Publications

2021

• On the study of hydrodynamic instabilities in the presence of background magnetic fields in high-energy-density plasmas
  
  • Manuel M. J. E
  • Khiar B
  • Rigon G
  • Albertazzi B
  • Klein S R
  • Kroll F
  • Brack F-E
  • Michel T
  • Mabey P
  • Pikuz S
  • Williams J C
  • Koenig M
  • Casner A
  • Kuranz C C
  Matter and Radiation at Extremes, AIP Publishing, 2021, 6. Blast-wave-driven hydrodynamic instabilities are studied in the presence of a background B-field through experiments and simulations in the high-energy-density (HED) physics regime. In experiments conducted at the Laboratoire pour l’utilisation des lasers intenses (LULI), a laser driven shock-tube platform was used to generate a hydrodynamically unstable interface with a prescribed sinusoidal surface perturbation, and short-pulse x-ray radiography was used to characterize the instability growth with and without a 10-T B-field. The LULI experiments were modeled in FLASH using resistive and ideal magnetohydrodynamics (MHD), and comparing the experiments and simulations suggests that the Spitzer model implemented in FLASH is necessary and sufficient for modeling these planar systems. These results suggest insufficient amplification of the seed B-field, due to resistive diffusion, to alter the hydrodynamic behavior. Although the ideal-MHD simulations did not represent the experiments accurately, they suggest that similar HED systems with dynamic plasma-β(2μ0ρv2/B2) values of less than ∼100 can reduce the growth of blast-wave-driven Rayleigh–Taylor instabilities. These findings validate the resistive-MHD FLASH modeling that is being used to design future experiments for studying B-field effects in HED plasmas. (10.1063/5.0025374)
  DOI : 10.1063/5.0025374
• Ultrashort high energy electron bunches from tunable surface plasma waves driven with laser wavefront rotation
  
  • Marini S
  • Kleij P S
  • Pisani F
  • Amiranoff F
  • Grech M
  • Macchi A
  • Raynaud Michèle
  • Riconda C
  Physical Review E, American Physical Society (APS), 2021, 103. We propose to use ultrahigh intensity laser pulses with wave-front rotation (WFR) to produce short, ultraintense surface plasma waves (SPW) on grating targets for electron acceleration. Combining a smart grating design with optimal WFR conditions identified through simple analytical modeling and particle-in-cell simulation allows us to decrease the SPW duration (down to a few optical cycles) and increase its peak amplitude. In the relativistic regime, for Iλ 2 0 = 3.4 × 10 19 W/cm 2 μm 2 , such SPW are found to accelerate high charge (few 10 s of pC), high energy (up to 70 MeV), and ultrashort (few fs) electron bunches. (10.1103/physreve.103.l021201)
  DOI : 10.1103/physreve.103.l021201
• Electrical conductivity of warm dense silica from double-shock experiments
  
  • Guarguaglini M.
  • Soubiran F.
  • Hernandez J.-A.
  • Benuzzi-Mounaix A.
  • Bolis R.
  • Brambrink E.
  • Vinci T.
  • Ravasio A.
  Nature Communications, Nature Publishing Group, 2021, 12 (1), pp.840. Understanding materials behaviour under extreme thermodynamic conditions is fundamental in many branches of science, including High-Energy-Density physics, fusion research, material and planetary science. Silica (SiO2) is of primary importance as a key component of rocky planets' mantles. Dynamic compression is the most promising approach to explore molten silicates under extreme conditions. Although most experimental studies are restricted to the Hugoniot curve, a wider range of conditions must be reached to distill temperature and pressure effects. Here we present direct measurements of equation of state and two-colour reflectivity of double-shocked α-quartz on a large ensemble of thermodynamic conditions, which were until now unexplored. Combining experimental reflectivity data with numerical simulations we determine the electrical conductivity. The latter is almost constant with pressure while highly dependent on temperature, which is consistent with simulations results. Based on our findings, we conclude that dynamo processes are likely in Super-Earths' mantles. (10.1038/s41467-021-21046-1)
  DOI : 10.1038/s41467-021-21046-1
• X-ray radiography based on the phase-contrast imaging with using LiF detector
  
  • Makarov S S
  • Pikuz T A
  • Buzmakov A V
  • Chernyaev A P
  • Mabey P
  • Vinci T
  • Rigon G
  • Albertazzi B
  • Casner A
  • Bouffetier V
  • Kodama R
  • Katagiri K
  • Kamimura N
  • Umeda Y
  • Ozaki N
  • Falize E
  • Poujade O
  • Togashi T
  • Yabashi M
  • Yabuuchi T
  • Inubushi Y
  • Miyanishi K
  • Sueda K
  • Manuel M
  • Gregori G
  • Koenig M
  • Pikuz S A
  Journal of Physics: Conference Series, IOP Science, 2021, 1787. An x-ray radiography technique based upon phase contrast imaging using a lithium fluoride detector has been demonstrated for goals of high energy density physics experiments. Based on the simulation of propagation an x-ray free-electron laser beam through a testobject, the visibility of phase-contrast image depending on an object-detector distance was investigated. Additionally, the metrological capabilities of a lithium fluoride crystal as a detector were demonstrated. (10.1088/1742-6596/1787/1/012027)
  DOI : 10.1088/1742-6596/1787/1/012027
• Digital micromirror device for holographic and Fourier optics applications
  
  • Douet Brice
  • Tedoldi Téo
  • Kabacinski Adeline
  • Morana Ambra
  • Gallot Guilhem
  • Bouganne Raphaël
  Emergent Scientist, EDP Sciences, 2021, 5 (4), pp.1-7. The electromagnetic wavefront diffracted by an object carries information about the shape of the object from which the wave was emitted. Being able to record the phase and intensity of such a wave thus allows to reconstruct the object from the information carried by the wave, even if the object is no longer present. Among the reconstruction techniques, holography plays a big part. However the waves may experience a great variety of distortions on their way from the object to the measurement apparatus. Thus being able to shape the wavefront at will is key in holography. Micromirror light modulators are powerful tools for that matter and are well known for holographic applications. This paper explores the fundamental principles for digitally reconstructing a precise image of an object, but also for digitally correcting an imperfectly shaped wavefront, by exploiting the diffraction properties of light on a reflective surface. The methods presented here have been implemented as part of practical work for 2nd year students at the Ecole Polytechnique (last year of undergraduate program). (10.1051/emsci/2021003)
  DOI : 10.1051/emsci/2021003
• Exploring the Atwood-number dependence of the highly nonlinear Rayleigh-Taylor instability regime in high-energy-density conditions
  
  • Rigon G.
  • Albertazzi B.
  • Mabey P.
  • Michel Th
  • Falize E.
  • Bouffetier V.
  • Ceurvorst L.
  • Masse L.
  • Koenig M.
  • Casner A.
  Physical Review E, American Physical Society (APS), 2021, 104 (4). We experimentally study the late time, highly nonlinear regime of the Rayleigh-Taylor Instability in a decelerating phase. A series of laser-driven experiments is performed on the LULI2000 laser, in which the initial Atwood number is varied by adjusting the decelerating medium density. The high power laser is used in a direct drive configuration to put into motion a solid target. Its rear side, which initially possesses a two-dimensional machined sinusoidal perturbations, expands and decelerates into a foam leading to a Rayleigh-Taylor unstable situation. The interface position and morphology are measured by time-resolved x-ray radiography. We develop a simple Atwood dependent model describing the motion of the decelerating interface, from which its acceleration history is obtained. The measured amplitude of the instability, or mixing zone width, is then compared with late time acceleration dependent Rayleigh-Taylor instability models. The shortcoming of this classical models, when applied to high energy density conditions, is shown. This calls into question their uses for systems, where a shock wave is present, such as those found in laboratory astrophysics or in Inertial Confinement Fusion. (10.1103/PhysRevE.104.045213)
  DOI : 10.1103/PhysRevE.104.045213
• Generation of optically synchronized pump-signal beams for ultrafast OPCPA via the optical Kerr effect
  
  • Alexandridi Christina
  • Delen Xavier
  • Druon Frédéric
  • Georges Patrick
  • Martin Luc
  • Mathieu François
  • Papadopoulos Dimitris
  Optics Letters, Optical Society of America - OSA Publishing, 2021, 46 (9), pp.2035. In recent years, multi-PW laser installations have achieved unprecedented peak powers opening new horizons to laser-matter interaction studies. Ultra broadband and extreme temporal contrast pulses requirements make the optical parametric chirped pulse amplification (OPCPA) in the few-ps regime, the key technology in these systems. To guarantee however a high fidelity output, the OPCPA requires excellent synchronization between the pump and the signal pulses. Here, we propose a new highly versatile architecture for the generation of optically synchronized pumpsignal pairs based on the Kerr shutter effect. We obtained >550 µJ pump pulses of 12 ps duration at 532 nm optically synchronized with a typical ultrashort CPA source at 800 nm. As a proof of principle demonstration, our system has been also used for the amplification of ∼20 µJ ultra-broadband pulses based on an OPCPA setup. (10.1364/OL.425237)
  DOI : 10.1364/OL.425237
• Bremsstrahlung emission and plasma characterization driven by moderately relativistic laser–plasma interactions
  
  • Singh Sushil
  • Armstrong Chris D.
  • Kang Ning
  • Ren Lei
  • Liu Huiya
  • Hua Neng
  • Rusby Dean R.
  • Klimo Ondřej
  • Versaci Roberto
  • Zhang Yan
  • Sun Mingying
  • Zhu Baoqiang
  • Lei Anle
  • Ouyang Xiaoping
  • Lancia Livia
  • Garcia Alejandro Laso
  • Wagner Andreas
  • Cowan Thomas
  • Zhu Jianqiang
  • Schlegel Theodor
  • Weber Stefan
  • Mckenna Paul
  • Neely David
  • Tikhonchuk Vladimir
  • Kumar Deepak
  Plasma Physics and Controlled Fusion, IOP Publishing, 2021, 63 (3), pp.035004. Relativistic electrons generated by the interaction of petawatt-class short laser pulses with solid targets can be used to generate bright X-rays via bremsstrahlung. The efficiency of laser energy transfer into these electrons depends on multiple parameters including the focused intensity and pre-plasma level. This paper reports experimental results from the interaction of a high intensity petawatt-class glass laser pulses with solid targets at a maximum intensity of $10^{19}$ W/cm$^2$. In-situ measurements of specularly reflected light are used to provide an upper bound of laser absorption and to characterize focused laser intensity, the pre-plasma level and the generation mechanism of second harmonic light. The measured spectrum of electrons and bremsstrahlung radiation provide information about the efficiency of laser energy transfer. (10.1088/1361-6587/abcf7e)
  DOI : 10.1088/1361-6587/abcf7e
• Selective Ion Acceleration by Intense Radiation Pressure
  
  • Mcilvenny A.
  • Doria D.
  • Romagnani L.
  • Ahmed H.
  • Booth N.
  • Ditter E.J.
  • Ettlinger O.C.
  • Hicks G.S.
  • Martin P.
  • Scott G.G.
  • Williamson S.D.R.
  • Macchi A.
  • Mckenna P.
  • Najmudin Z.
  • Neely D.
  • Kar S.
  • Borghesi M.
  Physical Review Letters, American Physical Society, 2021, 127 (19), pp.194801. We report on the selective acceleration of carbon ions during the interaction of ultrashort, circularly polarized and contrast-enhanced laser pulses, at a peak intensity of <math display="inline"><mrow><mn>5.5</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>20</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi mathvariant="normal">W</mi><mo>/</mo><msup><mrow><mi>cm</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math>, with ultrathin carbon foils. Under optimized conditions, energies per nucleon of the bulk carbon ions reached significantly higher values than the energies of contaminant protons (<math display="inline"><mrow><mn>33</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi><mo>/</mo><mi>nucleon</mi></mrow></math> vs 18 MeV), unlike what is typically observed in laser-foil acceleration experiments. Experimental data, and supporting simulations, emphasize different dominant acceleration mechanisms for the two ion species and highlight an (intensity dependent) optimum thickness for radiation pressure acceleration; it is suggested that the preceding laser energy reaching the target before the main pulse arrives plays a key role in a preferential acceleration of the heavier ion species. (10.1103/PhysRevLett.127.194801)
  DOI : 10.1103/PhysRevLett.127.194801
• Metallization of Shock-Compressed Liquid Ammonia
  
  • Ravasio A.
  • Bethkenhagen M.
  • Hernandez J.-A.
  • Benuzzi-Mounaix A.
  • Datchi F.
  • French M.
  • Guarguaglini M.
  • Lefevre F.
  • Ninet S.
  • Redmer R.
  • Vinci T.
  Physical Review Letters, American Physical Society, 2021, 126 (2), pp.025003. Ammonia is predicted to be one of the major components in the depths of the ice giant planets Uranus and Neptune. Their dynamics, evolution, and interior structure are insufficiently understood and models rely imperatively on data for equation of state and transport properties. Despite its great significance, the experimentally accessed region of the ammonia phase diagram today is still very limited in pressure and temperature. Here we push the probed regime to unprecedented conditions, up to ∼350 GPa and ∼40000K. Along the Hugoniot, the temperature measured as a function of pressure shows a subtle change in slope at ∼7000K and ∼90 GPa, in agreement with ab initio simulations we have performed. This feature coincides with the gradual transition from a molecular liquid to a plasma state. Additionally, we performed reflectivity measurements, providing the first experimental evidence of electronic conduction in high-pressure ammonia. Shock reflectance continuously rises with pressure above 50 GPa and reaches saturation values above 120 GPa. Corresponding electrical conductivity values are up to 1 order of magnitude higher than in water in the 100 GPa regime, with possible significant contributions of the predicted ammonia-rich layers to the generation of magnetic dynamos in ice giant interiors. (10.1103/PhysRevLett.126.025003)
  DOI : 10.1103/PhysRevLett.126.025003
• Bremsstrahlung cannon design for Shock Ignition relevant regime
  
  • Koester P
  • Baffigi F
  • Cristoforetti G
  • Labate L
  • Gizzi L A
  • Baton S. D.
  • Koenig M
  • Colaïtis A
  • Batani D
  • Casner A
  • Raffestin D
  • Tentori A
  • Trela J
  • Rousseaux C
  • Boutoux G
  • Brygoo S
  • Jacquet L
  • Reverdin C
  • Le Bel E
  • Le-Deroff L
  • Theobald W
  • Shigemori K
  Review of Scientific Instruments, American Institute of Physics, 2021, 92, pp.013501. (10.1063/5.0022030)
  DOI : 10.1063/5.0022030
• Design and commissioning of a neutron counter adapted to high-intensity laser matter interactions
  
  • Lelasseux V.
  • Söderström P.-A.
  • Aogaki S.
  • Burdonov K.
  • Cerchez M.
  • Chen S.
  • Dorard S.
  • Fazzini A.
  • Gugiu M.
  • Pikuz S.
  • Rotaru F.
  • Willi O.
  • Negoita F.
  • Fuchs J.
  Review of Scientific Instruments, American Institute of Physics, 2021, 92. The advent of multi-PW laser facilities world-wide opens new opportunities for nuclear physics. With this perspective, we developed a neutron counter taking into account the specifics of a high-intensity laser environment. Using GEANT4 simulations and prototype testings, we report on the design of a modular neutron counter based on boron-10 enriched scintillators and a high-density polyethylene moderator. This detector has been calibrated using a plutonium-beryllium neutron source and commissioned during an actual neutron-producing laser experiment at the LULI2000 facility (France). An overall efficiency of 4.37(59)% has been demonstrated during calibration with a recovery time of a few hundred microseconds after laser-plasma interaction. (10.1063/5.0057828)
  DOI : 10.1063/5.0057828
• Laser-driven collisionless shock acceleration of protons from gas jets tailored by one or two nanosecond beams
  
  • Bonvalet J
  • Loiseau P
  • Marquès J.-R
  • Atukpor E
  • d'Humières E
  • Domange J
  • Forestier-Colleoni P
  • Hannachi F
  • Lancia L
  • Raffestin D
  • Tarisien M
  • Tikhonchuk V
  • Nicolaï P
  Physics of Plasmas, American Institute of Physics, 2021, 28 (11), pp.113102. It was proposed recently that laser-ion acceleration in gas jets may be significantly improved if each side of a gas jet target is tailored by an auxiliary nanosecond laser pulse [Marque `s et al., Phys. Plasmas 28, 023103 (2021)]. In the present study, the proton acceleration by electrostatic shock in these one-or two-side tailored plasmas is investigated using particle-in-cell simulations. It is demonstrated that the formation of a thin plasma layer with a steep density profile and a maximum density of the order of the critical density strongly improves the proton acceleration in the forward direction with a maximum ion energy of tens of MeV with mildly relativistic laser pulses. Proton acceleration up to tens of MeV is predicted using realistic plasma density profiles obtained from tailored gas jet targets compared to a few MeV reported in other publications. (10.1063/5.0062503)
  DOI : 10.1063/5.0062503
• Impact of the laser spatio-temporal shape on Breit–Wheeler pair production
  
  • Mercuri-Baron A.
  • Grech M.
  • Niel F.
  • Grassi A.
  • Lobet M.
  • Di Piazza A.
  • Riconda C.
  New Journal of Physics, Institute of Physics: Open Access Journals, 2021, 23 (8), pp.085006. The forthcoming generation of multi-petawatt lasers opens the way to abundant pair production by the nonlinear Breit–Wheeler process, i.e. the decay of a photon into an electron–positron pair inside an intense laser field. In this paper we explore the optimal conditions for Breit–Wheeler pair production in the head-on collision of a laser pulse with gamma photons. The role of the laser peak intensity versus the focal spot size and shape is examined keeping a constant laser energy to match experimental constraints. A simple model for the soft-shower case, where most pairs originate from the decay of the initial gamma photons, is derived. This approach provides us with a semi-analytical model for more complex situations involving either Gaussian or Laguerre–Gauss (LG) laser beams. We then explore the influence of the order of the LG beams on pair creation. Finally we obtain the result that, above a given threshold, a larger spot size (or a higher order in the case of LG laser beams) is more favorable than a higher peak intensity. Our results match very well with three-dimensional particle-in-cell simulations and can be used to guide upcoming experimental campaigns. (10.1088/1367-2630/ac1975)
  DOI : 10.1088/1367-2630/ac1975
• Inefficient Magnetic-Field Amplification in Supersonic Laser-Plasma Turbulence
  
  • Bott A F A
  • Chen L
  • Boutoux G
  • Caillaud T
  • Duval A
  • M. Koenig
  • Khiar B
  • Lantuéjoul I
  • Le-Deroff L
  • Reville B
  • Rosch R
  • Ryu D
  • Spindloe C
  • Vauzour B
  • Villette B
  • Schekochihin A A
  • Lamb D Q
  • Tzeferacos P
  • Gregori G
  • Casner A
  Physical Review Letters, American Physical Society, 2021, 127 (17), pp.175002. We report a laser-plasma experiment that was carried out at the LMJ-PETAL facility and realized the first magnetized, turbulent, supersonic (Maturb ≈ 2.5) plasma with a large magnetic Reynolds number (Rm ≈ 45) in the laboratory. Initial seed magnetic fields were amplified, but only moderately so, and did not become dynamically significant. A notable absence of magnetic energy at scales smaller than the outer scale of the turbulent cascade was also observed. Our results support the notion that moderately supersonic, low-magnetic-Prandtl-number plasma turbulence is inefficient at amplifying magnetic fields compared to its subsonic, incompressible counterpart. (10.1103/physrevlett.127.175002)
  DOI : 10.1103/physrevlett.127.175002
• Direct measurement of non-thermal electron acceleration from magnetically driven reconnection in a laboratory plasma
  
  • Chien Abraham
  • Gao Lan
  • Zhang Shu
  • Ji Hantao
  • Blackman Eric
  • Daughton William
  • Stanier Adam
  • Le Ari
  • Guo Fan
  • Follett Russ
  • Chen Hui
  • Fiksel Gennady
  • Bleotu Gabriel
  • Cauble Robert
  • Chen Sophia
  • Fazzini Alice
  • Flippo Kirk
  • French Omar
  • Froula Dustin
  • Fuchs Julien
  • Fujioka Shinsuke
  • Hill Kenneth
  • Klein Sallee
  • Kuranz Carolyn
  • Nilson Philip
  • Rasmus Alexander
  • Takizawa Ryunosuke
  Nature Physics, Nature Publishing Group [2005-....], 2021, 19, pp.254–262. Magnetic reconnection rapidly converts magnetic energy into some combination of plasma flow energy, thermal energy and non-thermal energetic particles. Various reconnection acceleration mechanisms have been theoretically proposed and numerically studied in different collisionless and low-β environments, where β refers to the plasma-to-magnetic pressure ratio. These mechanisms include Fermi acceleration, betatron acceleration, parallel electric field acceleration along magnetic fields and direct acceleration by the reconnection electric field. However, none of them have been experimentally confirmed, as the direct observation of non-thermal particle acceleration in laboratory experiments has been difficult due to short Debye lengths for in situ measurements and short mean free paths for ex situ measurements. Here we report the direct measurement of accelerated non-thermal electrons from magnetically driven reconnection at low β in experiments using a laser-powered capacitor coil platform. We use kilojoule lasers to drive parallel currents to reconnect megagauss-level magnetic fields in a quasi-axisymmetric geometry. The angular dependence of the measured electron energy spectrum and the resulting accelerated energies, supported by particle-in-cell simulations, indicate that the mechanism of direct electric field acceleration by the out-of-plane reconnection electric field is at work. Scaled energies using this mechanism show direct relevance to astrophysical observations. (10.1038/s41567-022-01839-x)
  DOI : 10.1038/s41567-022-01839-x
• Laboratory disruption of scaled astrophysical outflows by a misaligned magnetic field
  
  • Revet G.
  • Khiar B.
  • Filippov E.
  • Argiroffi C.
  • Béard Jérome
  • Bonito R.
  • Cerchez M.
  • Chen S.N.
  • Gangolf T.
  • Higginson D.P.
  • Mignone A.
  • Olmi B.
  • Ouillé M.
  • Ryazantsev S.N.
  • Skobelev I.Yu.
  • Safronova M.I.
  • Starodubtsev M.
  • Vinci T.
  • Willi O.
  • Pikuz S.
  • Orlando S.
  • Ciardi A.
  • Fuchs J.
  Nature Communications, Nature Publishing Group, 2021, 12 (1), pp.762. Mass outflow is a common process in astrophysical objects. Here the authors investigate in which conditions an astrophysically-scaled laser-produced plasma flow can be collimated and evolves in the presence of a misaligned external magnetic field. (10.1038/s41467-021-20917-x)
  DOI : 10.1038/s41467-021-20917-x
• X-ray powder diffraction in reflection geometry on multi-beam kJ-type laser facilities
  
  • Denoeud A.
  • Hernandez J.-A.
  • Vinci T.
  • A. Benuzzi-Mounaix
  • Brygoo S.
  • Berlioux A.
  • Lefevre F.
  • Sollier A.
  • Videau L.
  • Ravasio A.
  • Guarguaglini M.
  • Duthoit L.
  • Loison Didier
  • Brambrink E.
  Review of Scientific Instruments, American Institute of Physics, 2021, 92 (1), pp.013902. An ultrafast x-ray powder diffraction setup for laser-driven dynamic compression has been developed at the LULI2000 laser facility. X-ray diffraction is performed in reflection geometry from a quasi-monochromatic laser-generated plasma x-ray source. In comparison to a transmission geometry setup, this configuration allows us to probe only a small portion of the compressed sample, as well as to shield the detectors against the x-rays generated by the laser-plasma interaction on the front side of the target. Thus, this new platform facilitates probing of spatially and temporarily uniform thermodynamic conditions and enables us to study samples of a large range of atomic numbers, thicknesses, and compression dynamics. As a proof-of-concept, we report direct structural measurements of the bcc-hcp transition both in shock and ramp-compressed polycrystalline iron with diffraction signals recorded between 2θ ∼30° and ∼150°. In parallel, the pressure and temperature history of probed samples is measured by rear-side visible diagnostics (velocimetry and pyrometry). (10.1063/5.0020261)
  DOI : 10.1063/5.0020261
• Key parameters for surface plasma wave excitation in the ultra-high intensity regime
  
  • Marini S
  • Kleij P S
  • Amiranoff F
  • Grech M
  • Riconda C
  • Raynaud Michèle
  Physics of Plasmas, American Institute of Physics, 2021, 28 (7), pp.073104. Ultra-short high-power lasers can deliver extreme light intensities (!10 20 W/cm 2 and 30 f s) and drive large amplitude Surface Plasma Wave (SPW) at over-dense plasma surface. The resulting current of energetic electron has great interest for applications, potentially scaling with the laser amplitude, provided that the laser-plasma transfer to the accelerated particles mediated by SPW is still efficient at ultra-high intensity. By means of particle-in-cell simulations, we identify the best condition for SPW excitation and show a strong correlation between the optimum surface plasma wave excitation angle and the laser's angle of incidence that optimize the electron acceleration along the plasma surface. We also discuss how plasma density and plasma surface shape can be adjusted in order to push to higher laser intensity the limit of surface plasma wave excitation. Our results open the way to new experiments on forthcoming multi-petawatt laser systems. (10.1063/5.0052599)
  DOI : 10.1063/5.0052599
• Ultrafast olivine-ringwoodite transformation during shock compression
  
  • Okuchi Takuo
  • Seto Yusuke
  • Tomioka Naotaka
  • Matsuoka Takeshi
  • Albertazzi Bruno
  • Hartley Nicholas J
  • Inubushi Yuichi
  • Katagiri Kento
  • Kodama Ryosuke
  • Pikuz Tatiana A
  • Purevjav Narangoo
  • Miyanishi Kohei
  • Sato Tomoko
  • Sekine Toshimori
  • Sueda Keiichi
  • Tanaka Kazuo A
  • Tange Yoshinori
  • Togashi Tadashi
  • Umeda Yuhei
  • Yabuuchi Toshinori
  • Yabashi Makina
  • Ozaki Norimasa
  Nature Communications, Nature Publishing Group, 2021, 12, pp.4305. Meteorites from interplanetary space often include high-pressure polymorphs of their constituent minerals, which provide records of past hypervelocity collisions. These collisions were expected to occur between kilometre-sized asteroids, generating transient high-pressure states lasting for several seconds to facilitate mineral transformations across the relevant phase boundaries. However, their mechanisms in such a short timescale were never experimentally evaluated and remained speculative. Here, we show a nanosecond transformation mechanism yielding ringwoodite, which is the most typical high-pressure mineral in meteorites. An olivine crystal was shock-compressed by a focused high-power laser pulse, and the transformation was time-resolved by femtosecond diffractometry using an X-ray free electron laser. Our results show the formation of ringwoodite through a faster, diffusionless process, suggesting that ringwoodite can form from collisions between much smaller bodies, such as metre to submetre-sized asteroids, at common relative velocities. Even nominally unshocked meteorites could therefore contain signatures of high-pressure states from past collisions. (10.1038/s41467-021-24633-4)
  DOI : 10.1038/s41467-021-24633-4
• Numerical study of Langmuir wave coalescence in laser-plasma interaction
  
  • Pérez F
  • Amiranoff F
  • Briand C
  • Depierreux S
  • Grech M
  • Lancia L
  • Loiseau P
  • Marquès J.-R
  • Riconda C
  • Vinci T
  Physics of Plasmas, American Institute of Physics, 2021. Type-III-burst radio signals can be mimicked in the laboratory via laser-plasma interaction. Instead of an electron beam generating Langmuir waves (LW) in the interplanetary medium, the LWs are created by a laser interacting with a millimeter-sized plasma through the stimulated Raman instability. In both cases, the LWs feed the Langmuir decay instability which scatters them in several directions. The resulting LWs may couple to form electromagnetic emission at twice the plasma frequency, which has been detected in the interplanetary medium, and recently in a laboratory laser experiment [Marquès et al. Phys. Rev. Lett. 124, 135001 (2020)]. This article presents the first numerical analysis of this laser configuration using particle-in-cell simulations, providing details on the wave spectra that are too difficult to measure in experiments. The role of some parameters is addressed, with a focus on laser intensity, in order to illustrate the behavior of the electromagnetic emission's angular distribution and polarization. (10.1063/5.0037028)
  DOI : 10.1063/5.0037028
• Laboratory evidence for proton energization by collisionless shock surfing
  
  • Yao W.
  • Fazzini A.
  • Chen S.N.
  • Burdonov K.
  • Antici P.
  • Béard J.
  • Bolaños S.
  • Ciardi A.
  • Diab R.
  • Filippov E.D.
  • Kisyov S.
  • Lelasseux V.
  • Miceli M.
  • Moreno Q.
  • Nastasa V.
  • Orlando S.
  • Pikuz S.
  • Popescu D.C.
  • Revet G.
  • Ribeyre X.
  • d'Humières E.
  • Fuchs J.
  Nature Physics, Nature Publishing Group [2005-....], 2021, 17 (10), pp.1177-1182. Proton acceleration by a super-critical collisionless shock is observed in laboratory experiments, and numerical simulations suggest shock surfing as the underlying acceleration mechanism. (10.1038/s41567-021-01325-w)
  DOI : 10.1038/s41567-021-01325-w
• XFEL and HHG interaction with matter: Effects of ultrashort pulses and random spikes
  
  • Rosmej F.
  • Astapenko V.
  • Khramov E. S
  Matter and Radiation at Extremes, AIP Publishing, 2021, 6 (3), pp.034001. The theory of photoionization describing the interaction of x-ray free-electron laser (XFEL) pulses and high-harmonic-generated (HHG) radiation is generalized to ultrashort laser pulses, where the concept of the standard ionization probability per unit time in Fermi’s golden rule and in Einstein’s theory breaks down. Numerical calculations carried out in terms of a generalized photoionization probability for the total duration of pulses in the near-threshold regime demonstrate essentially nonlinear behavior, while absolute values may change by orders of magnitude for typical XFEL and HHG pulses. XFEL self-amplified spontaneous emission pulses are analyzed to reveal general features of photoionization for random and regular spikes: the dependences of the nonlinear photoionization probability on carrier frequency and spike duration are very similar, allowing an analytical expectation value approach that is valid even when there is only limited knowledge of random and regular parameters. Numerical simulations carried out for typical parameters demonstrate excellent agreement. (10.1063/5.0046040)
  DOI : 10.1063/5.0046040
• Over-critical sharp-gradient plasma slab produced by the collision of laser-induced blast-waves in a gas jet: Application to high-energy proton acceleration
  
  • Marquès J.R.
  • Loiseau P.
  • Bonvalet J.
  • Tarisien M.
  • d'Humières E.
  • Domange J.
  • Hannachi F.
  • Lancia L.
  • Larroche O.
  • Nicolaï P.
  • Puyuelo-Valdes P.
  • Romagnani L.
  • Santos J.J.
  • Tikhonchuk V.
  Physics of Plasmas, American Institute of Physics, 2021, 28 (2), pp.023103. Generating thin and high density plasma slabs at a high repetition rate is a key issue for ultra-high intensity laser applications, such as plasma photonics, electron acceleration by few laser-cycle pulses, or collisionless shock acceleration of protons to high energies. In this paper, we present a scheme to generate such plasma slabs. It is based on the propagation and collision in a gas jet of two counter-propagating blast waves (BWs). Each BW is launched by a sudden and local heating induced by a nanosecond laser beam that propagates along the side of the jet. The resulting cylindrical BW expands perpendicular to the beam. The shock front, which is bent by the gas jet density gradient, pushes and compresses the plasma toward the jet center. By using two parallel ns laser beams, one on each side of the gas jet, this scheme enables us to tailor independently two opposite sides of the jet, while avoiding the damage risks associated with counterpropagating laser beams. A parametric study is performed using two and three dimensional hydrodynamic (single fluid), as well as kinetic (Fokker–Planck), simulations. This study shows that the BW bending combined with the collision in a stagnation regime increases the density by more than ten times and generates a very thin (down to few micrometers), near to over-critical plasma slab with a high density contrast (>100) and a lifetime of a few hundred picoseconds. Two dimensional particle-in-cell simulations are, then, used to study the influence of the plasma tailoring on proton acceleration by a high-intensity sub-picosecond laser pulse. It is shown that tailoring the plasma, not only at the entrance but also at the exit side of the picosecond-pulse, enhances the proton beam collimation and increases significantly the number of high energy protons, and their maximum energy. (10.1063/5.0031313)
  DOI : 10.1063/5.0031313