摘要：Void nucleation and growth under dynamic loading are essential for damage initiation and evolution in ductile metals.In the past few decades,the development of experimental techniques and simulation methods has helped to reveal a wealth of information about the nucleation and growth process from its microscopic aspects to macroscopic ones.Powerful and effective theoretical approaches have been developed based on this information and have helped in the analysis of the damage states of structures,thereby making an important contribution to the design of damageresistant materials.This Review presents a brief overview of theoretical models related to the mechanisms of void nucleation and growth under dynamic loading.Classical work and recent research progress are summarized,together with discussion of some aspects deserving further study.
摘要：Collisionless shocks are ubiquitous in the Universe and are held responsible for the production of nonthermal particles and high-energy radiation.In the absence of particle collisions in the system,theory shows that the interaction of an expanding plasma with a pre-existing electromagnetic structure(as in our case)is able to induce energy dissipation and allow shock formation.Shock formation can alternatively take place when two plasmas interact,through microscopic instabilities inducing electromagnetic fields that are able in turn to mediate energy dissipation and shock formation.Using our platform in which we couple a rapidly expanding plasma induced by high-power lasers(JLF/Titan at LLNL and LULI2000)with high-strength magnetic fields,we have investigated the generation of a magnetized collisionless shock and the associated particle energization.We have characterized the shock as being collisionless and supercritical.We report here on measurements of the plasma density and temperature,the electromagnetic field structures,and the particle energization in the experiments,under various conditions of ambient plasma and magnetic field.We have also modeled the formation of the shocks using macroscopic hydrodynamic simulations and the associated particle acceleration using kinetic particle-in-cell simulations.As a companion paper to Yao et al.[Nat.Phys.17,1177–1182(2021)],here we show additional results of the experiments and simulations,providing more information to allow their reproduction and to demonstrate the robustness of our interpretation of the proton energization mechanism as being shock surfing acceleration.
摘要：A novel bidirectional remotely controlled device for static and dynamic compression/decompression using diamond anvil cells(DACs)has been developed that can control pressure in an accurate and consistent manner.Electromechanical piezoelectric actuators are applied to a conventional DAC,allowing applications under a variety of pressure conditions.Using this static and dynamic DAC(s-dDAC),it is possible to addresses the poorly studied experimental regime lying between purely static and purely dynamic studies.The s-dDAC,driven by three piezoelectric actuators,can be combined with a time-resolved spectral measurement system and high-speed imaging device to study the structural changes,chemical reactions,and properties of materials under extreme conditions.The maximum compression/decompression rate or pressure range highly depends on the culet size of the anvil,and a higher compression rate and wider pressure range can be realized in a DAC with smaller anvil culet.With our s-dDAC,we have been able to achieve the highest compression rate to date with a 300μm culet anvil:48 TPa/s.An overview of a variety of experimental measurements possible with our device is presented.
摘要：We present a Stark–Zeeman spectral line-shape model and the associated numerical code,PPPB,designed to provide fast and accurate line shapes for arbitrary atomic systems for a large range of plasma conditions.PPPB is based on the coupling of the PPP code-a Stark-broadened spectral line-shape code developed for multi-electron ion spectroscopy in hot dense plasmas-and the MASCB code developed recently to generate B-field-dependent atomic physics.The latter provides energy levels,statistical weights,and reduced matrix elements of multi-electron radiators by diagonalizing the atomic Hamiltonian that includes the well know B-dependent term.These are then used as inputs to PPP working in the standard line-broadening approach,i.e.,using the quasi-static ion and impact electron approximations.The effects of ion dynamics are introduced by means of the frequency fluctuation model,and the physical model of electron broadening is based on the semi-classical impact approximation including the effects of a strong collision term,interference,and cyclotron motion.Finally,to account for polarization effects,the output profiles are calculated for a given angle of observation with respect to the direction of the magnetic field.The potential of this model is presented through Stark–Zeeman spectral line-shape calculations performed for various experimental conditions.
摘要：A simultaneous high-resolution x-ray backlighting and self-emission imaging method for laser-produced plasma diagnostics is developed in which two Kirkpatrick–Baez imaging channels for high-energy and low-energy diagnostics are constructed using a combination of multilayer mirrors in near-coaxial form.By using a streak or framing camera placed on the image plane,both backlit and self-emission images of a laserproduced plasma with high spatial and temporal resolution can be obtained simultaneously in a single shot.This paper describes the details of the method with regard to its optical and multilayer design,assembly,and alignment method.In addition,x-ray imaging results with a spatial resolution better than 5μm in the laboratory and experimental results with imploding capsules in the SG-III prototype laser facility are presented.
摘要：I.INTRODUCTION Strong interest in the modeling of planetary interiors,dwarf stars,and the physical conditions necessary to achieve inertial confinement fusion(ICF)have driven attention to the properties of matter at high density,temperature,and pressure(beyond the megabar limit).Extreme states of matter have been studied using gas guns,explosives,and Z-pinches,among other methods(see,e.g.,Refs.1–4).However in recent years,lasers have become the most reliable standard tool for creating extreme states of matter.
摘要：Deep understanding of the impact of photon polarization on pair production is essential for the efficient generation of laser-driven polarized positron beams and demands a complete description of polarization effects in strong-field QED processes.Employing fully polarization-resolved Monte Carlo simulations,we investigate correlated photon and electron(positron)polarization effects in the multiphoton Breit–Wheeler pair production process during the interaction of an ultrarelativistic electron beam with a counterpropagating elliptically polarized laser pulse.We show that the polarization of e−e+pairs is degraded by 35%when the polarization of the intermediate photon is resolved,accompanied by an∼13%decrease in the pair yield.Moreover,in this case,the polarization direction of energetic positrons at small deflection angles can even be reversed when high-energy photons with polarization parallel to the laser electric field are involved.
摘要：We describe the design and x-ray emission properties(temporal,spatial,and spectral)of Dry Pinch I,a portable X-pinch driver developed at Imperial College London.Dry Pinch I is a direct capacitor discharge device,30033003700 mm3 in size and∼50 kg in mass,that can be used as an external driver for x-ray diagnostics in high-energy-density physics experiments.Among key findings,the device is shown to reliably produce 1.1±0.3 ns long x-ray bursts that couple∼50 mJ of energy into photon energies from 1 to 10 keV.The average shot-to-shot jitter of these bursts is found to be 10±4.6 ns using a combination of x-ray and current diagnostics.The spatial extent of the x-ray hot spot from which the radiation emanates agrees with previously published results for X-pinches-suggesting a spot size of 10±6μm in the soft energy region(1–10 keV)and 190±100μm in the hard energy region(>10 keV).These characteristics mean that Dry Pinch I is ideally suited for use as a probe in experiments driven in the laboratory or at external facilities when more conventional sources of probing radiation are not available.At the same time,this is also the first detailed investigation of an X-pinch operating reliably at current rise rates of less than 1 kA/ns.
摘要：Experiments exploring the propagation of heat waves within cylindrical CH foams were performed on the Shenguang-Ⅲ prototype laser facility in 2012.In this paper,the radiation fluxes out of CH foam cylinders at different angles are analyzed theoretically using the two-dimensional radiation hydrodynamics code LARED-R.Owing to the difficulty in validating opacity and equation of state(EOS)data for high-Z plasmas,and to uncertainties in the measured radiation temperature Tr and the original foam densityρ0,multipliers are introduced to adjust the Au material parameters,Tr,andρ0 in our simulations to better explain the measurements.The dependences of the peak radiation flux Fmax and the breakout time of the heat wave thalf(defined as the time corresponding to the radiation flux at half-maximum)on the radiation source,opacity,EOS,andρ0 scaling factors(η_(src),η_(op),η_(eos),and η_(ρ))are investigated via numerical simulations combined with fitting.Then,with the uncertainties in the measured Tr andρ0 fixed at 3.6%and 3.1%,respectively,experimental data are exploited as fiducial values to determine the ranges ofη_(op) andηeos.It is found that the ranges ofη_(op) andηeos fixed by this experiment overlap partially with those found in our previous work[Meng et al.,Phys.Plasmas 20,092704(2013)].Based on the scaled opacity and EOS parameters,the values of F_(max) and t_(half) obtained via simulations are in good agreement with the measurements,with maximum errors∼9.5%and within 100 ps,respectively.
摘要：一、会议背景及主题为推动极端条件下物质与辐射研究领域的国际交流,促进相关领域的学科发展,中国工程物理研究院于2016年创办了英文学术期刊Matter and Radiation at Extremes(MRE)。MRE举办“极端条件下的物质与辐射国际会议(ICMRE)”,旨在为国际相关领域搭建公开、便捷、高水平的学术交流平台,促进先进知识成果的传播与利用。会议自2016年首次召开以来,已先后在四川成都、北京、山东青岛和安徽合肥等地成功举办了四届,吸引了来自十余个国家的千余名学者参与交流。因为疫情原因,第五届“极端条件下的物质与辐射国际会议”延期到2022年举办,由北京应用物理与计算数学研究所和陕西师范大学共同主办。
摘要：Polymeric nitrogen has attracted much attention owing to its possible application as an environmentally safe high-energy-density material.Based on a crystal structure search method accelerated by the use of machine learning and graph theory and on first-principles calculations,we predict a series of metal nitrides with chain-like polynitrogen(P_(21)-AlN_(6),P2_(1)-GaN_(6),P-1-YN_(6),and P_(4)/mnc-TiN_(8)),all of which are estimated to be energetically stable below 40.8 GPa.Phonon calculations and ab initio molecular dynamics simulations at finite temperature suggest that these nitrides are dynamically stable.We find that the nitrogen in these metal nitrides can polymerize into two types of poly-N^(2-)_(4)chains,in which theπelectrons are either extended or localized.Owing to the presence of the polymerized N4 chains,these metal nitrides can store a large amount of chemical energy,which is estimated to range from 4.50 to 2.71 kJ/g.Moreover,these compounds have high detonation pressures and detonation velocities,exceeding those of conventional explosives such as TNT and HMX.
摘要：ABSTRACT Aneutronic fusion reactions such as proton-boron fusion could efficiently produce clean energy with quite low neutron doses.However,as a consequence,conventional neutron spectral methods for diagnosing plasma ion temperature would no longer work.Therefore,finding a way to probe the ion temperature in aneutronic fusion plasmas is a crucial task.Here,we present a method to realize ultrafast in situ probing of^(11)B ion temperature for proton-boron fusion by Doppler broadening of the nuclear resonance fluorescence(NRF)emission spectrum.The NRF emission is excited by a collimated,intenseγ-ray beam generated from submicrometer wires irradiated by a recently available petawatt(PW)laser pulse,where theγ-ray beam generation is calculated by three-dimensional particle-in-cell simulation.When the laser power is higher than 1 PW,five NRF signatures of a^(11)B plasma can be clearly identified with high-resolutionγ-ray detectors,as shown by our Geant4 simulations.The correlation between the NRF peak width and^(11)B ion temperature is discussed,and it is found that NRF emission spectroscopy should be sensitive to 11B ion temperatures T_(i)>2.4 keV.This probing method can also be extended to other neutron-free-fusion isotopes,such as^(6)Li and^(15)N.
摘要：Magnetized laser-produced plasmas are central to many studies in laboratory astrophysics,in inertial confinement fusion,and in industrial applications.Here,we present the results of large-scale three-dimensional magnetohydrodynamic simulations of the dynamics of a laser-produced plasma expanding into a transverse magnetic field with a strength of tens of teslas.The simulations show the plasma being confined by the strong magnetic field into a slender slab structured by the magnetized Rayleigh–Taylor instability that develops at the plasma–vacuum interface.We find that when the initial velocity of the plume is perturbed,the slab can develop kink-like motions that disrupt its propagation.
摘要：A material termed“carbonaceous sulfur hydride”has recently been reported to be a high-pressure room temperature superconductor[Snider et al.,Nature 586,373(2020)].We have previously pointed out that certain anomalies observed in the published data for the ac magnetic susceptibility of this material would be cleared up once the measured raw data were made available[J.E.Hirsch,arXiv:2110.12854v1(2021)and J.E.Hirsch,Physica C 590,1353964(2021)(temporarily removed)].The measured raw data,as well as numerical values of the data presented in figures in the aforementioned paper by Snider et al.,have recently been posted on the arXiv[R.P.Dias and A.Salamat,arXiv:2111.15017v1(2021)and R.P.Dias and A.Salamat,arXiv:2111.15017v2(2021)].Here,we report the results of our analysis of these raw data and published data and our conclusion that the raw data are incompatible with the published data.Implications of these results for the claim that the material is a room temperature superconductor are discussed.
摘要：A practical experimental method is proposed to investigate thermal transport by characterizing the motion of plasma flows through a x-ray spectroscopic technique using tracers.By simultaneously measuring multiple parameters,namely,the mass-ablation rate,the temporal evolution of plasma flow velocities and trajectories and the temperature,it is possible to observe a variety of physical processes,such as shock wave compression,heating by thermal waves,and plasma thermal expansion,and to determine their relative importance in different phases during the irradiation of CH and Au targets.From a comparison with hydrodynamic simulations,we find significant differences in the motion of the plasma flows between CH and Au,which can be attributed to different sensitivities to the thermal transport process.There are also differences in the ablation and electron temperature histories of the two materials.These results confirm that velocities and trajectories of plasma motion can provide useful evidence in the investigation of thermal conduction,and the approach presented here deserves more attention in the context of inertial confinement fusion and high-energy-density physics.
摘要：Synchrotron radiation x-ray diffraction investigations of iron(Fe)and nickel(Ni)are conducted at pressures up to 354 and 368 GPa,respectively,and the equations of state(EOSs)at 298 K for the two elements are obtained for data extending to pressures as high as those at the center of the Earth,using the latest Pt-EOS pressure scale.From a least-squares fit to the Vinet equation using the observed pressure–volume data,the isothermal bulk modulus K0 and its pressure derivative K′0 are estimated to be 159.27(99)GPa and 5.86(4)for hcp-Fe,and 173.5(1.4)GPa and 5.55(5)for Ni.By comparing the present EOSs and extrapolated EOSs reported in the literature for Fe and Ni,the volumes of Fe and Ni at 365 GPa are found to be 2.3%and 1.5%larger than those estimated from extrapolated EOSs in previous studies,respectively.It is concluded that these discrepancies are due to the pressure scale.The present results suggest that the densities of Fe and Ni at a pressure of 365 GPa corresponding to the center of the Earth are 2.3%and 1.5%,respectively,lower than previously thought.
摘要：A structural search leads to the prediction of a novel alkaline earth nitride BeN_(4)containing a square planar N_(4)^(2-)ring.This compound has a particular chemical bonding pattern giving it potential as a high-energy-density material.The P4/nmm phase of BeN_(4)may be stable under ambient conditions,with a bandgap of 3.72 eV.It is predicted to have high thermodynamic and kinetic stability due to transfer of the outer-shell s electrons of the Be atom to the N_(4)cluster,with the outer-shell 2p orbital accommodating the lone-pair electrons of N_(4)^(2-).The total of sixπelectrons is the most striking feature,indicating that the square planar N_(4)^(2-)exhibits aromaticity.Under ambient conditions,BeN_(4)has a high energy density(3.924 kJ/g relative to Be3N2 and N2 gas),and its synthesis might be possible at pressures above 31.6 GPa.
摘要：Fused silica and KBr samples were irradiated with a 2.7 MeV electron beam.The emission of fused silica and KBr samples in the UV and visible regions was studied under various experimental conditions.Numerical simulation of optical emission was carried out using the GEANT4 computer platform.Simulations of energy spectra and angular distributions of the beam electrons were performed for different target thicknesses.The results reveal the effect of scattering of the beam electrons on the angular distribution of Cherenkov radiation in fused silica samples with thicknesses exceeding the electron path length.
摘要：It has recently been demonstrated experimentally that a turbulent plasma created by the collision of two inhomogeneous,asymmetric,weakly magnetized,laser-produced plasma jets can generate strong stochastic magnetic fields via the small-scale turbulent dynamo mechanism,provided the magnetic Reynolds number of the plasma is sufficiently large.In this paper,we compare such a plasma with one arising from two pre-magnetized plasma jets whose creation is identical save for the addition of a strong external magnetic field imposed by a pulsed magnetic field generator.We investigate the differences between the two turbulent systems using a Thomson-scattering diagnostic,x-ray selfemission imaging,and proton radiography.The Thomson-scattering spectra and x-ray images suggest that the external magnetic field has a limited effect on the plasma dynamics in the experiment.Although the external magnetic field induces collimation of the flows in the colliding plasma jets and although the initial strengths of the magnetic fields arising from the interaction between the colliding jets are significantly larger as a result of the external field,the energies and morphologies of the stochastic magnetic fields post-amplification are indistinguishable.We conclude that,for turbulent laser-plasmas with supercritical magnetic Reynolds numbers,the dynamo-amplified magnetic fields are determined by the turbulent dynamics rather than the seed fields or modest changes in the initial flow dynamics of the plasma,a finding consistent with theoretical expectations and simulations of turbulent dynamos.
摘要：Experiments have identified the Rayleigh–Taylor(RT)instability as one of the greatest obstacles to achieving inertial confinement fusion.Consequently,mitigation strategies to reduce RT growth and fuel–ablator mixing in the hotspot during the deceleration phase of the implosion are of great interest.In this work,the effect of seed magnetic fields on deceleration-phase RT growth are studied in planar and cylindrical geometries under conditions relevant to the National Ignition Facility(NIF)and Omega experiments.The magnetohydrodynamic(MHD)and resistive-MHD capabilities of the FLASH code are used to model imploding cylinders and planar blast-wave-driven targets.Realistic target and laser parameters are presented that suggest the occurrence of morphological differences in late-time RT evolution in the cylindrical NIF case and a measurable difference in spike height of single-mode growth in the planar NIF case.The results of this study indicate the need for target designs to utilize an RT-unstable foam–foam interface in order to achieve sufficient magnetic field amplification to alter RT evolution.Benchmarked FLASH simulations are used to study these magnetic field effects in both resistive and ideal MHD.
摘要：At the Weizmann Institute of Science,a new high-power-laser laboratory has been established that is dedicated to the fundamental aspects of laser–matter interaction in the relativistic regime and aimed at developing compact laser-plasma accelerators for delivering high-brightness beams of electrons,ions,and x rays.The HIGGINS laser system delivers two independent 100 TW beams and an additional probe beam,and this paper describes its commissioning and presents the very first results for particle and radiation beam delivery.
摘要：Single-crystal x-ray diffraction(SCXRD)is an important tool to study the crystal structure and phase transitions of crystalline materials at elevated pressures.The Partnership for eXtreme Xtallography(PX^(2))program at the GSECARS 13-BM-C beamline of the Advanced Photon Source aims to provide state-of-the-art experimental capabilities to determine the crystal structures of materials under extreme conditions using SCXRD.PX^(2) provides a focused x-ray beam(12318μm^(2))at a monochromatic energy of 28.6 keV.High-pressure SCXRD experiments are performed with a six-circle diffractometer and a Pilatus3 photon-counting detector,facilitated by a membrane system for remote pressure control and an online ruby fluorescence system for pressure determination.The efficient,high-quality crystal structure determination at PX^(2) is exemplified by a study of pressure-induced phase transitions in natural ilvaite[CaFe^(2+)_(2 )Fe^(3+)Si_(2)O_(7)O(OH),P2_(1)/a space group].Two phase transitions are observed at high pressure.The SCXRD data confirm the already-known ilvaite-I(P2_(1)/a)→ilvaite-II(Pnam)transformation at 0.4(1)GPa,and,a further phase transition is found to occur at 22.8(2)GPa where ilvaite-II transforms into ilvaite-III(P2_(1)/a).The crystal structure of the ilvaite-III is solved and refined in the P2_(1)/a space group.In addition to the ilvaite-I→ilvaite-II→ilvaite-III phase transitions,two minor structural modifications are observed as discontinuities in the evolution of the FeO6 polyhedral geometries with pressure,which are likely associated with magnetic transitions.
摘要：There are a number of puzzles concerning physics on the scale of nanometers to femtometers,including the neutron lifetime,the proton charge radius,and the possible existence of the deep Dirac level.With the development of high-intensity laser technology,lasers today can induce extremely strong electromagnetic fields.Electrons in the deep shells of atoms as well as the atomic nucleus itself can be affected by these fields.This may provide a new experimental platform for studies of physical processes on the femto-to nanometer scale,where atomic physics and nuclear physics coexist.In this paper,we review possible new opportunities for studying puzzles on the femto-to nanometer scale using highintensity lasers.
摘要：Using a time-dependent density functional theory method,we perform a systematic numerical study of the transition of high-order harmonic generation in neon(Ne)systems from an isolated Ne atom to an extended Ne system of solid density.We show that ionized electrons wander in such extended systems until they meet a nearby ion and collide with it.The maximum energy edge for the main feature of the high-order harmonic spectrum in this“wandering electron”picture is determined as Eedge=Ip+8Up,where Ip is the ionization energy of Ne and Up is the ponderomotive energy delivered by the driving laser.The factor of 8 comes from the maximum kinetic energy of an ionized electron in the driving laser field.Beyond the atomic limit of high-order harmonic spectra,a multiplatform feature is observed,corresponding to re-collisions of ionized electrons with their nearby ions.It is also shown that a Ne simple cubic lattice of appropriate size provides a selection condition for the direction of polarization of high-order harmonics beyond the atomic limit,which may be further used to manipulate the emitted radiation.
摘要：The interaction between a molecular cloud and an external agent(e.g.,a supernova remnant,plasma jet,radiation,or another cloud)is a common phenomenon throughout the Universe and can significantly change the star formation rate within a galaxy.This process leads to fragmentation of the cloud and to its subsequent compression and can,eventually,initiate the gravitational collapse of a stable molecular cloud.It is,however,difficult to study such systems in detail using conventional techniques(numerical simulations and astronomical observations),since complex interactions of flows occur.In this paper,we experimentally investigate the compression of a foam ball by Taylor–Sedov blast waves,as an analog of supernova remnants interacting with a molecular cloud.The formation of a compression wave is observed in the foam ball,indicating the importance of such experiments for understanding how star formation is triggered by external agents.
摘要：The structural evolution of laser-excited systems of gold has previously been measured through ultrafast MeV electron diffraction.However,there has been a long-standing inability of atomistic simulations to provide a consistent picture of the melting process,leading to large discrepancies between the predicted threshold energy density for complete melting,as well as the transition between heterogeneous and homogeneous melting.We make use of two-temperature classical molecular dynamics simulations utilizing three highly successful interatomic potentials and reproduce electron diffraction data presented by Mo et al.[Science 360,1451–1455(2018)].We recreate the experimental electron diffraction data,employing both a constant and temperature-dependent electron–ion equilibration rate.In all cases,we are able to match time-resolved electron diffraction data,and find consistency between atomistic simulations and experiments,only by allowing laser energy to be transported away from the interaction region.This additional energy-loss pathway,which scales strongly with laser fluence,we attribute to hot electrons leaving the target on a timescale commensurate with melting。
摘要：Nonlocal thermal transport in magnetized plasmas is studied theoretically and numerically with the Vlasov–Fokker–Planck(VFP)model,in which the magnetic field has nonzero components both perpendicular to and along the temperature gradient.Nonlocal heat transport is found in both the longitudinal and transverse directions,provided the temperature gradients are sufficiently large.The magnetic field tends to reduce the nonlocality of the thermal transport in the direction perpendicular to the magnetic field,i.e.,the difference between the heat fluxes predicted by the Braginskii theory and the VFP simulation decreases with increasing magnetic field strength.When the initial temperature gradient is steep,the nonlocal heat flux depends not only on the present temperature profile,but also on its time history.Moreover,the contribution of high-order terms in the spherical harmonic expansion of the electron distribution function becomes important for a magnetized plasma,in particular for thermal transport in the direction perpendicular to the temperature gradient.
摘要：We discuss the possibility of realizing time-resolved Kossel diffraction experiments for providing indications on the crystalline order or the periodic structure of a material.We make use of the interaction of short,ultra-intense laser pulses with a solid target,which generates short bursts of hot electrons.Penetrating inside a layered sample(i.e.,a crystal or an artificial multilayer material),these electrons ionize inner-shell electrons so that the subsequent radiative filling of K-shell vacancies results in a strong Kαemission that is enhanced in the Bragg directions corresponding to the period of the material.We present simulations of angle-resolved Kαemission,which displays so-called Kossel patterns around the Bragg angles.We then discuss possible experiments appropriate for laser facilities delivering short and intense pulses.
摘要：Laser-driven neutron sources could offer a promising alternative to those based on conventional accelerator technologies in delivering compact beams of high brightness and short duration.We examine this through particle-in-cell and Monte Carlo simulations that model,respectively,the laser acceleration of protons from thin-foil targets and their subsequent conversion into neutrons in secondary lead targets.Laser parameters relevant to the 0.5 PW LMJ-PETAL and 0.6–6 PW Apollon systems are considered.Owing to its high intensity,the 20-fs-duration 0.6 PW Apollon laser is expected to accelerate protons up to above 100MeV,thereby unlocking efficient neutron generation via spallation reactions.As a result,despite a 30-fold lower pulse energy than the LMJ-PETAL laser,the 0.6 PW Apollon laser should perform comparably well both in terms of neutron yield and flux.Notably,we predict that very compact neutron pulses,of∼10 ps duration and∼100μm spot size,can be released provided the lead convertor target is thin enough(∼100μm).These sources are characterized by extreme fluxes,of the order of 10^(23) n cm^(−2) s^(−1),and even ten times higher when using the 6 PW Apollon laser.Such values surpass those currently achievable at large-scale accelerator-based neutron sources(∼10^(16) n cm^(−2) s^(−1)),or reported from previous laser experiments using low-Z converters(∼10^(18) n cm^(−2) s^(−1)).By showing that such laser systems can produce neutron pulses significantly brighter than existing sources,our findings open a path toward attractive novel applications,such as flash neutron radiography and laboratory studies of heavy-ion nucleosynthesis.
摘要：A Z-pinch dynamic hohlraum can create the high-temperature radiation field required by indirect-drive inertial confinement fusion.A dynamic hohlraum with peak radiation temperature over 300 eV can be obtained with a>50 MA Z-pinch driver according to the scaling law of dynamic hohlraum radiation temperature vs drive current.Based on a uniform 300 eV radiation temperature profile with a width of 10 ns,three double-shell capsules with radii of 2,2.5,and 3 mm are proposed,and the corresponding fusion yields from a one-dimensional calculation are 28.8,56.1,and 101.6 MJ.The implosion dynamics of the 2.5 mm-radius capsule is investigated in detail.At ignition,the areal density of the fuel is about 0.53 g/cm^(2),the fuel pressure is about 80 Gbar,and the central ion temperature is about 4.5 keV,according to the one-dimensional simulation.A two-dimensional simulation indicates that the double-shell capsule can implode nearly spherically when driven by the radiation field of a Z-pinch dynamic hohlraum.The sensitivities of the fusion performance to the radiation temperature profiles and to deviations in the capsule parameter are investigated through one-dimensional simulation,and it is found that the capsule fusion yields are rather stable in a quite large parameter space.A one-dimensional simulation of a capsule embedded in 50 mg/cm^(3)CH foam indicates that the capsule performance does not change greatly in the mimicked environment of a Z-pinch dynamic hohlraum.The double-shell capsules designed here are also applicable to laser indirect-drive inertial fusion,if a laser facility can produce a uniform 300 eV radiation field and sustain it for about 10 ns.
