Efficient guiding and focusing of intense laser pulse using periodic thin slits

Slits have been widely used in laser-plasma interactions as plasma optical components for generating high-harmonic light and controlling laser-driven particle beams.Here,we propose and demonstrate that periodic thin slits can be regarded as a new breed of optical elements for efficient focusing and guiding of intense laser pulse.The fundamental physics of intense laser interaction with thin slits is studied,and it is revealed that relativistic effects can lead to enhanced laser focusing far beyond the pure diffractive focusing regime.In addition,the interaction of an intense laser pulse with periodic thin slits makes it feasible to achieve multifold enhancement in both laser intensity and energy transfer efficiency compared with conventional waveguides.These results provide a novel method for manipulating ultra-intense laser pulses and should be of interest for many laser-based applications.

铥原子收敛于4f^(13)(~2F~?_(7/2))6s(7/2,1/2)~?_4和4f^(13)(~2F~?7/2)6s(7/2,1/2)~?_3偶宇称里德伯系列能级的电子关联效应

本文在多通道量子亏损理论框架下,利用相对论多通道理论,计算了铥原子收敛于4f^(13)(~2F?_(7/2))6s(7/2,1/2)?_4和4f^(13)(~2F?7/2)6s(7/2,1/2)?_3的三个偶宇称里德伯系列.通过将计算结果与美国国家标准与技术研究院数据进行比较,展示了两种类型的电子关联效应:1)里德伯系列之间的相互作用,导致里德伯系列的能级出现整体偏移; 2)一个孤立的干扰态镶嵌在一个里德伯系列中,破坏了该里德伯系列能级的规则性.

Double heterogeneous structures induced excellent strength-ductility synergy in Ni_(40)Co_(30)Cr_(20)Al_(5)Ti_(5)medium-entropy alloy

The application of single-phase face-centered cubic(FCC)medium entropy alloys(MEAs)in the engi-neering industry is often hindered by the challenge of insufficient strength.In this study,a novel non-equiatomic ratio Ni_(40)Co_(30)Cr_(20)Al_(5)Ti_(5)MEA was successfully fabricated.Through the well-designed mechan-ical heat treatment processing,we introduced a heterogeneous grain structure comprising 67.4%fine grain and 32.6%coarse grain.Additionally,heterogeneous size L12 phases consisting of 18.7%submicron precip-itates and 11.7%nano-sized precipitates,were incorporated into the alloy.Tensile tests conducted at room temperature revealed that the double heterogeneous structure alloy demonstrated remarkable strength–ductility synergy.It exhibited a yield strength of 1200 MPa,an ultimate tensile strength of 1560 MPa and a total elongation of 33.6%.The exceptional strength of the alloy can be primarily attributed to heteroge-neous deformation induced strengthening,grain boundary strengthening and precipitation strengthening.The excellent ductility is mainly attributed to the high-density stacking faults and Lomer–Cottrell locks.This study not only contributes to the clarification of the strengthening and deformation mechanism of double heterogeneous structure alloys but also provides an effective strategy for the development of high-performance alloys with high strength and ductility.

Amplitude analysis of the decays D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)

Using e^(+)e^(−)annihilation data corresponding to an integrated luminosity of 2.93 fb^(−1)taken at the center-of-mass energy√s=3.773 GeV with the BESIII detector,a joint amplitude analysis is performed on the decays D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η).The fit fractions of individual components are obtained,and large interferences among the dominant components of the decays D^(0)→a_(1)(1260)π,D^(0)→π(1300)π,D^(0)→ρ(770)ρ(770),and D^(0)→2(ππ)_(S)are observed in both channels.With the obtained amplitude model,the CP-even fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are determined to be(75.2±1.1_(stat).±1.5_(syst.))%and(68.9±1.5_(stat).±2.4_(syst.))%,respectively.The branching fractions of D^(0)→π^(+)π^(−)π^(+)π^(−)and D^(0)→π^(+)π^(−)π^(0)π^(0)(non-η)are measured to be(0.688±0.010_(stat.)±0.010_(syst.))%and(0.951±0.025_(stat.)±0.021_(syst.))%,respectively.The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters of D^(0)→4πwhen used to determine the CKM angleγ(ϕ_(3))via the B^(−)→DK^(−)decay.

Determination of the number ofψ(3686)events taken at BESⅢ

The number ofψ(3686)events collected by the BESⅢdetector during the 2021 run period is determined to be(2259.3±11.1)×10~6 by counting inclusiveψ(3686)hadronic events.The uncertainty is systematic and the statistical uncertainty is negligible.Meanwhile,the numbers ofψ(3686)events collected during the 2009 and 2012run periods are updated to be(107.7±0.6)×10~6 and(345.4±2.6)×10~6,respectively.Both numbers are consistent with the previous measurements within one standard deviation.The total number ofψ(3686)events in the three data samples is(2712.4±14.3)×10~6.

Excellent strength-ductility combination in Co_(36)Cr_(15)Fe_(18)Ni_(18)Al_(8)Ti_(4)Mo_(1)multi-principal element alloys by dual-morphology B2 precipitates strengthening

Precipitation strengthening provides one of the most widely-used mechanisms for strengthen-ing multi-principal-element alloys(MPEAs).Here,we report dual-morphology B2 precipitates in Co_(36)Cr_(15)Fe_(18)Ni_(18)Al_(8)Ti_(4)Mo_(1)MPEA obtained by thermo-mechanical processing.Electron microscopy charac-terization reveals that the dual-morphology B2 precipitates are either recrystallized B2 particles formed at the grain boundaries or triple junctions with recrystallization process,or rod-like within the non-recrystallized FCC matrix.The dual-morphology B2 precipitates enhance the yield strength and ultimate tensile strength up to 1120 MPa and 1480 MPa,respectively.This work suggests the mechanical proper-ties of the alloy can be optimized by B2 precipitation strengthening to meet the needs of engineering applications.

Three principles for preparing Al wire with high strength and high electrical conductivity

The trade-off relation between the strength and the electrical conductivity has been a Iong-standing dilemma in metallic materials. In the study, three key principles, i.e.elongated grains, sharp texture and nano-scale precipitates, were presented for preparing Al wire with high strength and high electrical conductivity based on the specially designed experiments for breaking the mutually exclusive relation between the strength and the electrical conductivity. The results show that the elongated grains could lead to a higher electrical conductivity in Al wire without sacrificing the strength;while, the <111> sharp texture can efficiently strengthen the Al wire without influencing the electrical conductivity. Furthermore, nano-scale precipitates with proper size can simultaneously improve the strength and electrical conductivity of Al alloy wire. Under the guidance of the above three key principles, Al wires with high strength and high conductivity were prepared.

Investigating the use of an ionic liquid for rare earth mineral flotation

Common collectors for rare earth mineral(REM) flotation,which include carboxylates and hydroxamates,face problems such as being non-selective and sensitive to impurity ions.A type of ionic liquid(IL),tetraethylammonium mono-(2-ethylhexyl)2-ethylhexyl phosphonate([N_(2222)][EHEHP]),has been investigated previously for rare earth elements(REE) solvent extraction,and was proven to be selective and effective.In this work,[N_(2222)][EHEHP] was evaluated as a collector in bastnasite(a primary REM source for REE production) flotation for the first time.The results were compared with quartz and hematite,two common gangue minerals in REM deposits.Zeta potential measurements and Fouriertransform infrared spectroscopy(FT-IR) were completed to investigate the surface chemical properties involved in the flotation of these minerals using this collector.The findings were compared with microflotation results.FT-IR and zeta potential measurements suggest adsorption of the collector’s phosphonate group onto bastnäsite and hematite,likely through chemisorption;whereas for quartz,the minimum micro flotation recovery is likely due to no adsorption of IL on its surface.Micro flotation re sults show higher collectability of [N_(2222)] [EHEHP] for hematite than bastnasite,the latter only shows appreciable recovery at pH 5 with elevated dosage of IL(500 g/t).To achieve better separation,a two-stage flotation scheme was designed and evaluated by bench scale flotation on a synthetic mineral mixture.The concentrates and tails were analyzed by magnetic separation,and it is found that bastnasite recovery over 90% with maximum upgrade ratio 1.7 can be achieved with elevated collector dosage.

Effect of stress profile on microstructure evolution of cold-drawn commercially pure aluminum wire analyzed by finite element simulation

The evolution of microstructure in the drawing process of commercially pure aluminum wire （CPAW） does not only depend on the nature of materials, but also on the stress profile. In this study, the effect of stress profile on the texture evolution of the CPAW was systematically investigated by combining the numerical simulation and the microstructure observation. The results show that the tensile stress at the wire center promotes the formation of 〈111〉 texture, whereas the shear stress nearby the rim makes little contribution to the texture formation. Therefore, the 〈111 〉 texture at the wire center is stronger than that in the surface layer, which also results in a higher microhardness at the center of the CPAW under axial loading.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

Free electron lasers driven by plasma accelerators:status and near-term prospects

Owing to their ultra-high accelerating gradients,combined with injection inside micrometer-scale accelerating wakefield buckets,plasma-based accelerators hold great potential to drive a new generation of free-electron lasers(FELs).Indeed,the first demonstration of plasma-driven FEL gain was reported recently,representing a major milestone for the field.Several groups around the world are pursuing these novel light sources,with methodology varying in the use of wakefield driver(laser-driven or beam-driven),plasma structure,phase-space manipulation,beamline design,and undulator technology,among others.This paper presents our best attempt to provide a comprehensive overview of the global community efforts towards plasma-based FEL research and development.