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| 1 | Detailed characterization of a laboratory magnetized supercritical collisionless shock and of the associated proton energization显示文摘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. | W.Yao A.Fazzini S.N.Chen K.Burdonov P.Antici J.B´eard S.Bolaños A.Ciardi R.Diab E.D.Filippov S.Kisyov V.Lelasseux M.Miceli Q.Moreno V.Nastasa S.Orlando S.Pikuz D.C.Popescu G.Revet X.Ribeyre E.d’Humi`eres J.Fuchs | 2022 | Matter and Radiation at Extremes2022，7，1： | 0 |
| 2 | X-ray spectroscopy evidence for plasma shell formation in experiments modeling accretion columns in young stars显示文摘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. | E.D.Filippov I.Yu.Skobelev G.Revet S.N.Chen B.Khiar A.Ciardi D.Khaghani D.P.Higginson S.A.Pikuz J.Fuchs | 2019 | Matter and Radiation at Extremes2019，4，6： | 0 |
| 3 | Highly-collimated, high-charge and broadband MeV electron beams produced by magnetizing solids irradiated by high-intensity lasers显示文摘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). | S.Bolaños J.Beard G.Revet S.N.Chen S.Pikuz E.Filippov M.Safronova M.Cerchez O.Willi M.Starodubtsev J.Fuchs | 2019 | Matter and Radiation at Extremes2019，4，4： | 0 |
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