We present the results of the first commissioning phase of the short-focal-length area of the Apollon laser facility(located in Saclay,France),which was performed with the first available laser beam(F2),scaled to a no...We present the results of the first commissioning phase of the short-focal-length area of the Apollon laser facility(located in Saclay,France),which was performed with the first available laser beam(F2),scaled to a nominal power of 1 PW.Under the conditions that were tested,this beam delivered on-target pulses of 10 J average energy and 24 fs duration.Several diagnostics were fielded to assess the performance of the facility.The on-target focal spot and its spatial stability,the temporal intensity profile prior to the main pulse,and the resulting density gradient formed at the irradiated side of solid targets have been thoroughly characterized,with the goal of helping users design future experiments.Emissions of energetic electrons,ions,and electromagnetic radiation were recorded,showing good laser-to-target coupling efficiency and an overall performance comparable to that of similar international facilities.This will be followed in 2022 by a further commissioning stage at the multipetawatt level.展开更多
Various code development platforms, such as the ATHENA Framework [1] of the ATLAS [2] experiment encounter lengthy compilation/linking times. To augment this situation, the IRIS Development Platform was built as a sof...Various code development platforms, such as the ATHENA Framework [1] of the ATLAS [2] experiment encounter lengthy compilation/linking times. To augment this situation, the IRIS Development Platform was built as a software development framework acting as compiler, cross-project linker and data fetcher, which allow hot-swaps in order to compare various versions of software under test. The flexibility fostered by IRIS allowed modular exchange of software libraries among developers, making it a powerful development tool. The IRIS platform used input data ROOT-ntuples [3];however a new data model is sought, in line with the facilities offered by IRIS. The schematic of a possible new data structuring—as a user implemented object oriented data base, is presented.展开更多
Realizing the full potential of ultrahigh-intensity lasers for particle and radiation generation will require multi-beam arrangements due to technology limitations.Here,we investigate how to optimize their coupling wi...Realizing the full potential of ultrahigh-intensity lasers for particle and radiation generation will require multi-beam arrangements due to technology limitations.Here,we investigate how to optimize their coupling with solid targets.Experimentally,we show that overlapping two intense lasers in a mirror-like configuration onto a solid with a large preplasma can greatly improve the generation of hot electrons at the target front and ion acceleration at the target backside.The underlying mechanisms are analyzed through multidimensional particle-in-cell simulations,revealing that the self-induced magnetic fields driven by the two laser beams at the target front are susceptible to reconnection,which is one possible mechanism to boost electron energization.In addition,the resistive magnetic field generated during the transport of the hot electrons in the target bulk tends to improve their collimation.Our simulations also indicate that such effects can be further enhanced by overlapping more than two laser beams.展开更多
With the much-anticipated multi-petawatt(PW)laser facilities that are coming online,neutron sources with extreme fluxes could soon be in reach.Such sources would rely on spallation by protons accelerated by the high-i...With the much-anticipated multi-petawatt(PW)laser facilities that are coming online,neutron sources with extreme fluxes could soon be in reach.Such sources would rely on spallation by protons accelerated by the high-intensity lasers.These high neutron fluxes would make possible not only direct measurements of neutron capture andβ-decay rates related to the r-process of nucleosynthesis of heavy elements,but also such nuclear measurements in a hot plasma environment,which would be beneficial for s-process investigations in astrophysically relevant conditions.This could,in turn,finally allow possible reconciliation of the observed element abundances in stars and those derived from simulations,which at present show large discrepancies.Here,we review a possible pathway to reach unprecedented neutron fluxes using multi-PW lasers,as well as strategies to perform measurements to investigate the r-and s-processes of nucleosynthesis of heavy elements in cold matter,as well as in a hot plasma environment.展开更多
Recent achievements in laboratory astrophysics experiments with high-power lasers have allowed progress in our understanding of the early stages of star formation.In particular,we have recently demonstrated the possib...Recent achievements in laboratory astrophysics experiments with high-power lasers have allowed progress in our understanding of the early stages of star formation.In particular,we have recently demonstrated the possibility of simulating in the laboratory the process of the accretion of matter on young stars[G.Revet et al.,Sci.Adv.3,e1700982(2017)].The present paper focuses on x-ray spectroscopy methods that allow us to investigate the complex plasma hydrodynamics involved in such experiments.We demonstrate that we can infer the formation of a plasma shell,surrounding the accretion column at the location of impact with the stellar surface,and thus resolve the present discrepancies between mass accretion rates derived from x-ray and optical-radiation astronomical observations originating from the same object.In our experiments,the accretion column ismodeled by having a collimated narrow(1 mm diameter)plasma stream first propagate along the lines of a large-scale external magnetic field and then impact onto an obstacle,mimicking the high-density region of the stellar chromosphere.A combined approach using steady-state and quasi-stationarymodels was successfully applied tomeasure the parameters of the plasma all along its propagation,at the impact site,and in the structure surrounding the impact region.The formation of a hot plasma shell,surrounding the denser and colder core,formed by the incoming stream of matter is observed near the obstacle using x-ray spatially resolved spectroscopy.展开更多
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 t...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.展开更多
Kinetic behaviors of niobium and titanium carbide precipitates in iron are simulated with cluster dynamics.The simulations,carried out in austenite and ferrite for niobium carbides,and in austenite for titanium carbid...Kinetic behaviors of niobium and titanium carbide precipitates in iron are simulated with cluster dynamics.The simulations,carried out in austenite and ferrite for niobium carbides,and in austenite for titanium carbide,are analyzed for dependences on temperature,solute concentration,and initial cluster distribution.The results are presented for different temperatures and solute concentrations,compared to experimental data available.They show little impact of initial cluster distribution beyond a certain relaxation time and that highly dilute alloys with monomers only present a significantly different behavior from denser alloys or ones with different initial cluster distributions.展开更多
Laser irradiation of solid targets can drive short and high-charge relativistic electron bunches over micron-scale acceleration gradients.However,for a long time,this technique was not considered a viable means of ele...Laser irradiation of solid targets can drive short and high-charge relativistic electron bunches over micron-scale acceleration gradients.However,for a long time,this technique was not considered a viable means of electron acceleration due to the large intrinsic divergence(∼50°half-angle)of the electrons.Recently,a reduction in this divergence to 10°–20°half-angle has been obtained,using plasma-based magnetic fields or very high contrast laser pulses to extract the electrons into the vacuum.Here we show that we can further improve the electron beam collimation,down to∼1.5°half-angle,of a high-charge(6 nC)beam,and in a highly reproducible manner,while using standard stand-alone 100 TW-class laser pulses.This is obtained by embedding the laser-target interaction in an external,large-scale(cm),homogeneous,extremely stable,and high-strength(20 T)magnetic field that is independent of the laser.With upcoming multi-PW,high repetition-rate lasers,this technique opens the door to achieving even higher charges(>100 nC).展开更多
Engineered targets are expected to play a key role in future high-power laser experiments calling for joined, extensive knowledge in materials properties, engineering techniques and plasma physics. In this work, we pr...Engineered targets are expected to play a key role in future high-power laser experiments calling for joined, extensive knowledge in materials properties, engineering techniques and plasma physics. In this work, we propose a novel patterning procedure of self-supported 10 μm thick Au and Cu foils for obtaining micrometre-sized periodic gratings as targets for high-power laser applications. Accessible techniques were considered, by using cold rolling, electronbeam lithography and the Ar-ion milling process. The developed patterning procedure allows efficient control of the grating and foil surface on large area. Targets consisting of patterned regions of 450 μm × 450 μm, with 2 μm periodic gratings, were prepared on 25 mm × 25 mm Au and Cu free-standing foils, and preliminary investigations of the microtargets interacting with an ultrashort, relativistic laser pulse were performed. These test experiments demonstrated that,in certain conditions, the micro-gratings show enhanced laser energy absorption and higher efficiency in accelerating charge particle beams compared with planar thin foils of similar thickness.展开更多
Neutron noise spectra in nuclear reactors are a convolution of multiple-induced reactivities.For the IBR-2 pulsed reactor(JINR-Dubna),one part is represented by the reactivities induced by the two moving reflectors,an...Neutron noise spectra in nuclear reactors are a convolution of multiple-induced reactivities.For the IBR-2 pulsed reactor(JINR-Dubna),one part is represented by the reactivities induced by the two moving reflectors,and the other part by other sources that are moderately stable.In the present study,using recordings of the mechanical noise of the two moving reflectors,their non-linear correlations into the power spectra of the reactor are extracted using statistical analysis.The remaining noise sources are moderately stable noise and can be further monitored by other automated reactor diagnoses.展开更多
Laser wakefield accelerators （LWFAs） are considered to be one of the most compeuuve next- generation accelerator candidates. In this paper, we will study the potential high-flux electron beam production of an LWFA d...Laser wakefield accelerators （LWFAs） are considered to be one of the most compeuuve next- generation accelerator candidates. In this paper, we will study the potential high-flux electron beam production of an LWFA driven by petawatt-level laser pulses. In our three-dimensional particle-in-cell simulations, an optimal set of parameters gives -40 nC of charge with 2 PW laser power, thus -400 kA of instantaneous current if we assume the electron beam duration is 100 fs. This high flux and its secondary radiation are widely applicable in nuclear and QED physics, industrial imaging, medical and biological studies.展开更多
The (seldomly quoted) generalised-Heisenberg uncertainty relations are an effect of the quantum correlation coefficient inequalities. The quantum correlation coefficient determines how much a state can be compacted an...The (seldomly quoted) generalised-Heisenberg uncertainty relations are an effect of the quantum correlation coefficient inequalities. The quantum correlation coefficient determines how much a state can be compacted and on what basis. It is shown that?how this can be used to best compress a signal (such as a radio wave, or a 2D laser complex field at a focal plane) while at the same time encrypting the signal.展开更多
High-spin states in 69As were populated via the 40Ca(32S, 3p)69As reaction at 95 MeV beam energy. The 32S beam was provided by the VIVITRON accelerator of the IreS Strasbourg. A target of 1 mg/cm2 With 15 mg/cm2 gold ...High-spin states in 69As were populated via the 40Ca(32S, 3p)69As reaction at 95 MeV beam energy. The 32S beam was provided by the VIVITRON accelerator of the IreS Strasbourg. A target of 1 mg/cm2 With 15 mg/cm2 gold backing was used. Measurements of γ-γand γ-γ-γcoincidences were performed with the EUROBALL展开更多
Real-time evaluation of laser-driven byproducts is crucial for state-of-the-art facilities operating at high repetition rates.This work presents real-time measurements of hard X-rays(bremsstrahlung radiation) generate...Real-time evaluation of laser-driven byproducts is crucial for state-of-the-art facilities operating at high repetition rates.This work presents real-time measurements of hard X-rays(bremsstrahlung radiation) generated from the interaction of high-intensity laser pulses with solid targets in the target normal sheath acceleration regime using a scintillator stack detector. The detector offers insights into the effectiveness of laser–plasma interaction through measured fiuctuations in bremsstrahlung radiation temperature and scintillation light yield on a shot-to-shot basis. Moreover, a strong correlation of the bremsstrahlung measurements(i.e., temperature and yield) with the cutoff energy of laser-driven protons was observed. The scintillator stack detector serves not only as a diagnostic for online monitoring of the laser–plasma interaction but also as a promising tool for estimating proton energy fiuctuations in a non-disruptive manner, which is particularly important when direct proton source characterization is impractical, for example, during experiments aimed at irradiating user samples with the accelerated proton beam.展开更多
Half-lives ofαdecay for Z≥84 nuclei are calculated based on the WKB theory applied for a phenomenological potential barrier composed of a centrifugal contribution and a screened electrostatic interaction represented...Half-lives ofαdecay for Z≥84 nuclei are calculated based on the WKB theory applied for a phenomenological potential barrier composed of a centrifugal contribution and a screened electrostatic interaction represented by a Hulthen potential.For favored decays,the model has a single adjustable parameter associated with the screening of the electrostatic potential.The description of half lives for unfavored decays requires an additional hindrance term.A good agreement with experimental data is obtained in all considered cases.The evolution of the screening parameter for each nucleus revealed its dependence on shell filling.The model is also used for theoretical predictions on a few nuclei with uncertain or incomplete decay information.展开更多
Mass is a fundamental property and an important fingerprint of atomic nucleus.It provides an extremely useful test ground for nuclear models and is crucial to understand energy generation in stars as well as the heavy...Mass is a fundamental property and an important fingerprint of atomic nucleus.It provides an extremely useful test ground for nuclear models and is crucial to understand energy generation in stars as well as the heavy elements synthesized in stellar explosions.Nuclear physicists have been attempting at developing a precise,reliable,and predictive nuclear model that is suitable for the whole nuclear chart,while this still remains a great challenge even in recent days.Here we employ the Fourier spectral analysis to examine the deviations of nuclear mass predictions to the experimental data and to present a novel way for accurate nuclear mass predictions.In this analysis,we map the mass deviations from the space of nucleon number to its conjugate space of frequency,and are able to pin down the main contributions to the model deficiencies.By using the radial basis function approach we can further isolate and quantify the sources.Taking a pedagogical mass model as an example,we examine explicitly the correlation between nuclear effective interactions and the distributions of mass deviations in the frequency domain.The method presented in this work,therefore,opens up a new way for improving the nuclear mass predictions towards a hundred kilo-electron-volt accuracy,which is argued to be the chaos-related limit for the nuclear mass predictions.展开更多
True ternary fission and Tin-accompanied ternary fission of 242Pu are studied by using the'Three Cluster Model'.True ternary fission is considered as a formation of heavy fragments in the region 28≤Z1,Z2,Z3≤...True ternary fission and Tin-accompanied ternary fission of 242Pu are studied by using the'Three Cluster Model'.True ternary fission is considered as a formation of heavy fragments in the region 28≤Z1,Z2,Z3≤38 with comparable masses.The possible fission channels are predicted by the potential-energy calculations.Interaction potentials,Q-values and relative yields for all possible fragmentations in equatorial and collinear configurations are calculated and compared.It is found that ternary fission with formation of a double magic nucleus like 132Sn is more probable than the other fragmentations.Also,the kinetic energies of the fragments for the group Z1=32,Z2=32 and Z3=30 are calculated for all combinations in the collinear geometry as a sequential decay.展开更多
The formation of large size clusters,and/or their relative motion as a possible excitation mode,are suggested to be closely related to the origin of deformation in specific cases,namely the case of two doubly-magic cl...The formation of large size clusters,and/or their relative motion as a possible excitation mode,are suggested to be closely related to the origin of deformation in specific cases,namely the case of two doubly-magic clusters or two clusters with nearby characterization.New lifetime data in N=Z^(76)Sr and^(80)Zr leading to large B(E2)values are reproduced consistently and well within this approach,along with data for a few neighboring N≈Znuclei.These results are compared to previous studies of^(32)S and^(20)Ne and all of them support the ideas of the large-scale cluster approach.展开更多
Fusion-evaporation cross sections of^(238)U(^(9)Be,5n)^(242)Cm are measured over a wide energy range around the Coulomb barrier.These measured cross sections are compared with model calculations using two codes,namely...Fusion-evaporation cross sections of^(238)U(^(9)Be,5n)^(242)Cm are measured over a wide energy range around the Coulomb barrier.These measured cross sections are compared with model calculations using two codes,namely HIVAP2 and KE WPIE2.HIVAP2 calculations overestimate the measured fusion-evaporation cross sections by a factor of approximately 3.In KEWPIE2 calculations,two approaches,namely the Wentzel-Kramers-Brillouin(WKB)approximation and the empirical barrier-distribution(EBD)method,are used for the capture probability;both of them properly describe the measured cross sections.Additionally,fusion cross sections of^(7.9)Be+^(238)Umeas-ured in two experiments are applied to constrain model calculations further through three codes,i.e,HIVAP2,KEWPIE2,and CCFULL.Parameters in these codes are also examined by comparison with measured fusion cross sections.AIll the comparisons indicate that the K EWPIE2 calculations using the WKB approximation agree well with the measured cross sections of both fusion reactions 7.9 Be+^(238)U and the fusion-evaporation reaction 238U(9 Be,5n)242 Cm.Calculations using the fusion code CCFULL are also in good agreement with the measured fusion cross sections of 7.9 Be+^(238)U.展开更多
The excitation function of the 58Ni(n,p)58Co reaction was measured using the well-established neutron activation technique andγ-ray spectroscopy.Neutrons in the energy range of 1.7 to 2.7 MeV were generated using the...The excitation function of the 58Ni(n,p)58Co reaction was measured using the well-established neutron activation technique andγ-ray spectroscopy.Neutrons in the energy range of 1.7 to 2.7 MeV were generated using the 7Li(p,n)reaction.The neutron flux was measured using the standard 115In(n,n’)115mIn monitor reaction.The results of the neutron spectrum averaged cross-section of 58Ni(n,p)58Co reactions were compared with existing cross-section data available in the EXFOR data library as well as with various evaluated data libraries such as ENDF/B-VIII.0,JEFF-3.3,JENDL-4.0,and CENDL-3.2.Theoretical calculations were performed using the nuclear reaction code TALYS.Various nuclear level density(NLD)models were tested,and their results were compared with the present findings.Realistic NLDs were also obtained through the spectral distribution method(SDM).The cross-section results,along with the absolute errors,were obtained by investigating the uncertainty propagation and using the covariance technique.Corrections forγ-ray true coincidence summing,low-energy background neutrons,andγ-ray self attenuation were performed.The experimental cross-section obtained in the present study is consistent with previously published experimental data,evaluated libraries,and theoretical calculations carried out using the TALYS code.展开更多
基金The authors acknowledge the facility and the technical assistance of the national research infrastructureApollon.The authorswould also like to thank all teams of the laboratories that contributed to the success of the facility,i.e.,all of theCILEXconsortium,whichwas established to buildApollon.Thisworkwas supported by funding fromthe European Research Council(ERC)under the European Unions Horizon 2020 research and innovation program(Grant Agreement No.787539,Project GENESIS),and by Grant No.ANR-17-CE30-0026-Pinnacle from the Agence Nationale de la Recherche.We acknowledge,in the framework of ProjectGENESIS,the support provided by Extreme Light InfrastructureNuclear Physics(ELI-NP)Phase II,a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund,and by the Project No.ELI-RO-2020-23,funded by IFA(Romania)to design,build,and test the neutron detectors used in this project,as well as parts of the OTR diagnostic.JIHT RAS team members are supported by the Ministry of Science and Higher Education of the Russian Federation(State Assignment No.075-00460-21-00)The study reported here was also funded by the Russian Foundation for Basic Research,Project No.20-02-00790.The work of the ENEA team members has been carried out within the framework of the EUROfusionConsortiumand has received funding from the Euratom research and training program 2014–2018 and 2019-2020 under grant agreement No.633053.
文摘We present the results of the first commissioning phase of the short-focal-length area of the Apollon laser facility(located in Saclay,France),which was performed with the first available laser beam(F2),scaled to a nominal power of 1 PW.Under the conditions that were tested,this beam delivered on-target pulses of 10 J average energy and 24 fs duration.Several diagnostics were fielded to assess the performance of the facility.The on-target focal spot and its spatial stability,the temporal intensity profile prior to the main pulse,and the resulting density gradient formed at the irradiated side of solid targets have been thoroughly characterized,with the goal of helping users design future experiments.Emissions of energetic electrons,ions,and electromagnetic radiation were recorded,showing good laser-to-target coupling efficiency and an overall performance comparable to that of similar international facilities.This will be followed in 2022 by a further commissioning stage at the multipetawatt level.
文摘Various code development platforms, such as the ATHENA Framework [1] of the ATLAS [2] experiment encounter lengthy compilation/linking times. To augment this situation, the IRIS Development Platform was built as a software development framework acting as compiler, cross-project linker and data fetcher, which allow hot-swaps in order to compare various versions of software under test. The flexibility fostered by IRIS allowed modular exchange of software libraries among developers, making it a powerful development tool. The IRIS platform used input data ROOT-ntuples [3];however a new data model is sought, in line with the facilities offered by IRIS. The schematic of a possible new data structuring—as a user implemented object oriented data base, is presented.
基金supported by the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant Agreement No.787539)funding from EPRSC(Grant Nos.EP/E035728,EP/C003586,and EP/P010059/1)supported by the National Sciences and Engineering Research Council of Canada(NSERC)and Compute Canada(Job:pve-323-ac,PA).
文摘Realizing the full potential of ultrahigh-intensity lasers for particle and radiation generation will require multi-beam arrangements due to technology limitations.Here,we investigate how to optimize their coupling with solid targets.Experimentally,we show that overlapping two intense lasers in a mirror-like configuration onto a solid with a large preplasma can greatly improve the generation of hot electrons at the target front and ion acceleration at the target backside.The underlying mechanisms are analyzed through multidimensional particle-in-cell simulations,revealing that the self-induced magnetic fields driven by the two laser beams at the target front are susceptible to reconnection,which is one possible mechanism to boost electron energization.In addition,the resistive magnetic field generated during the transport of the hot electrons in the target bulk tends to improve their collimation.Our simulations also indicate that such effects can be further enhanced by overlapping more than two laser beams.
基金We acknowledge fruitful discussions with H.P´epin(INRS),V.M´eot,L.Gremillet,X.Davoine(CEA),S.Orlando(INAF),C.Guerrero(Universidad de Sevilla),and Y.Caristan(Universit´e Paris-Saclay).This project received funding from the European Research Council(ERC)under the European Union’s Horizon 2020 Research and Innovation Programme(Grant Agreement No.787539),and was partly conducted within the LABEX Plas@Par project and supported by Grant Nos.11-IDEX-0004-02 and an ANR-17-CE30-0026 PiNNaCLE grant from Agence Nationale de la Recherche(France).I.P.acknowledges the support of ISF Grant No.1135/15.The research leading to these results is supported by Extreme Light Infrastructure Nuclear Physics(ELI-NP)Phase I,a project cofinanced by the Romanian Government and the European Union through the European Regional Development Fund.
文摘With the much-anticipated multi-petawatt(PW)laser facilities that are coming online,neutron sources with extreme fluxes could soon be in reach.Such sources would rely on spallation by protons accelerated by the high-intensity lasers.These high neutron fluxes would make possible not only direct measurements of neutron capture andβ-decay rates related to the r-process of nucleosynthesis of heavy elements,but also such nuclear measurements in a hot plasma environment,which would be beneficial for s-process investigations in astrophysically relevant conditions.This could,in turn,finally allow possible reconciliation of the observed element abundances in stars and those derived from simulations,which at present show large discrepancies.Here,we review a possible pathway to reach unprecedented neutron fluxes using multi-PW lasers,as well as strategies to perform measurements to investigate the r-and s-processes of nucleosynthesis of heavy elements in cold matter,as well as in a hot plasma environment.
基金X-ray data measurement,modeling and analysis were made by the JIHT RAS team with financial support from the Russian Science Foundation(Project No.17-72-20272)The authors thank the entire staff of the ELFIE laser facility at LULI for their support during the experimental preparation and execution.This work was supported by ANR Blanc Grant No.12-BS09-025-01 SILAMPA and has received funding from the European Union’s Horizon 2020 research and innovation program through the European Research Council(ERC,Grant Agreement No.787539)Some work was done within the LABEX Plas@Par project,which is supported by Grant No.11-IDEX-0004-02 from Agence Nationale de la Recherche.The research leading to these results is supported by Extreme Light Infrastructure Nuclear Physics(ELI-NP)Phase I,a project co-financed by the Romanian Government and European Union through the European Regional Development Fund.This work was performed under the auspices of the U.S.Department of Energy by Lawrence Livermore National Laboratory under Contract No.DE-AC52-07NA27344.
文摘Recent achievements in laboratory astrophysics experiments with high-power lasers have allowed progress in our understanding of the early stages of star formation.In particular,we have recently demonstrated the possibility of simulating in the laboratory the process of the accretion of matter on young stars[G.Revet et al.,Sci.Adv.3,e1700982(2017)].The present paper focuses on x-ray spectroscopy methods that allow us to investigate the complex plasma hydrodynamics involved in such experiments.We demonstrate that we can infer the formation of a plasma shell,surrounding the accretion column at the location of impact with the stellar surface,and thus resolve the present discrepancies between mass accretion rates derived from x-ray and optical-radiation astronomical observations originating from the same object.In our experiments,the accretion column ismodeled by having a collimated narrow(1 mm diameter)plasma stream first propagate along the lines of a large-scale external magnetic field and then impact onto an obstacle,mimicking the high-density region of the stellar chromosphere.A combined approach using steady-state and quasi-stationarymodels was successfully applied tomeasure the parameters of the plasma all along its propagation,at the impact site,and in the structure surrounding the impact region.The formation of a hot plasma shell,surrounding the denser and colder core,formed by the incoming stream of matter is observed near the obstacle using x-ray spatially resolved spectroscopy.
基金supported by funding from the European Research Council(ERC)under the European Unions Horizon 2020 research and innovation program(Grant Agreement No.787539)The computational resources of this work were supported by the National Sciences and Engineering Research Council of Canada(NSERC)and Compute Canada(Job Grant No.pve-323-ac)+4 种基金Part of the experimental system is covered by a patent(No.1000183285,2013,INPI-France)The FLASH software used was developed,in part,by the DOE NNSA ASC-and the DOE Office of Science ASCR-supported Flash Center for Computational Science at the University of ChicagoWe thank J.L.Dubois for providing us EOS and opacities.The research leading to these results is supported by Extreme Light Infrastructure Nuclear Physics(ELI-NP)Phase II,a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund,and by the Project No.ELIRO-2020-23 funded by IFA(Romania)IHT RAS team members are supported by the Ministry of Science and Higher Education of the Russian Federation(State Assignment No.075-00460-21-00)The study reported here was funded by the Russian Foundation for Basic Research,Project No.19-32-60008.
文摘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.
基金the CAS-TWAS President’s Fellowship Programme for this doctoral fellowship(Grant No.2016CTF004)。
文摘Kinetic behaviors of niobium and titanium carbide precipitates in iron are simulated with cluster dynamics.The simulations,carried out in austenite and ferrite for niobium carbides,and in austenite for titanium carbide,are analyzed for dependences on temperature,solute concentration,and initial cluster distribution.The results are presented for different temperatures and solute concentrations,compared to experimental data available.They show little impact of initial cluster distribution beyond a certain relaxation time and that highly dilute alloys with monomers only present a significantly different behavior from denser alloys or ones with different initial cluster distributions.
基金supported by Grant Nos.11-IDEX-0004-02 and ANR-17-CE30-0026-Pinnacle from Agence Nationale de la Recherchethe European Union’s Horizon 2020 research and innovation program under Grant Agreement No.654148 Laserlab-Europe+3 种基金the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant Agreement No.787539)This work was supported by the Ministry of Education and Science of the Russian Federation under Contract No.14.Z50.31.0007The work of JIHT RAS team was done under financial support of the Russian Science Foundation(Grant No.17-72-20272)The research leading to these results is supported by Extreme Light Infrastructure Nuclear Physics(ELI-NP)Phase I,a project co-financed by the Romanian Government and European Union through the European Regional Development Fund.
文摘Laser irradiation of solid targets can drive short and high-charge relativistic electron bunches over micron-scale acceleration gradients.However,for a long time,this technique was not considered a viable means of electron acceleration due to the large intrinsic divergence(∼50°half-angle)of the electrons.Recently,a reduction in this divergence to 10°–20°half-angle has been obtained,using plasma-based magnetic fields or very high contrast laser pulses to extract the electrons into the vacuum.Here we show that we can further improve the electron beam collimation,down to∼1.5°half-angle,of a high-charge(6 nC)beam,and in a highly reproducible manner,while using standard stand-alone 100 TW-class laser pulses.This is obtained by embedding the laser-target interaction in an external,large-scale(cm),homogeneous,extremely stable,and high-strength(20 T)magnetic field that is independent of the laser.With upcoming multi-PW,high repetition-rate lasers,this technique opens the door to achieving even higher charges(>100 nC).
基金supported by the ELI-NP Phase Ⅱ project,co-financed by the Romanian Government and the European Union through the European Regional Development Fund-the Competitiveness Operational Programme(contract No.1/07.07.2016,COP,ID 1334)Funding from the National Program‘Installations and Strategic Objectives of National Interest’and‘Nucleu’project PN19060105 of the Romanian Governmentfunding from the European Union Framework Programme for Research and Innovation Horizon 2020 under grant agreement No.871161.
文摘Engineered targets are expected to play a key role in future high-power laser experiments calling for joined, extensive knowledge in materials properties, engineering techniques and plasma physics. In this work, we propose a novel patterning procedure of self-supported 10 μm thick Au and Cu foils for obtaining micrometre-sized periodic gratings as targets for high-power laser applications. Accessible techniques were considered, by using cold rolling, electronbeam lithography and the Ar-ion milling process. The developed patterning procedure allows efficient control of the grating and foil surface on large area. Targets consisting of patterned regions of 450 μm × 450 μm, with 2 μm periodic gratings, were prepared on 25 mm × 25 mm Au and Cu free-standing foils, and preliminary investigations of the microtargets interacting with an ultrashort, relativistic laser pulse were performed. These test experiments demonstrated that,in certain conditions, the micro-gratings show enhanced laser energy absorption and higher efficiency in accelerating charge particle beams compared with planar thin foils of similar thickness.
基金Supported by the Romanian National Authority for Scientific Research,CNCS-UEFISCDI,under Grant No PN-II-ID-PCE-2011-3-0323the JINR-Dubna order Nr.71,item 21/2012.
文摘Neutron noise spectra in nuclear reactors are a convolution of multiple-induced reactivities.For the IBR-2 pulsed reactor(JINR-Dubna),one part is represented by the reactivities induced by the two moving reflectors,and the other part by other sources that are moderately stable.In the present study,using recordings of the mechanical noise of the two moving reflectors,their non-linear correlations into the power spectra of the reactor are extracted using statistical analysis.The remaining noise sources are moderately stable noise and can be further monitored by other automated reactor diagnoses.
基金supported by Extreme Light Infrastructure- Nuclear Physics (ELI-NP) Phase Ⅱa project co-financed by the Romanian Government and European Union through the European Regional Development FundThe EPOCH code project was funded by the UK EPSRC grants EP/G054950/1, EP/ G056803/1, EP/G055165/1 and EP/ M022463/1
文摘Laser wakefield accelerators （LWFAs） are considered to be one of the most compeuuve next- generation accelerator candidates. In this paper, we will study the potential high-flux electron beam production of an LWFA driven by petawatt-level laser pulses. In our three-dimensional particle-in-cell simulations, an optimal set of parameters gives -40 nC of charge with 2 PW laser power, thus -400 kA of instantaneous current if we assume the electron beam duration is 100 fs. This high flux and its secondary radiation are widely applicable in nuclear and QED physics, industrial imaging, medical and biological studies.
文摘The (seldomly quoted) generalised-Heisenberg uncertainty relations are an effect of the quantum correlation coefficient inequalities. The quantum correlation coefficient determines how much a state can be compacted and on what basis. It is shown that?how this can be used to best compress a signal (such as a radio wave, or a 2D laser complex field at a focal plane) while at the same time encrypting the signal.
文摘High-spin states in 69As were populated via the 40Ca(32S, 3p)69As reaction at 95 MeV beam energy. The 32S beam was provided by the VIVITRON accelerator of the IreS Strasbourg. A target of 1 mg/cm2 With 15 mg/cm2 gold backing was used. Measurements of γ-γand γ-γ-γcoincidences were performed with the EUROBALL
基金the ELIMAIA experimental team and the L3-HAPLS laser team for the support provided during the experimentfunded by the Ministry of Education, Youth and Sports of the Czech Republic by the project ‘Advanced Research Using High Intensity Laser Produced Photons and Particles’ (CZ.02.1.01/0.0/0.0/16_019/0000789)supported by the European Structural and Investment Fund and the Czech Ministry of Education, Youth and Sports (Project International mobility MSCA-IF IV FZUCZ.02.2.69/0.0/0.0/20-079/0017754)。
文摘Real-time evaluation of laser-driven byproducts is crucial for state-of-the-art facilities operating at high repetition rates.This work presents real-time measurements of hard X-rays(bremsstrahlung radiation) generated from the interaction of high-intensity laser pulses with solid targets in the target normal sheath acceleration regime using a scintillator stack detector. The detector offers insights into the effectiveness of laser–plasma interaction through measured fiuctuations in bremsstrahlung radiation temperature and scintillation light yield on a shot-to-shot basis. Moreover, a strong correlation of the bremsstrahlung measurements(i.e., temperature and yield) with the cutoff energy of laser-driven protons was observed. The scintillator stack detector serves not only as a diagnostic for online monitoring of the laser–plasma interaction but also as a promising tool for estimating proton energy fiuctuations in a non-disruptive manner, which is particularly important when direct proton source characterization is impractical, for example, during experiments aimed at irradiating user samples with the accelerated proton beam.
文摘Half-lives ofαdecay for Z≥84 nuclei are calculated based on the WKB theory applied for a phenomenological potential barrier composed of a centrifugal contribution and a screened electrostatic interaction represented by a Hulthen potential.For favored decays,the model has a single adjustable parameter associated with the screening of the electrostatic potential.The description of half lives for unfavored decays requires an additional hindrance term.A good agreement with experimental data is obtained in all considered cases.The evolution of the screening parameter for each nucleus revealed its dependence on shell filling.The model is also used for theoretical predictions on a few nuclei with uncertain or incomplete decay information.
基金supported by the National Program on Key Basic Research Project of China(2013CB834400)the National Natural Science Foundation of China(11205004,11305161,11335002,11475014,11575002,and 11411130147)+2 种基金the Natural Science Foundation of Anhui Province(1708085QA10)the RIKEN iTHES ProjectiTHEMS Program
文摘Mass is a fundamental property and an important fingerprint of atomic nucleus.It provides an extremely useful test ground for nuclear models and is crucial to understand energy generation in stars as well as the heavy elements synthesized in stellar explosions.Nuclear physicists have been attempting at developing a precise,reliable,and predictive nuclear model that is suitable for the whole nuclear chart,while this still remains a great challenge even in recent days.Here we employ the Fourier spectral analysis to examine the deviations of nuclear mass predictions to the experimental data and to present a novel way for accurate nuclear mass predictions.In this analysis,we map the mass deviations from the space of nucleon number to its conjugate space of frequency,and are able to pin down the main contributions to the model deficiencies.By using the radial basis function approach we can further isolate and quantify the sources.Taking a pedagogical mass model as an example,we examine explicitly the correlation between nuclear effective interactions and the distributions of mass deviations in the frequency domain.The method presented in this work,therefore,opens up a new way for improving the nuclear mass predictions towards a hundred kilo-electron-volt accuracy,which is argued to be the chaos-related limit for the nuclear mass predictions.
文摘True ternary fission and Tin-accompanied ternary fission of 242Pu are studied by using the'Three Cluster Model'.True ternary fission is considered as a formation of heavy fragments in the region 28≤Z1,Z2,Z3≤38 with comparable masses.The possible fission channels are predicted by the potential-energy calculations.Interaction potentials,Q-values and relative yields for all possible fragmentations in equatorial and collinear configurations are calculated and compared.It is found that ternary fission with formation of a double magic nucleus like 132Sn is more probable than the other fragmentations.Also,the kinetic energies of the fragments for the group Z1=32,Z2=32 and Z3=30 are calculated for all combinations in the collinear geometry as a sequential decay.
基金Partly supported by the U.S.Department of Energy,Office of Science,Office of Nuclear Physics(DE-AC02-06CH11357)。
文摘The formation of large size clusters,and/or their relative motion as a possible excitation mode,are suggested to be closely related to the origin of deformation in specific cases,namely the case of two doubly-magic clusters or two clusters with nearby characterization.New lifetime data in N=Z^(76)Sr and^(80)Zr leading to large B(E2)values are reproduced consistently and well within this approach,along with data for a few neighboring N≈Znuclei.These results are compared to previous studies of^(32)S and^(20)Ne and all of them support the ideas of the large-scale cluster approach.
基金the National Natural Science Foundation of China(12005314,11805289,11875328,11775316)the ELI-NP Phase II,a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund-the Competitiv eness Operational Programme(1/07.07.2016,COP,ID 1334)。
文摘Fusion-evaporation cross sections of^(238)U(^(9)Be,5n)^(242)Cm are measured over a wide energy range around the Coulomb barrier.These measured cross sections are compared with model calculations using two codes,namely HIVAP2 and KE WPIE2.HIVAP2 calculations overestimate the measured fusion-evaporation cross sections by a factor of approximately 3.In KEWPIE2 calculations,two approaches,namely the Wentzel-Kramers-Brillouin(WKB)approximation and the empirical barrier-distribution(EBD)method,are used for the capture probability;both of them properly describe the measured cross sections.Additionally,fusion cross sections of^(7.9)Be+^(238)Umeas-ured in two experiments are applied to constrain model calculations further through three codes,i.e,HIVAP2,KEWPIE2,and CCFULL.Parameters in these codes are also examined by comparison with measured fusion cross sections.AIll the comparisons indicate that the K EWPIE2 calculations using the WKB approximation agree well with the measured cross sections of both fusion reactions 7.9 Be+^(238)U and the fusion-evaporation reaction 238U(9 Be,5n)242 Cm.Calculations using the fusion code CCFULL are also in good agreement with the measured fusion cross sections of 7.9 Be+^(238)U.
基金One of the authors(A.H.)sincerely acknowledges the Department of Science and Technology(DST),Government of Indiafor the INSPIRE Fellowship award(No.DST/INSPIRE Fellowship/2019/IF190924)+1 种基金partial support from the SERBwith grants No.SIR/2022/000566 and CRG/2021/000101,respectively。
文摘The excitation function of the 58Ni(n,p)58Co reaction was measured using the well-established neutron activation technique andγ-ray spectroscopy.Neutrons in the energy range of 1.7 to 2.7 MeV were generated using the 7Li(p,n)reaction.The neutron flux was measured using the standard 115In(n,n’)115mIn monitor reaction.The results of the neutron spectrum averaged cross-section of 58Ni(n,p)58Co reactions were compared with existing cross-section data available in the EXFOR data library as well as with various evaluated data libraries such as ENDF/B-VIII.0,JEFF-3.3,JENDL-4.0,and CENDL-3.2.Theoretical calculations were performed using the nuclear reaction code TALYS.Various nuclear level density(NLD)models were tested,and their results were compared with the present findings.Realistic NLDs were also obtained through the spectral distribution method(SDM).The cross-section results,along with the absolute errors,were obtained by investigating the uncertainty propagation and using the covariance technique.Corrections forγ-ray true coincidence summing,low-energy background neutrons,andγ-ray self attenuation were performed.The experimental cross-section obtained in the present study is consistent with previously published experimental data,evaluated libraries,and theoretical calculations carried out using the TALYS code.
