To prolong the service lifetime of hot-section components used in marine environment at elevated tem-peratures,it is crucial to explore and develop high-temperature corrosion-resistant coatings.High-velocity oxygen fu...To prolong the service lifetime of hot-section components used in marine environment at elevated tem-peratures,it is crucial to explore and develop high-temperature corrosion-resistant coatings.High-velocity oxygen fuel(HVOF)sprayed NiCoCrAlY,Pt-modified NiCoCrAlY and pre-oxidized Pt-modified NiCoCrAlY coatings were prepared and investigated.This study is concerned with the performance of three coat-ings in a simulated marine environment based on the phase composition of corrosion products and mi-crostructure evolution of coating samples combined with first-principles density functional theory.The results show that the NiCoCrAlY coating was subject to accelerated corrosion and extensive aluminum depletion,leading to premature coating failure.The high-temperature corrosion resistance of Pt-modified NiCoCrAlY coating was found to be better than that of NiCoCrAlY coating.In contrast,the pre-oxidized Pt-modified NiCoCrAlY coating offered long-lasting protection and exhibited the best corrosion resistance,which is attributed to the positive synergistic effect between Pt modification and pre-oxidation.展开更多
In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar ...In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar collision species alternated frequently between 9644 Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr.In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data,STAR developed a three-step blind analysis procedure.Analysts are initially provided a"reference sample"of data,comprised of a mix of events from the two species,the order of which respects time-dependent changes in run conditions.After tuning analysis codes and performing time-dependent quality assurance on the reference sample,analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual≈30-min data-taking runs.For this sample,species-specific information is disguised,but individual output files contain data from a single isobar species.Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage.Following these modifications,the"frozen"code is passed over the fully un-blind data,completing the blind analysis.As a check of the feasibility of the blind analysis procedure,analysts completed a"mock data challenge,"analyzing data from Au+Au collisions at√^(S)NN=27 Ge V,collected in 2018.The Au+Au data were prepared in the same manner intended for the isobar blind data.The details of the blind analysis procedure and results from the mock data challenge are presented.展开更多
Laser surface melting (LSM) was applied on a cast Ni–Al bronze (NAB), which was a crucial material for marine ship propellers. A 720 μm-thick LSM layer with fine equiaxed and dendritic microstructures was obtained. ...Laser surface melting (LSM) was applied on a cast Ni–Al bronze (NAB), which was a crucial material for marine ship propellers. A 720 μm-thick LSM layer with fine equiaxed and dendritic microstructures was obtained. After immersion for 30 days, the corrosion rate of cast NAB was reduced by 25% after LSM. Preferential corrosion occurred and deep corrosion pits appeared at α + κIII microstructure for the cast NAB. LSM NAB underwent general corrosion, and a much more protective film formed on the surface because of the homogenized microstructure. The mass loss of the cast NAB was approximately 2.1 times larger than that of LSM NAB after cavitation erosion (CE) in 3.5 wt.% NaCl solution for 5 h. For the two materials, the mechanical impact effect was dominantly responsible for CE damage. Therefore, the improved hardness and homogenized microstructure contributed to the improved CE resistance of LSM NAB. CE destructed the film, shifted the open circuit potential toward a more negative value, and raised the current density by an order of magnitude. Corrosion at the cast eutectoid microstructure and the dendrites of LSM NAB facilitates the degradation under the cavitation attack. CE-corrosion synergy was largely caused by corrosion-enhanced-CE.展开更多
Dihadron azimuthal correlations containing a high transverse momentum(pr)trigger particle are sensit-ive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the tr...Dihadron azimuthal correlations containing a high transverse momentum(pr)trigger particle are sensit-ive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium,ie.jet-quenching.Previous measurements revealed a strong modification to di-hadron azimuthal correlations in Au+Au collisions with respect to ptp and d+Au collisions.The modification in-creases with the collision centrality,suggesting a path-length or energy density dependence to the je-quenching ef-fect.This paper reports STAR measurements of dihadron azimuthal correlations in mid-central(20%-60%)Au+Au collisions at√^(S)NN=200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane,Ф_(s)=|Ф_(t)-ψ_(Ep)|.The azimuthal correlation is studied as a function of both the trigger and associated particle pr.The subtractions of the combinatorial background and anisotropic flow,assuming Zero Yield At Minimum(ZYAM),are described.The correlation results are first discussed with subtraction of the even harmonic(elliptic and quadrangu-lar)flow backgrounds.The away-side correlation is strongly modifed,and the modification varies withФ_(s),with a double-peak structure for out-of-plane trigger particles.The near-side ridge(long range pseudo-rapidity△_(η)correla-tion)appears to drop with increasingФ_(s)while the jet-like component remains approximately constant.The correla-tion functions are further studied with the subtraction of odd harmonic triangular flow background arising from fluc-tuations.It is found that the triangular flow,while responsible for the majority of the amplitudes,is not sufficient to explain theφs-dependence of the ridge or the away-side double-peak structure.The dropping ridge withФ_(s)could be attributed to aФ_(s)-dependent lliptie anisotropy;however,the physics mechanism of the ridge remains an open ques-tion.Even with aФ_(s)-dependent elliptic flow,the away-side correlation structure is robust.These results,with extens-ive systematic studies of the dihadron correlations as a function ofФ_(s),trigger and associated particle pT,and the pseudo-rapidity range△_(η),should provide stringent inputs to help understand the underlying physics mechanisms of jet-medium interactions in high energy nuclear collisions.展开更多
High transverse momentum(pT)particle production is suppressed owing to the parton(jet)energy loss in the hot dense medium created in relativistic heavy-ion collisions.Redistribution of energy at low-to-modest pT has b...High transverse momentum(pT)particle production is suppressed owing to the parton(jet)energy loss in the hot dense medium created in relativistic heavy-ion collisions.Redistribution of energy at low-to-modest pT has been difficult to measure,owing to large anisotropic backgrounds.We report a data-driven method for background evaluation and subtraction,exploiting the away-side pseudorapidity gaps,to measure the jetlike correlation shape in Au+Au collisions at √sNN=200 GeV in the STAR experiment.The correlation shapes,for trigger particles pT>3GeV/c and various associated particle pT ranges within 0.5<pT<10GeV/c,are consistent with Gaussians,and their widths increase with centrality.The results indicate jet broadening in the medium created in central heavy-ion collisions.展开更多
The interaction of relativistically intense lasers with opaque targets represents a highly non-linear,multi-dimensional parameter space.This limits the utility of sequential 1D scanning of experimental parameters for ...The interaction of relativistically intense lasers with opaque targets represents a highly non-linear,multi-dimensional parameter space.This limits the utility of sequential 1D scanning of experimental parameters for the optimization of secondary radiation,although to-date this has been the accepted methodology due to low data acquisition rates.High repetition-rate(HRR)lasers augmented by machine learning present a valuable opportunity for efficient source optimization.Here,an automated,HRR-compatible system produced high-fidelity parameter scans,revealing the influence of laser intensity on target pre-heating and proton generation.A closed-loop Bayesian optimization of maximum proton energy,through control of the laser wavefront and target position,produced proton beams with equivalent maximum energy to manually optimized laser pulses but using only 60%of the laser energy.This demonstration of automated optimization of laser-driven proton beams is a crucial step towards deeper physical insight and the construction of future radiation sources.展开更多
We present the development and characterization of a high-stability,multi-material,multi-thickness tape-drive target for laser-driven acceleration at repetition rates of up to 100 Hz.The tape surface position was meas...We present the development and characterization of a high-stability,multi-material,multi-thickness tape-drive target for laser-driven acceleration at repetition rates of up to 100 Hz.The tape surface position was measured to be stable on the sub-micrometre scale,compatible with the high-numerical aperture focusing geometries required to achieve relativistic intensity interactions with the pulse energy available in current multi-Hz and near-future higher repetition-rate lasers(>kHz).Long-term drift was characterized at 100 Hz demonstrating suitability for operation over extended periods.The target was continuously operated at up to 5 Hz in a recent experiment for 70,000 shots without intervention by the experimental team,with the exception of tape replacement,producing the largest data-set of relativistically intense laser–solid foil measurements to date.This tape drive provides robust targetry for the generation and study of high-repetitionrate ion beams using next-generation high-power laser systems,also enabling wider applications of laser-driven proton sources.展开更多
The band structure in a kagome lattice can naturally exhibit flat band,Dirac cones,and van Hove singularity,enabling rich interplays between correlation and topology.However,the flat band is rarely detected just at th...The band structure in a kagome lattice can naturally exhibit flat band,Dirac cones,and van Hove singularity,enabling rich interplays between correlation and topology.However,the flat band is rarely detected just at the Fermi level in kagome materials,which would be crucial to realize emergent flat band physics.Here,combining angle-resolved photoemission spectroscopy,transport measurements and first-principles calculation,we observe a striking Fermi-level flat band in paramagnetic YCr_(6)Ge_(6)as a typical signature of electronic kagome lattice.We explicitly unveil that orbital character plays an essential role to realize electronic kagome lattice in crystals with transition-metal kagome layers.We further engineer this material with magnetic rare earth elements to break the time-reversal symmetry of the Fermi-level kagome flat band.Our work establishes a Fermi-level flat band in a kagome magnet as an exciting quantum platform.展开更多
基金supported by the National Science and Technology Major Project(No.J2019-IV-0006-0074)the Key Research Program of the Chinese Academy of Sciences(No.ZDRW-CN-2021-2-2)+2 种基金the National Natural Science Foundation of China(No.52301116)support by the Joint Funds of the National Natural Science Foundation of China(“Ye Qisun”Science Funds,No.U2241251)the Innovation Engineering Project(No.211-XXXX-N106-01).
文摘To prolong the service lifetime of hot-section components used in marine environment at elevated tem-peratures,it is crucial to explore and develop high-temperature corrosion-resistant coatings.High-velocity oxygen fuel(HVOF)sprayed NiCoCrAlY,Pt-modified NiCoCrAlY and pre-oxidized Pt-modified NiCoCrAlY coatings were prepared and investigated.This study is concerned with the performance of three coat-ings in a simulated marine environment based on the phase composition of corrosion products and mi-crostructure evolution of coating samples combined with first-principles density functional theory.The results show that the NiCoCrAlY coating was subject to accelerated corrosion and extensive aluminum depletion,leading to premature coating failure.The high-temperature corrosion resistance of Pt-modified NiCoCrAlY coating was found to be better than that of NiCoCrAlY coating.In contrast,the pre-oxidized Pt-modified NiCoCrAlY coating offered long-lasting protection and exhibited the best corrosion resistance,which is attributed to the positive synergistic effect between Pt modification and pre-oxidation.
文摘In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar collision species alternated frequently between 9644 Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr.In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data,STAR developed a three-step blind analysis procedure.Analysts are initially provided a"reference sample"of data,comprised of a mix of events from the two species,the order of which respects time-dependent changes in run conditions.After tuning analysis codes and performing time-dependent quality assurance on the reference sample,analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual≈30-min data-taking runs.For this sample,species-specific information is disguised,but individual output files contain data from a single isobar species.Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage.Following these modifications,the"frozen"code is passed over the fully un-blind data,completing the blind analysis.As a check of the feasibility of the blind analysis procedure,analysts completed a"mock data challenge,"analyzing data from Au+Au collisions at√^(S)NN=27 Ge V,collected in 2018.The Au+Au data were prepared in the same manner intended for the isobar blind data.The details of the blind analysis procedure and results from the mock data challenge are presented.
基金This research was financially supported by Fundamental Research Funds for the Central Universities of P.R.China(Nos.B210203049,B210204005 and B210203049)Natural Science Foundation of Jiangsu Province(Nos.BK20191161 and BK 20180984)National Natural Science Foundation of China(Nos.51601058,51879089 and 52005228).
文摘Laser surface melting (LSM) was applied on a cast Ni–Al bronze (NAB), which was a crucial material for marine ship propellers. A 720 μm-thick LSM layer with fine equiaxed and dendritic microstructures was obtained. After immersion for 30 days, the corrosion rate of cast NAB was reduced by 25% after LSM. Preferential corrosion occurred and deep corrosion pits appeared at α + κIII microstructure for the cast NAB. LSM NAB underwent general corrosion, and a much more protective film formed on the surface because of the homogenized microstructure. The mass loss of the cast NAB was approximately 2.1 times larger than that of LSM NAB after cavitation erosion (CE) in 3.5 wt.% NaCl solution for 5 h. For the two materials, the mechanical impact effect was dominantly responsible for CE damage. Therefore, the improved hardness and homogenized microstructure contributed to the improved CE resistance of LSM NAB. CE destructed the film, shifted the open circuit potential toward a more negative value, and raised the current density by an order of magnitude. Corrosion at the cast eutectoid microstructure and the dendrites of LSM NAB facilitates the degradation under the cavitation attack. CE-corrosion synergy was largely caused by corrosion-enhanced-CE.
基金Supported in part by the Offices of NP and HEP within the U.S.DOE Office of Sciencethe U.S.NSF+18 种基金the Sloan Foundationthe DFG cluster of excellence‘Origin and Structure of the Universe’of Germany,CNRS/IN2P3STFC and EPSRC of the United KingdomFAPESP CNPq of Brazil,Ministry of Ed.Sci.of the Russian FederationNNSFCCASMoSTMoE of ChinaGA and MSMT of the Czech RepublicFOM and NWO of the NetherlandsDAEDSTCSIR of IndiaPolish Ministry of Sci.Higher Ed.,Korea Research Foundation,Ministry of Sci.,Ed.Sports of the Rep.Of CroatiaRussian Ministry of Sci.and TechRos-Atom of Russia。
文摘Dihadron azimuthal correlations containing a high transverse momentum(pr)trigger particle are sensit-ive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium,ie.jet-quenching.Previous measurements revealed a strong modification to di-hadron azimuthal correlations in Au+Au collisions with respect to ptp and d+Au collisions.The modification in-creases with the collision centrality,suggesting a path-length or energy density dependence to the je-quenching ef-fect.This paper reports STAR measurements of dihadron azimuthal correlations in mid-central(20%-60%)Au+Au collisions at√^(S)NN=200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane,Ф_(s)=|Ф_(t)-ψ_(Ep)|.The azimuthal correlation is studied as a function of both the trigger and associated particle pr.The subtractions of the combinatorial background and anisotropic flow,assuming Zero Yield At Minimum(ZYAM),are described.The correlation results are first discussed with subtraction of the even harmonic(elliptic and quadrangu-lar)flow backgrounds.The away-side correlation is strongly modifed,and the modification varies withФ_(s),with a double-peak structure for out-of-plane trigger particles.The near-side ridge(long range pseudo-rapidity△_(η)correla-tion)appears to drop with increasingФ_(s)while the jet-like component remains approximately constant.The correla-tion functions are further studied with the subtraction of odd harmonic triangular flow background arising from fluc-tuations.It is found that the triangular flow,while responsible for the majority of the amplitudes,is not sufficient to explain theφs-dependence of the ridge or the away-side double-peak structure.The dropping ridge withФ_(s)could be attributed to aФ_(s)-dependent lliptie anisotropy;however,the physics mechanism of the ridge remains an open ques-tion.Even with aФ_(s)-dependent elliptic flow,the away-side correlation structure is robust.These results,with extens-ive systematic studies of the dihadron correlations as a function ofФ_(s),trigger and associated particle pT,and the pseudo-rapidity range△_(η),should provide stringent inputs to help understand the underlying physics mechanisms of jet-medium interactions in high energy nuclear collisions.
文摘High transverse momentum(pT)particle production is suppressed owing to the parton(jet)energy loss in the hot dense medium created in relativistic heavy-ion collisions.Redistribution of energy at low-to-modest pT has been difficult to measure,owing to large anisotropic backgrounds.We report a data-driven method for background evaluation and subtraction,exploiting the away-side pseudorapidity gaps,to measure the jetlike correlation shape in Au+Au collisions at √sNN=200 GeV in the STAR experiment.The correlation shapes,for trigger particles pT>3GeV/c and various associated particle pT ranges within 0.5<pT<10GeV/c,are consistent with Gaussians,and their widths increase with centrality.The results indicate jet broadening in the medium created in central heavy-ion collisions.
基金support from the UK STFC grants ST/V001639/1 with the XFEL Physical Sciences Hub and ST/P002021/1the UK EPSRC grants EP/V049577/1 and EP/R006202/1+5 种基金as well as the U.S.DOE Office of Science,Fusion Energy Sciences under FWP No.100182in part by the National Science Foundation under Grant No.1632708 and Award No.PHY–1903414M.J.V.S.acknowledges support from the Royal Society URFR1221874support from the DOE NNSA SSGF program under DE-NA0003960support from the U.S.DOE grant DESC0016804support from the project‘Advanced research using high-intensity laser-produced photons and particles’(CZ.02.1.01/0.0/0.0/16_019/0000789)from the European Regional Development Fund(ADONIS)。
文摘The interaction of relativistically intense lasers with opaque targets represents a highly non-linear,multi-dimensional parameter space.This limits the utility of sequential 1D scanning of experimental parameters for the optimization of secondary radiation,although to-date this has been the accepted methodology due to low data acquisition rates.High repetition-rate(HRR)lasers augmented by machine learning present a valuable opportunity for efficient source optimization.Here,an automated,HRR-compatible system produced high-fidelity parameter scans,revealing the influence of laser intensity on target pre-heating and proton generation.A closed-loop Bayesian optimization of maximum proton energy,through control of the laser wavefront and target position,produced proton beams with equivalent maximum energy to manually optimized laser pulses but using only 60%of the laser energy.This demonstration of automated optimization of laser-driven proton beams is a crucial step towards deeper physical insight and the construction of future radiation sources.
基金Special thanks go to the staff at the Central Laser Facility who provided laser operational support,mechanical and electrical support and computational and administrative support throughout the experiment.We acknowledge funding from UK STFC,Grant Nos.ST/P002021/1 and ST/V001639/1U.S.DOE Office of Science,Fusion Energy Sciences under FWP No.100182+2 种基金in part by the National Science Foundation under Grant No.1632708G.D.G.acknowledges support from the DOE NNSA SSGF program under DE-NA0003960This work has been partially supported by the project Advanced Research Using High-intensity Laser-produced Photons and Particles(CZ.02.1.01/0.0/0.0/16_019/0000789)from the European Regional Development Fund(ADONIS).
文摘We present the development and characterization of a high-stability,multi-material,multi-thickness tape-drive target for laser-driven acceleration at repetition rates of up to 100 Hz.The tape surface position was measured to be stable on the sub-micrometre scale,compatible with the high-numerical aperture focusing geometries required to achieve relativistic intensity interactions with the pulse energy available in current multi-Hz and near-future higher repetition-rate lasers(>kHz).Long-term drift was characterized at 100 Hz demonstrating suitability for operation over extended periods.The target was continuously operated at up to 5 Hz in a recent experiment for 70,000 shots without intervention by the experimental team,with the exception of tape replacement,producing the largest data-set of relativistically intense laser–solid foil measurements to date.This tape drive provides robust targetry for the generation and study of high-repetitionrate ion beams using next-generation high-power laser systems,also enabling wider applications of laser-driven proton sources.
基金supported by the Ministry of Science and Technology of China(Grants No.2018YFA0307000,and No.2018FYA0305800)the Innovation Program for Quantum Science and Technology(No.2021ZD0302802)+1 种基金the National Natural Science Foundation of China(Grants No.U2032128,and No.11874047)the Fundamental Research Funds for the Central Universities(Grant No.2042021kf0210).
文摘The band structure in a kagome lattice can naturally exhibit flat band,Dirac cones,and van Hove singularity,enabling rich interplays between correlation and topology.However,the flat band is rarely detected just at the Fermi level in kagome materials,which would be crucial to realize emergent flat band physics.Here,combining angle-resolved photoemission spectroscopy,transport measurements and first-principles calculation,we observe a striking Fermi-level flat band in paramagnetic YCr_(6)Ge_(6)as a typical signature of electronic kagome lattice.We explicitly unveil that orbital character plays an essential role to realize electronic kagome lattice in crystals with transition-metal kagome layers.We further engineer this material with magnetic rare earth elements to break the time-reversal symmetry of the Fermi-level kagome flat band.Our work establishes a Fermi-level flat band in a kagome magnet as an exciting quantum platform.
