Publications

2026

• Kα X-ray generation from a debris-free cryogenic argon jet driven by high-repetition-rate femtosecond lasers
  
  • Merdji-Larue A.
  • Lechevalier Corentin
  • Goede S.
  • Iwan B.
  • Andrieu Jordan
  • Turianska O.
  • Fsaifes Ihsan
  • Pillegowda M.
  • San Miguel Claveria P.
  • Kovacev M.
  • Chanteloup Jean-Christophe
  • Fajardo M.
  • Zeitoun Philippe
  • Merdji Hamed
  , 2026 (EM1B.3). <div><p>We investigate 3 keV, Kα X-ray generation from a debris-free cryogenic argon jet irradiated by high-repetition-rate femtosecond laser. Measurements from 100 kHz to 2 MHz reveal efficient X-ray production and fluxes approaching 10⁹ photons•s⁻¹•sr⁻¹ at MHz repetition rates.</p></div>
• Real-time piston phase measurement of coherent beam combined lasers using PISTIL interferometry
  
  • Ledent Cyril
  • Balosso Robin
  • Fsaifes Ihsan
  • Jaeck Julien
  • Bellanger Cindy
  • Primot Jérôme
  • Chanteloup Jean-Christophe
  , 2026. <div><p>We demonstrate real-time piston phase measurement for coherent beam combining architecture using the PISTIL interferometer on a segmented laser wave front.</p></div>
• Reduced-complexity femtosecond diffractive beam combination of a fiber laser array
  
  • Ayeb Achraf
  • Fsaifes Ihsan
  • Chanteloup Jean-Christophe
  • Shollenbarger Carson
  • Schulz Dan
  • Sipes Donald
  , 2026 (ATu2A.6). <div><p>We report on femtosecond coherent beam combining of 7 fiber amplifiers using diffractive optics. Power scaling of fiber amplifiers, rather than their number, through CPTEC technology is presented.</p></div>
• Ultrafast filamentation in air at a MHz-range repetition rate
  
  • Lechevalier Corentin
  • Fsaifes Ihsan
  • Andrieu Jordan
  • Frigerio Leandro
  • Burger Milos
  • Jovanovic Igor
  • Chanteloup Jean-Christophe
  , 2026 (ATu2A.4). <div><p>Plasma filaments in air are generated using a versatile coherently combined ultrashort fiber laser, reaching the highest repetition rate of 524 kHz reported to date. Cumulative effects on the filament dynamics are investigated.</p></div>
• Vector beams generation with large aperture pixelated liquid crystal cells on a coherently combined digital laser
  
  • Lechevalier Corentin
  • Ayeb Achraf
  • Andrieu Jordan
  • Ranély-Vergé-Dépré Claude-Alban
  • Boer Gerben
  • Fsaifes Ihsan
  • Chanteloup Jean-Christophe
  , 2026. <div><p>We demonstrate vector beams generation on a coherently combined digital laser using two largeaperture liquid-crystal SLM. This approach enables arbitrary polarization control across the Poincaré sphere and extends the laser toward complete electric field control.</p></div>
• Near-unity-efficiency gas gratings for ultraviolet, visible, and infrared high-power lasers
  
  • Ou K.
  • Rajesh H.
  • Cao S.
  • Chakraborty D.
  • Perez-Ramirez V M
  • Singh D.
  • Redshaw C.
  • Dedeler P.
  • Oudin A.
  • Kur E.
  • Wang M M
  • Mikhailova J M
  • Lancia L.
  • Riconda C.
  • Michel P.
  • Edwards M R
  Optica, Optical Society of America - OSA Publishing, 2026, 13 (9), pp.1726. Interfering deep ultraviolet (DUV) lasers can induce substantial density modulations in an ozone-doped gas flow via photochemical reactions, creating 1 volume diffraction gratings. These transient optics are immune to target debris and shrapnel and feature orders of magnitude higher damage thresholds than conventional solid optics, providing a promising method for efficiently 2 manipulating high-energy lasers. In this work, we describe gas gratings that can efficiently diffract probe beams across a variety of wavelengths and pulse durations, ranging from deep ultraviolet to near-infrared and from nanosecond to femtosecond, achieving a full beam diffraction efficiency up to 99% while preserving the focusability and wavefront quality. In addition, we present a comprehensive characterization of the performance of the gas gratings under various experimental conditions, including imprint fluence, gas composition, and grating geometries, showing significant enhancement of this process with the addition of carbon dioxide. We 3 also demonstrate stable performance over hours of operation. Our results validate a previously developed theoretical model and suggest optimal parameters to efficiently scale gas gratings to high-energy applications. (10.1364/optica.590554)
  DOI : 10.1364/optica.590554
• Accessing the fundamental link between atomic populations and frequency distribution of spectral lines of ions in dense plasmas
  
  • P. Condamine F.
  • Galtier E.
  • Renner O.
  • Khaghani D.
  • Gournay L.
  • Vachal P.
  • Cunningham E.
  • Dyer G.
  • Greenberg M.
  • Nagler B.
  • Lee H.-J.
  • H. Glenzer S.
  • P. Marques J.
  • Indelicato Paul
  • V. Demura A.
  • S. Lisitsa V.
  • A. Vainshtein L.
  • B. Rosmej F.
  Communications Physics, Nature Research, 2026. Dense plasmas enable to test our fundamental understanding of matter but a lack of data hindered searches of new physics in the past. A game changer is the new and unique Stanford-Linear-Accelerator-Center allowing X-ray line-shape-resolved resonance pumping via a combination of the self-seeded Linac-Coherent-Light-Source beam with an optical-laser produced dense plasma: Non-isolated atom models can now be benchmarked via the spectral distribution. High-precision spectroscopy reveals significant and simultaneous redistribution in population and frequency for transitions in He-like Vanadium. A critical principal quantum number is identified above which a strong intensity enhancement of higher lying Rydberg-lines appears although the corresponding ionic levels are not directly pumped. The Rydberg-lines themselves show significant distortions of their spectral distribution. We determine their frequency distributions with a precision of 0.2eV at 6.6keV and observe significant systematic deviations from available numerical methods. Our data question the current understanding how local thermodynamic equilibrium can be achieved. They also serve as a crucial benchmark for quantum theories in dense plasmas and may sparkle new theoretical developments, important for fundamental studies and applications in astrophysics and high-energy-density science. (10.1038/s42005-026-02798-y)
  DOI : 10.1038/s42005-026-02798-y
• Collision of two radial rarefaction waves in unmagnetized ambient plasma: effects of the ambient plasma density
  
  • François Margaux
  • Dieckmann Mark
  • Romagnani Lorenzo
  • Ribeyre Xavier
  • d'Humières Emmanuel
  , 2026. The expansion of two circular rarefaction waves in vacuum or in a thin ambient plasma is examined with particle-in-cell simulations that resolve two spatial dimensions. In the simulation with no ambient plasma, the rarefaction waves interpenetrate near the symmetry line between both rarefaction wave centers. The exponential density decrease of rarefaction waves with distance implies that the sum of their density does not lead to a density maximum near the symmetry line. The absence of a density maximum, which would yield a repelling electric potential for the inflowing rarefaction wave ions near the symmetry line, and the high interpenetration speed of the ion beams lead to ion-ion instabilities rather than shocks in the overlap layer. The simulations with ambient plasma show that the rarefaction waves pile up the ions of the ambient plasma near the symmetry line. A localized piston of hot ambient ions forms. If its density is large enough, its thermoelectric field allows reverse shocks to grow in the rarefaction waves. These reverse shocks move slowly in the simulation frame and enclose a slab of downstream plasma. A decrease in the speed of the rarefaction wave ions upstream of the shocks with time leads to their collapse.
• On the generation of astrophysically-relevant intermittent magnetic turbulence in the laboratory
  
  • Cohen Itamar
  • Yao Weipeng
  • Bott Archie F.A
  • Chen Sophia N
  • Mirkovic Nikola
  • Béard Jerome
  • Bleotu Petrisor Gabriel
  • Giubegal Georgiana
  • Talposi Anda-Maria
  • Heller Yoav
  • Lacoste Clément
  • Antici Patrizio
  • Caprioli Damiano
  • d'Humieres Emmanuel
  • Malka Victor
  • Marcowith Alexandre
  • Tesileanu Ovidiu
  • Ruszkowski Mateusz
  • Kempski Philipp
  • Alexandrova Olga
  • Fuchs Julien
  , 2026. Intermittent magnetic turbulence, namely the presence of non-ordered and clusterized fields, is a ubiquitous phenomenon in space and astrophysical plasmas. It is currently understood that it plays a crucial role in the dynamics of astrophysical systems at all scales, from influencing the evolution of the cosmos as a whole to governing local particle acceleration. While there is direct evidence of turbulence in the solar wind, and despite progress obtained through multi-wavelength observations, most of our knowledge of it outside the solar system derives from indirect evidence, through modeling. Here we show that magnetic turbulence, that quantitatively matches that measured in space, can be reproduced in the laboratory. Starting from a homogeneous magnetized plasma, we randomly perturb it using a speckled laser beam. Using proton radiography, we can follow the development and quantitatively characterize the produced intermittent turbulence from its inception.
• Simultaneous PW-scale laser driven MeV X-ray and neutron beam characterization for dual radiography capability
  
  • Cohen I.
  • Yao W.
  • Mirkovic N.
  • Antici P.
  • Auge G.
  • Bleotu P. -G.
  • Catabi T.
  • Chen S. N.
  • Ciardi A.
  • Condamine F.
  • Ducasse Quentin
  • Fauvel G.
  • Gambicchia Robin
  • Giubega G.
  • Gremillet L.
  • Gugiu M.
  • Iancu V.
  • Mix L.T.
  • Ristic Yoann
  • Sangwan D.
  • Sheats M.
  • Trompier François
  • Tudor L.
  • Turiel S.
  • Verstraeten G.
  • Vinchon Thibaut
  • Pomerantz I.
  • Tesileanu O.
  • Fuchs J.
  , 2026. Laser-driven, high-brilliance secondary sources (electrons, ions, neutrons, X-rays) open new perspectives for compact material probing and imaging of high-speed events. A key advantage is their ability to perform multiplexed probing, as these sources are generated simultaneously in a single shot using a single laser beam. Here, we report the first quantitative measurements of photon spectra (0.1--100 MeV) and angular distributions in the petawatt interaction regime, using an ultra-intense ($&gt;10^{21}\,\rm W/cm^2$), ultra-short (24~fs) laser pulse. These results are complemented by the characterization of simultaneously produced MeV neutrons. We demonstrate that these neutrons, once moderated, can enable in-depth material identification via resonance transmission analysis. This work highlights the potential of compact, ultrashort-pulse PW lasers for dual neutron and X-ray radiography of dense materials. (10.48550/arXiv.2604.15365)
  DOI : 10.48550/arXiv.2604.15365
• Ultrafast filamentation in the air at 333 kHz
  
  • Lechevalier Corentin
  • Fsaifes Ihsan
  • Andrieu Jordan
  • Ayeb Achraf
  • Frigerio Leandro
  • Burger Milos
  • Jovanovic Igor
  • Chanteloup Jean-Christophe
  , 2026. The authors experimentally investigate the cumulative effects of a femtosecond pulse train on plasma filament generation in air at a repetition rate of 333 kHz — the highest reported to date for air filamentation — in contrast to conventional studies employing Ti:sapphire systems at ≲1 kHz. The source is a coherently beam-combined Yb-doped fiber laser in a chirped-pulse amplification architecture, delivering ~5 ms bursts at 5 Hz (1666 pulses at 210 µJ each), with post-compression from 350 fs to ~65 fs via self-phase modulation in an argon-filled multipass cell to reach GW-level peak powers. The beam is expanded to 43 mm (1/e²) and focused by a 350 mm lens, producing a visible filament exceeding the incident-beam Rayleigh range by more than a factor of 30, diagnosed with an ICCD camera and a SID4 wavefront sensor mutually synchronized to isolate a single pulse within the burst. Because the 3 µs inter-pulse interval is much shorter than the ~ms thermal diffusion time of air, cumulative effects arise: filaments lengthen progressively through the burst, and two distinct temporal regimes are resolved from the probe phase shift — an ionization-dominated regime in which the density depletion tracks the filament profile, followed by thermal diffusion becoming dominant toward the end of the burst. The authors note that further work is underway to clarify the interplay between repetition rate, pulse selection, and the filamentation process itself.
• Investigating Spatio-Temporal Dynamics and Self-Steepening in Multi-Pass Cells
  
  • Couairon Arnaud
  • Fsaifes Ihsan
  • Chanteloup Jean-Christophe
  • Houard Aurélien
  , 2026, pp.35. Driven by the need for robust, high-energy pulse compression methods that circumvent bulk damage limitations, multi-pass cells (MPCs) have emerged as a premier technology for spectral broadening, yet the complex coupling between spatial self-focusing and temporal self-steepening remains under-explored [1-3]. In this work, I will present a comprehensive numerical study using a full radial 3D propagation code to evaluate nonlinear pulse evolution in gas-filled MPCs with self-steepening enabled. I will present a systematic comparison of a spatially resolved model against traditional 1D approximations, illustrating the breakdown of 1D theory under intense spatial-temporal clustering and localized self-focusing. Furthermore, I will analyze the impact of input peak power, the accumulated nonlinear phase across consecutive roundtrips, the cell geometry (specifically sweeping the cavity length to mirror curvature ratio (L/R) from near-confocal to near-concentric configurations), and the gas pressure on the resulting blue-shifted spectral asymmetry and post-compression pulse quality. These results show how spatial mode dynamics directly alter temporal shock formation, providing concrete design rules to optimize spectral broadening and minimize uncompressible phase pedestals in next-generation MPC architectures.
• Ab initio description of warm dense matter applied to the physics of giant planets
  
  • Bethkenhagen Mandy
  • Preising Martin
  • Redmer Ronald
  Living Reviews in Computational Astrophysics, Springer, 2026, 12. <div><p>Today, more than 6000 exoplanets are known after the first detection of an extrasolar planet around a main sequence star in 1995. Among them are representatives of new planetary classes such as Super-Earths and Mini-Neptunes, in addition to those already known from the solar system: rocky planets (Mercury, Earth, Venus, Mars), gas giants (Jupiter, Saturn), and ice giants (Uranus, Neptune). In order to understand the formation of planets, their interior structure and composition, thermal evolution and magnetic field, precise data on the equation of state, the transport coefficients, and the optical properties of the most abundant planetary materials are necessary. Relevant temperatures and densities cover a wide range from cold and dilute molecular clouds or planetary atmospheres up to warm and dense planetary cores. Ab initio simulations allow to determine thermophysical properties of warm dense matter with high precision. In this review we give an introduction into the ab initio methods and demonstrate their capacity for planetary physics by showing exemplary results for the thermophysical properties of key materials such as H-He (gas giants) and H-C-N-O mixtures (ice giants). Based on these results, advanced models for the interior structure of planets, their thermal evolution, and their magnetic field can be developed.</p></div> (10.1007/s41115-026-00030-w)
  DOI : 10.1007/s41115-026-00030-w
• Initial Performance of the E320 Tracker
  
  • Borysov Oleksandr
  • Corde Sébastien
  • Evenzur Gal
  • Knetsch Alexander
  • Levi Alon
  • Meuren Sebastian
  • Nofech-Mozes Nathaly
  • Rajkovic Ivan
  • Rego Sheldon
  • Reis David A
  • Santra Arka
  • Smorodnikova Tania
  • Storey Doug W
  • Tal Hod Noam
  • Urmanov Roman
  , 2026. Our recent study discussed the prospects for measuring single positrons produced in electron-laser collisions via the nonlinear Breit-Wheeler deep-tunneling process in the SLAC Experiment 320 at the FACET-II RF LINAC. In this work, we demonstrate how a tracking detector, that is a scaled-down version of the one discussed in the prospective simulation study, enables the measurement. This prototype detector, installed in Aug 2024, is built out of five layers of single ALPIDE chips. The data are taken from several standalone runs completed in Nov 2024 and Feb 2025. We use positrons generated through conversion of Bremsstrahlung photons as a proxy to the nonlinear Breit-Wheeler process. These positrons are produced by the beam electrons in a thin Beryllium foil close to the experiment's interaction point. The tracking approach used in this initial work is based on a Hough-Transform seeding algorithm followed by a straight line fit confined to the detector volume. Even with this relatively simple approach, we are able to measure a signal rate of $(1.20\pm0.06_{stat.}\pm0.56_{syst.})\times10^{-1}$ positrons per shot. This signal rate is comparable to the nonlinear Breit-Wheeler rate expected in the main experiment. Notably, the measurement is achieved under an extreme, unprecedented background hit density of ~1.7/mm$^2$, unlike the main experiment, where at least a twice lower density is expected. This large background is mostly due to secondary particles produced when the large flux of Bremsstrahlung photons interacts with the material of the beamline elements. When the foil is retracted, the false-positive signal rate is shown to be four orders of magnitude smaller than the signal rate. We further show that the high spatial tracking resolution of ~5 micron allows to characterize the positrons' spectra. The results are compared to simulations, which are found to be compatible with the data.
• Développement des concepts de radiographie X par contraste de phase et diffraction cohérente
  
  • de Chevron Villette Raphaël
  , 2026. L’étude de l’interaction de lasers de puissance avec la matière constitue un enjeu majeur pour les futures expériences de fusion par confinement inertiel prévues sur le Laser Mégajoule (LMJ), avec notamment pour objectif de comprendre finement l’ensemble des mécanismes physiques mis en jeu. Parmi les diagnostics disponibles, la radiographie X par contraste d’absorption occupe aujourd’hui une place centrale. Elle permet de sonder la matière dense avec une bonne résolution spatiale, mais demeure limitée par un contraste insuffisant pour les matériaux faiblement absorbants et par une interprétation parfois ambiguë des images. Afin de dépasser ces verrous, ce travail propose une approche fondée sur une description ondulatoire de la formation d’image, articulée autour de deux axes complémentaires. Le premier repose sur le contraste de phase, qui exploite les effets de réfraction des rayons X pour renforcer la sensibilité aux variations d’indice, améliorant ainsi de manière significative le contraste et la résolution des structures observées. Le second s’appuie sur la diffraction cohérente, où les propriétés de l’objet sont encodées quantitativement dans une figure de diffraction. Cette approche permet d’accéder à une information plus riche, au prix cependant d’une reconstruction indirecte. Dans ce manuscrit, nous présenterons tout d’abord une modélisation complète du problème direct, depuis l’interaction onde-objet jusqu’à la propagation du champ jusqu’au détecteur, en intégrant absorption, réfraction et diffraction dans un cadre théorique unifié. Ces développements théoriques et numériques seront ensuite confrontés à des expériences réalisées sur synchrotron à l’ESRF ainsi que sur l’installation laser LULI2000, démontrant l’apport du formalisme ondulatoire pour l’étude de plasmas denses. Enfin, nous discuterons des perspectives envisagées sur des installations telles que le LMJ et les XFEL, ainsi que des pistes pour une résolution robuste et quantitative du problème inverse.
• High Entropy Alloy under Shock Compression: Optical-Pump X-Ray-Probe
  
  • Huang Hsin Hui
  • Ryu Meguya
  • Kamegaki Shuji
  • Stonyte Dominyka
  • Malinauskas Tadas
  • Nishijima Yoshiaki
  • Hocking Rosalie
  • Nguyen Hoai An Le
  • Katkus Tomas
  • Mu Haoran
  • Ng Soon Hock
  • Pinches Samuel
  • Ang Andrew S.M
  • Mizeikis Vygantas
  • Zatsepin Nadia
  • Miyanishi Kohei
  • Yabuuchi Toshinori
  • Nakamura Hirotaka
  • Amouretti Alexis
  • Ozaki Norimasa
  • Vinci Tommaso
  • Vailionis Arturas
  • Gamaly Eugene G
  • Hicks Damien G
  • Morikawa Junko
  • Juodkazis Saulius
  , 2026. High entropy alloys (HEAs) are multi-principal-element alloys designed for tailorable mechanical performance and have been attracting significant engineering interest, yet their fundamental behaviour under extreme dynamic conditions, such as shock loading, remains unexplored. Here, we report laser-shock experiments on two different types of 1-micrometers-thick HEA microfilms, CuPdAgPtAu and CrFeCoNiCuMo, on 25-micrometers-thick black-Kapton ablator driven by a high intensity laser pulse (532 nm, 5 ns, 16 J, 0.5-mm diameter focal spot) and probed by an X-ray free electron laser (XFEL) pulse (12 keV, 7 fs). Time-resolved X-ray diffraction (XRD) shows the formation of a transient phase with a lattice compression up to 5.1% of the CuPdAgPtAu HEA along the (111) plane; this transient compressed phase existed for 0.3 ns. The impedance matching Hugoniot analysis estimated a shock pressure of 55 +/- 6 GPa in the HEA film, while Au- and Fe-based equations of state (EoS) modelling predict 80 GPa (0.8 MBar) at the free HEA surface. The free HEA surface reached maximum velocities of ~ 5 km/s as recorded from in situ monitoring with the velocity interferometry system for any reflector (VISAR) imaging. These initial HEA results show the suitability of HEA sample preparation and XFEL-based XRD characterisation under extreme shock loading, and are promising for experimental determination of the EoS of this emerging class of materials (beamtime proposal No.: 2024A8503 for a 6-hour preliminary experiment).
• Gamma photon production and diagnostics in Laser-Plasma QED experiments
  
  • Nicotera Giuseppe
  , 2026. High-brilliance multi-MeV γ-ray sources play a central role in high-energy-density plasma physics and strong-field quantum electrodynamics (SF-QED). In this regime, intense light-matter interactions combine photon emission and pair creation, opening paths to study fundamental processes such as photon-photon scattering and to generate pair plasmas in the laboratory.This thesis develops an experimentally grounded framework connecting three stages: the production of high-energy γ photons in realistic multi-petawattlaser-plasma configurations, their spectral characterization, and their use to seed electromagnetic showersin matter. The numerical approach combines Particle-In-Cell (PIC) and Geant4 Monte Carlo simulations tomodel both laser-matter interactions and detector responses.The work first details the design and optimization of two compact magnetic spectrometers now operational at the Apollon facility: a Compton spectrometer(up to a few tens of MeV) and a pair spectrometer(broadband up to about 100 MeV). Then, PIC simulations of double-layer targets analyze how laser and target parameters influence γ emission, supporting recent experimental campaigns at Apollon.Finally, a semi-analytical modeling of showers in high-Z targets provides scaling laws for pair multiplicity and emergent spectra. Combining these concrete results with realistic beam parameters defines practical criteria to guide the generation of dense, quasi-neutral electron-positron pair jets in the multi-petawatt regime.
• Dual quantum locking: Dynamic coupling of H 2 and H 2 O sublattices in hydrogen-filled ice
  
  • Renaud Loan
  • Poreba Tomasz
  • Di Cataldo Simone
  • Nicholls Alasdair
  • Andriambariarijaona Léon
  • Rescigno Maria
  • Gaal Richard
  • Casula Michele
  • Saitta A. Marco
  • Eleonora Bove Livia
  Proceedings of the National Academy of Sciences of the United States of America, National Academy of Sciences, 2026, 123 (7), pp.e2526369123. Hydrogen hydrates (HH) are a unique class of materials composed of hydrogen molecules confined within crystalline water frameworks. Among their multiple phases, the filled ice structures, particularly the cubic C2 phase, exhibit exceptionally strong host–guest interactions due to ultra-short H 2 -H 2 O distances and a 1:1 stoichiometry leading to two interpenetrated identical diamond-like sublattices, one comprised of water molecules, the other of hydrogen molecules. At high pressures, nuclear-quantum effects involving both hydrogen molecules and the water lattice become dominant, giving rise to a dual-lattice quantum system. In this work, we explore the sequence of pressure- and temperature-driven phase transitions in HH, focusing on the interplay between molecular rotation, orientational ordering, lattice symmetry breaking, and hydrogen bond symmetrization. Using a combination of computational modeling based on classical and path-integral molecular dynamics, quantum embedding, and high pressure experiments, including Raman spectroscopy and synchrotron X-ray diffraction at low temperatures and high pressures, we identify signatures of quantum-induced ordering and structural transformations in the C2 phase. Our findings reveal that orientational ordering in HH occurs at much lower pressures than in solid hydrogen, by inducing structural changes in the water network and enhancing the coupling of water and hydrogen dynamics. This work provides insights into the quantum behavior of hydrogen under extreme mechanochemical confinement and establishes hydrogen-filled ices as a promising platform for the design of hydrogen-rich quantum materials. (10.1073/pnas.2526369123)
  DOI : 10.1073/pnas.2526369123
• Weibel-mediated filamentary structures observed in the ICF context
  
  • Ruyer C
  • Bolaños S
  • Laborde P.E. Masson
  • Gremillet L
  • Blanchot N
  • Boutoux G
  • Cayzac W
  • Courtois C
  • Dannhoff S.G
  • Denis V
  • Le Deroff L
  • Li C.K
  • Fuchs J
  • Grisollet A
  • Lantuéjoul I
  • Riquier R
  • Smets R
  • Sutcliffe G.D
  • Vauzour B
  Phys.Plasmas, 2026, 33 (5), pp.052113. In light of novel and past experimental results, we demonstrate how Weibel-mediated filamentary structures can develop in the expanding plasma plume of a laser-irradiated foil. The transverse ballistic cooling that occurs during the quasi-spherical plasma expansion naturally drives an electron pressure anisotropy, resulting in the growth of electron current filaments. This effect competes with electron-ion Coulomb collisions which tend to isotropize the electron distribution function. Based on theoretical and particle-in-cell modeling, we provide estimates of the dominant wavelength and amplitude of the self-generated magnetic fluctuations, which are found to explain experimental data obtained at the OMEGA and Laser Megajoule facilities. (10.1063/5.0321057)
  DOI : 10.1063/5.0321057
• Measuring the principle Hugoniot of low-density silica aerogel foam at pressures up to 160 GPa
  
  • Lee Jordan
  • Norreys Peter
  • Paddock Robert
  • Oliver Matthew
  • Ariyathilaka Pawala
  • Spindloe Christopher
  • Wyatt Donna
  • Irving Samuel
  • Fisher Ben
  • Woolsey Nigel
  • Bakandreas Stavros
  • Albertazzi Bruno
  • Koenig Michel
  • Rączka Piotr
  • Sano Takayoshi
  • Amouretti Alexis
  • Yamagata Naoki
  • Taketoshi Kai
  • Nishitani Kosuke
  • Ozaki Norimasa
  Physical Review E, American Physical Society (APS), 2026, 113 (5), pp.055210. Low-density foams are of significant interest in inertial confinement fusion (ICF), with potential applications as fuel carriers, ablation layers, or as a hohlraum filling material. Despite their potential, the shock response of these materials remains poorly characterized, limiting the accuracy of hydrodynamic simulations. Here we report experimental measurements of the equation of state for 90 mg/cm 3 silica ( SiO 2 ) aerogel foam under laser-driven shock compression, conducted at the GEKKO XII laser facility. Shock pressures between 50 and 160 GPa were achieved, and the corresponding states were determined using standard impedance-matching techniques with a quartz reference material. Initial measurements appeared to underestimate the foam shock velocity relative to predictions by the Quotidian Equation of State (QEOS) model. Experimental diagnostics indicated the presence of a vacuum gap between the reference material and the foam. The vacuum gaps were characterized, and one-dimensional radiation-hydrodynamic simulations were conducted to estimate their impact on the measured shock velocity. After applying simulation-based corrections, the experimental Hugoniot aligns closely with QEOS predictions, supporting the model's applicability to low-density foams. (10.1103/t226-ngw5)
  DOI : 10.1103/t226-ngw5
• Towards Laboratory Electron-Positron Plasma via Electromagnetic Showers in Matter
  
  • Pouyez M
  • Nicotera G
  • Galbiati M
  • Grismayer T
  • Lancia L
  • Riconda C
  • Grech M
  Commun.Phys., 2026, 9 (1), pp.21. The kinetic equations describing electromagnetic showers from high-energy electron beams interacting with targets are solved, building on the analytical framework developed in [Phys. Rev. Lett. 134, 135001 (2025)]. Two regimes are defined by the ratio of the target thickness L to the radiation length Lr , which depends on the electron energy and target composition. For thin targets (L < Lr ), we derive explicit expressions for the spectra of produced photons and pairs, as well as the number of pairs. For thick targets (L>Lr ), we obtain the total pair number and photon spectrum. Analytical results agree well with Geant4 simulations, which show that significant pair escape requires L<Lr . The divergence, density and characteristic dimensions of the escaping pair jets are obtained, and a criterion for pair plasma formation is derived. While current laser wakefield beams are not well adapted, multi-petawatt lasers may provide new electron or photon sources suitable for laboratory pair plasma production, opening new avenues for studying extreme plasma astrophysics in the laboratory. (10.1038/s42005-025-02449-8)
  DOI : 10.1038/s42005-025-02449-8
• Electron injection and acceleration into laser-driven wakefield from a solid overdense plasma target
  
  • Caetano de Sousa M.
  • Marini S.
  • Grech M.
  • Brunner S.
  • Riconda C.
  • Raynaud M.
  Physics of Plasmas, American Institute of Physics, 2026, 33 (8), pp.083103. A laser–plasma acceleration scheme combining electron extraction from a solid overdense target with wakefield acceleration in an adjacent underdense plasma region is presented. A laser pulse excites a diffracted electromagnetic wave at the overdense plasma interface, extracting and pre-accelerating electrons, which are then injected into laser-driven wakefield cavities in the underdense plasma. A parametric study identifies key conditions enabling efficient electron injection and energy gain in this two-stage acceleration configuration. Two-dimensional particle-in-cell simulations performed with the Smilei code show that the proposed scheme produces electron bunches with a tunable trade-off between charge, energy, and beam quality at laser intensity <i>I₀</i>λ$_0^2$ ≃ 3.4×10¹⁹ W μm²/cm² (λ₀ = 0.8 μm). According to the parameters used, the electron beam is accelerated to peak energies of ∼150−250 MeV with an estimated charge in 3D of ∼50−400 pC integrated over the full width at half maximum energy range, and ∼100−1900 pC with energies above 50 MeV. (10.1063/5.0346116)
  DOI : 10.1063/5.0346116
• Experimental investigation of the effect of ionization on the ⁵¹V(p,n)⁵¹Cr reaction
  
  • Lelasseux V.
  • Söderström P.-A.
  • Aogaki S.
  • Burdonov K.
  • Chen S.
  • Cvetinović A.
  • Dechefdebien E.
  • Dorard S.
  • Fazzini A.
  • Filippov E.
  • Gremillet L.
  • Gugiu M.
  • Horný V.
  • Lipoglavsek M.
  • Pikuz S.
  • Rotaru F.
  • Yao W.
  • Negoita F.
  • Fuchs J.
  Physics of Plasmas, American Institute of Physics, 2026, 33 (5), pp.053105. The investigation of the effects of atomic ionization on nuclear reactions is of prime importance for nuclear astrophysics. However, no direct experimental measurement of this effect using a plasma target could be done as of yet. In this regard, we measured for the first time the neutron yield of a (p,n) reaction taking place in a target having different states of ionization. The studied nuclear reaction in this work was ⁵¹V(p,n)⁵¹Cr, induced in a natural vanadium target exposed to an external, laser-driven proton beam. In the solid target case, we measured 91(26)% of the expected neutrons, but this rate dropped to 30(18)% when the target was ionized. This significant reduction remains unexplained, even after taking into account electron screening effects, the stopping power in the target, and target expansion. Our findings open new avenues for investigating how plasma ionization influences nuclear reactions in hot matter relevant for astrophysical environments. (10.1063/5.0310719)
  DOI : 10.1063/5.0310719
• Prospects for the production and detection of Breit-Wheeler tunneling positrons in Experiment 320 at the FACET-II accelerator
  
  • Borysov Oleksandr
  • Levi Alon
  • Meuren Sebastian
  • Nofech-Mozes Nathaly
  • Rajkovic Ivan
  • Reis David A
  • Santra Arka
  • Storey Doug W
  • Tal Hod Noam
  • Urmanov Roman
  Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Elsevier, 2026, 1083, pp.171144. The SLAC Experiment 320 collides 10 TW-class laser pulses with the high-quality, 10 GeV electron beam from the FACET-II RF LINAC. This setup is expected to produce a sizable number of $e^+e^-$ pairs via nonlinear Breit-Wheeler mechanism in the strong-field tunneling regime, with an estimated yield of ~0.01-0.1 pairs per collision. This small signal rate typically comes along with large backgrounds originating, e.g., from dumping the high-charge primary beam, secondaries induced by the beam halo, as well as photons and low-energy electrons produced in the electron-laser collision itself. These backgrounds may reach densities of O(100) charged particles per cm^2 (and even more neutral particles) at the surface of the sensing elements, making it a tremendous challenge for an unambiguous detection of single particles. In this work, we demonstrate how detectors and methods adapted from high-energy physics experiments, can enable this measurement. The solution presented is based on a highly granular, multi-layer, radiation-hard pixel detector paired with powerful particle-tracking algorithms. Using a detailed simulation of the existing experimental setup, we show how the false-positive rate due to background processes can be reduced by more than an order of magnitude relative to the expected signal after full reconstruction. Furthermore, we show that the high spatial tracking resolution achievable (<10 microns) allows for positron momentum measurements with a resolution of <2%, enabling spectral characterization of the nonlinear Breit-Wheeler process. Based on our extensive simulation, with a conservatively large background assumption, we show that it is possible to measure single Breit-Wheeler positrons in the coming data taking campaign of E320. That would be the first statistically significant observation and characterization of this elusive process in the (deep) tunneling regime. (10.1016/j.nima.2025.171144)
  DOI : 10.1016/j.nima.2025.171144