じ込めエネルギーの上昇を観測した。

論文

Arc discharge characteristics of a long pulse ion source for the KSTAR neutral beam injector

Chang, D. H.*; Jeong, S. H.*; Jin, J. T.*; Chang, D. S.*; Kim, T. S.*; Lee, K. W.*; In, S. R.*; Oh, B. H.*; Bae, Y. S.*; Kim, J. S.*; et al.

Journal of the Korean Physical Society, 59(2), p.275 - 280, 2011/08

https://doi.org/10.3938/jkps.59.275
 被引用回数：3 パーセンタイル：27.45(Physics, Multidisciplinary)

KSTARの中性粒子入射装置(NBI)に向けて長パルスイオン源を開発し、イオン源のアーク放電特性を調べた。イオン源は、多極磁場型バケットタイプのプラズマ源と多数の円孔を配置した4枚のビーム加速電極から成る加速器で構成されている。安定で効率の良いアーク放電プラズマをアーク電源の一定パワーモード運転にて70kWまで生成することに成功した。アーク放電の安定な運転領域について、フィラメント加熱電圧,アーク電力、そして導入重水素ガスの量の変化に関して調べた。

論文

Li(Zn,Mn)As as a new generation ferromagnet based on a I-II-V semiconductor

Deng, Z.*; Jin, C. Q.*; Liu, Q. Q.*; Wang, X. C.*; Zhu, J. L.*; Feng, S. M.*; Chen, L. C.*; Yu, R. C.*; Arguello, C.*; 後神 達郎*; et al.

Nature Communications (Internet), 2, p.1425_1 - 1425_5, 2011/08

https://doi.org/10.1038/ncomms1425
 被引用回数：160 パーセンタイル：93.76(Multidisciplinary Sciences)

(Ga,Mn)Asは典型的な強磁性III-V族半導体として知られている。これは3価のGa原子を2価のMnで置き換えたものであるが、化学的溶解度が限られているため準安定であり、薄膜でしか製作できないものであった。また電子ドープも行うことができなかった。この困難な条件を超えるため、Masekらは理論的にI-II-V族半導体LiZnAsを提案した。この物質では原子価が等しい(Zn,Mn)の置き換えによる磁性の発現とLi濃度を過剰あるいは不足させることによるキャリアードープを独立に制御可能である。本研究では世界で初めてバルクな状態でのLi$$_{1+y}$$(Zn$$_{1-x}$$Mn$$_x$$)Asの合成に成功した。わずかにLiを過剰にすることで、50Kまでの温度で強磁性が現れること、またp型のキャリアーを持つことが観測され、これらの結果を報告した。

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