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論文

Efficient control and removal of laser-generated aerosol particles by combining water spray with pre-injection of electrical charged mist for nuclear reactor decommissioning

Xu, R.*; Sharma, A. K.*; Ahmed, Z.*; Kumar, R.*; Laffolley, H.; 横山 諒*; 三輪 修一郎*; 鈴木 俊一*; 小菅 淳

Nuclear Science and Techniques, 37(1), p.12_1 - 12_19, 2026/01

https://doi.org/10.1007/s41365-025-01825-x
 被引用回数：12 パーセンタイル：97.07(Nuclear Science & Technology)

Laser-induced aerosols, predominantly submicron in size, pose significant environmental and health risks during the decommissioning of nuclear reactors. This study experimentally investigated the removal of laser-generated aerosol particles using a water spray system integrated with an innovative system for pre-injecting electrically charged mist in our facility. To simulate aerosol generation in reactor decommissioning, a high-power laser was used to irradiate various materials (including stainless steel, carbon steel, and concrete), generating aerosol particles that were agglomerated with injected water mist and subsequently scavenged by water spray. Experimental results demonstrate enhanced aerosol removal via aerosol-mist agglomeration, with charged mist significantly improving particle capture by increasing wettability and size. The average improvements for stainless steel, carbon steel, and concrete were 40%, 44%, and 21%, respectively. The results of experiments using charged mist with different polarities (both positive and negative) and different surface coatings reveal that the dominant polarity of aerosols varies with the irradiated materials, influenced by their crystal structure and electron emission properties. Notably, surface coatings such as ZrO$$_2$$ and CeO$$_2$$ were found to possibly alter aerosol charging characteristics, thereby affecting aerosol removal efficiency with charged mist configurations. The innovative aerosol-mist agglomeration approach shows promise in mitigating radiation exposure, ensuring environmental safety, and reducing contaminated water during reactor dismantling. This study contributes critical knowledge for the development of advanced aerosol management strategies for nuclear reactor decommissioning. The understanding obtained in this work is also expected to be useful for various environmental and chemical engineering applications such as gas decontamination, air purification, and pollution control.

論文

Investigating eutectic behavior and material relocation in B$$_{4}$$C-stainless steel composites using the improved MPS method

Ahmed, Z.*; Wu, S.*; Sharma, A.*; Kumar, R.*; 山野 秀将; Pellegrini, M.*; 横山 諒*; 岡本 孝司*

International Journal of Heat and Mass Transfer, 250, p.127343_1 - 127343_17, 2025/11

https://doi.org/10.1016/j.ijheatmasstransfer.2025.127343
 被引用回数：5 パーセンタイル：72.82(Thermodynamics)

The study aims to measure boron concentration through the unidirectional diffusion of boron within the stainless steel (SS) layers while evaluating the updated model ability to replicate melt relocation behavior and geometry. In the current MPS simulations, one scenario employed dummy walls as heat sources, while another scenario used SS surface particles as heat sources to avoid interference with the melt flow as it reached the bottom of the specimen.

論文

Unveiling the local effects of PTL passivation in PEM Electrolyzers through gas and current mapping using operando neutron radiography and polarized neutron imaging

Karimi, V.*; Qvistgaard, C. H.*; Schmidt, S.*; Wolfertz, A.*; Parker, J. D.*; 甲斐 哲也; 林田 洋寿*; 篠原 武尚; Angelis, S. D.*; Tengattini, A.*; et al.

ACS Applied Materials & Interfaces, 17(36), p.50742 - 50752, 2025/08

https://doi.org/10.1021/acsami.5c11706
 被引用回数：9 パーセンタイル：79.52(Nanoscience & Nanotechnology)

Anodic Ti-based porous transport layers (PTLs) are paramount for advancing high-efficiency proton exchange membrane water electrolyzers (PEMWEs). One of the major challenges with the development of PEMWE is the PTL/catalyst layer interface passivation, which is commonly alleviated by coating precious metals such as Pt. Herein, we report, for the first time, the usage of polarized neutron imaging (PNI) on a half-half PTL approach to investigate current distribution inside the PTL layer under the influence of Ti passivation under PEMWE operando condition. First, the electrochemical study of PEMWE reveals an obvious advantage of Pt coating in preventing Ti passivation by showing 822 mV less overpotential at 1 A cm$$^{-2}$$ (1.771 V) for the superior sample (Pt-coated PTL) compared to the PEMWE with pristine Ti PTL (2.539 V). Second, it is confirmed that using ex situ electronic and structural characterizations, Ti passivation cannot be recognized, suggesting a temporary passivation process in an operating PEMWE. Employing PNI for operando mapping of the current distribution inside the PEMWE shows that most of the electrical current favors the Pt-coated PTL, perfectly aligned with the results obtained from the high-resolution operando neutron radiography in which around 60% of the produced oxygen was found in the Pt-coated PTL.

論文

Magnetism of kagome metals (Fe$$_{1-x}$$Co$$_x$$)Sn studied by $$mu$$SR

Cai, Y.*; Yoon, S.*; Sheng, Q.*; Zhao, G.*; Seewald, E. F.*; Ghosh, S.*; Ingham, J.*; Pasupathy, A. N.*; Queiroz, R.*; Lei, H.*; et al.

Physical Review B, 111(21), p.214412_1 - 214412_17, 2025/06

https://doi.org/10.1103/PhysRevB.111.214412
 被引用回数：3 パーセンタイル：40.34(Materials Science, Multidisciplinary)

We study the magnetic properties of the metallic kagome system (Fe$$_{1-x}$$Co$$_x$$)Sn by a combination of muon spin relaxation ($$mu$$SR), magnetic susceptibility, and scanning tunneling microscopy (STM) measurements in single crystal specimens with Co concentrations $$x$$ = 0, 0.11, 0.8. In the undoped antiferromagnetic compound FeSn, we find possible signatures for a previously unidentified phase that sets in at $$T^{*}sim 50$$~K, well beneath the Neel temperature $$T_{N}sim 376$$~K as indicated by a peak in the relaxation rate 1/$$T_1$$ observed in zero field (ZF) and longitudinal field (LF) $$mu$$SR measurements, with a corresponding anomaly in the ac and dc susceptibility, and an increase in the static width 1/$$T_2$$ in ZF-$$mu$$SR measurements. No signatures of spatial symmetry breaking are found in STM down to 7~K. Related to the location and motion of muons in FeSn, we confirmed a previous report that about 40% of the implanted muons reside at a field-cancelling high symmetry site at $$T < 250$$~K, while an onset of thermal hopping changes the site occupancy at higher temperatures. In Fe$$_{0.89}$$Co$$_{0.11}$$Sn, where disorder eliminated the field-cancellation effect, all the implanted muons exhibit precession and/or relaxation in the ordered state. In Fe$$_{0.2}$$Co$$_{0.8}$$Sn, we find canonical spin glass behavior with freezing temperature $$T_gsim 3.5$$~K; the ZF and LF-$$mu$$SR time spectra exhibit results similar to those observed in dilute alloy spin glasses CuMn and AuFe, with a critical behavior of $$1/T_1$$ at $$T_g$$ and $$1/T_1to 0$$ as $$Tto 0$$. The absence of spin dynamics at low temperatures makes a clear contrast to the spin dynamics observed by $$mu$$SR in many geometrically frustrated spin systems on insulating kagome, pyrochlore, and triangular lattices. The spin glass behavior of CoSn doped with dilute Fe moments is shown to originate primarily from the randomness of doped Fe moments rather than due to geometrical frustration of the underlying lattice.

論文

Investigation of aerosol generation through laser cleaning of various surfaces and optimization of mist & spray scavenging

Sharma, A. K.*; Xu, R.*; Ahmed, Z.*; 三輪 修一郎*; 鈴木 俊一*; 小菅 淳

Journal of Aerosol Science, 177, p.106329_1 - 106329_21, 2024/03

https://doi.org/10.1016/j.jaerosci.2023.106329
 被引用回数：25 パーセンタイル：93.66(Engineering, Chemical)

To ensure the safe and effective decommissioning of the Fukushima Daiichi Nuclear Power Plant (NPP), it is crucial to investigate the behavior of radioactive aerosols generated during the laser decontamination of radiation hot spots and laser cutting of fuel debris. Understanding the generation and dispersion patterns of these aerosols is of utmost importance for the proper planning and execution of decommissioning activities. This study focuses on the performance evaluation of high-power continuous wave (CW) fiber lasers for cleaning surfaces composed of carbon steel, stainless steel, and concrete. The effective confinement and scavenging of radioactive aerosols are critical in minimizing the risk of radiation exposure during decommissioning processes. Test samples, made of carbon steel (CS), stainless steel (SS), and concrete, coated with ZrO$$_{2}$$, CeO$$_{2}$$, and CsI, were subjected to laser decontamination using a class-4 fiber laser within the UTARTS (University of Tokyo Aerosol Removal Test with Sprays) facility. The aerosol particles generated during the laser decontamination process were confined and captured utilizing a spray and mist system. The study proposes the utilization of a combined spray and mist technique, which has demonstrated high efficiency in scavenging aerosols generated through laser irradiation. This research contributes to the broader goal of promoting best practices and innovative solutions in the field of nuclear decommissioning, thereby safeguarding the environment and human health.

論文

Quantum critical spin-liquid-like behavior in the $$S$$ = $$frac{1}{2}$$ quasikagome-lattice compound CeRh$$_{1-x}$$Pd$$_x$$Sn investigated using muon spin relaxation and neutron scattering

Tripathi, R.*; Adroja, D. T.*; Ritter, C.*; Sharma, S.*; Yang, C.*; Hillier, A. D.*; Koza, M. M.*; Demmel, F.*; Sundaresan, A.*; Langridge, S.*; et al.

Physical Review B, 106(6), p.064436_1 - 064436_17, 2022/08

https://doi.org/10.1103/PhysRevB.106.064436
 被引用回数：13 パーセンタイル：61.83(Materials Science, Multidisciplinary)

We present the results of muon spin relaxation ($$mu$$SR) and neutron scattering measurements on the Ce-based quasikagome lattice CeRh$$_{1-x}$$Pd$$_x$$Sn ($$x$$ = 0.1 to 0.75). Our $$mu$$SR results reveal the absence of both static long-range magnetic order and spin freezing down to 0.05 K in the $$x$$ = 0.1 sample, which is consistent with neutron scattering results. The weak temperature-dependent plateaus of the dynamic spin fluctuations below 0.2 K in zero field together with its longitudinal-field (LF) dependence indicate the presence of dynamic spin fluctuations persisting even at 0.05 K without static magnetic order. We argue that such a behavior for $$x$$ = 0.1 can be attributed to a metallic spin-liquid-like ground state near the quantum critical point in the frustrated Kondo lattice. The LF-$$mu$$SR study suggests that the out of kagome plane spin fluctuations are responsible for the spin-liquid behavior.

論文

Event structure and double helicity asymmetry in jet production from polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07

https://doi.org/10.1103/PhysRevD.84.012006
 被引用回数：36 パーセンタイル：75.17(Astronomy & Astrophysics)

重心エネルギー200GeVでの縦偏極陽子陽子衝突からのジェット生成のイベント構造と二重非対称($$A_{LL}$$)について報告する。光子と荷電粒子がPHENIX実験で測定され、イベント構造がPHYTIAイベント生成コードの結果と比較された。再構成されたジェットの生成率は2次までの摂動QCDの計算で十分再現される。測定された$$A_{LL}$$は、一番低い横運動量で-0.0014$$pm$$0.0037、一番高い横運動量で-0.0181$$pm$$0.0282であった。この$$A_{LL}$$の結果を幾つかの$$Delta G(x)$$の分布を仮定した理論予想と比較する。

論文

Identified charged hadron production in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; 秋葉 康之*; Al-Bataineh, H.*; Alexander, J.*; 青木 和也*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

https://doi.org/10.1103/PhysRevC.83.064903
 被引用回数：200 パーセンタイル：99.33(Physics, Nuclear)

200GeVと62.4GeVでの陽子陽子の中心衝突からの$$pi, K, p$$の横運動量分布及び収量をRHICのPHENIX実験によって測定した。それぞれエネルギーでの逆スロープパラメーター、平均横運動量及び単位rapidityあたりの収量を求め、異なるエネルギーでの他の測定結果と比較する。また$$m_T$$や$$x_T$$スケーリングのようなスケーリングについて示して陽子陽子衝突における粒子生成メカニズムについて議論する。さらに測定したスペクトルを二次の摂動QCDの計算と比較する。

論文

Azimuthal correlations of electrons from heavy-flavor decay with hadrons in $$p+p$$ and Au+Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; 秋葉 康之*; Al-Bataineh, H.*; Alexander, J.*; 青木 和也*; Aphecetche, L.*; Aramaki, Y.*; et al.

Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04

https://doi.org/10.1103/PhysRevC.83.044912
 被引用回数：10 パーセンタイル：53.41(Physics, Nuclear)

重いフレーバーのメソンの崩壊からの電子の測定は、このメソンの収量が金金衝突では陽子陽子に比べて抑制されていることを示している。われわれはこの研究をさらに進めて二つの粒子の相関、つまり重いフレーバーメソンの崩壊からの電子と、もう一つの重いフレーバーメソンあるいはジェットの破片からの荷電ハドロン、の相関を調べた。この測定は重いクォークとクォークグルオン物質の相互作用についてのより詳しい情報を与えるものである。われわれは特に金金衝突では陽子陽子に比べて反対側のジェットの形と収量が変化していることを見いだした。

論文

Measurement of neutral mesons in $$p$$ + $$p$$ collisions at $$sqrt{s}$$ = 200 GeV and scaling properties of hadron production

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03

https://doi.org/10.1103/PhysRevD.83.052004
 被引用回数：190 パーセンタイル：98.22(Astronomy & Astrophysics)

RHIC-PHENIX実験で重心エネルギー200GeVの陽子陽子衝突からの$$K^0_s$$, $$omega$$, $$eta'$$と$$phi$$中間子生成の微分断面積を測定した。これらハドロンの横運動量分布のスペクトルの形はたった二つのパラメーター、$$n, T$$、のTsallis分布関数でよく記述できる。これらのパラメーターはそれぞれ高い横運動量と低い横運動量の領域のスペクトルを決めている。これらの分布をフィットして得られた積分された不変断面積はこれまで測定されたデータ及び統計モデルの予言と一致している。

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