Publications

2024

• Digital laser and Coherent Beam combination
  
  • Ranély-Vergé-Dépré Claude-Alban
  , 2024. Coherent Beam Combining (CBC) is an innovative architectural approach to designing efficient laser sources combining high average power and high peak power (kW/GW), while offering great flexibility in the spatial shaping of the resulting beam. Ytterbium (Yb)-doped fiber amplifiers offer excellent thermal management thanks to the fiber's high surface-to-volume ratio (facilitating cooling) and high efficiency made possible by the long interaction lengths accessible and the low quantum defect of the Yb dopant. Moreover, these fibers feature a gain spectral width that supports pulse durations of down to a few hundred femtoseconds. This makes it possible to amplify femtosecond pulse trains at high repetition rates. The two prototypes studied in this thesis use the combination of this technology with CBC architecture. The first is based on a composite pupil with 61 tiled beams, offering individual control of its channels and introducing the concept of digital laser. Its pulse duration is reduced by a non-linear "post-compression" technique, enabling it to retain its digital properties. The second prototype, with its superposition of 7 pupils, is being studied and developed for its greater theoretical efficiency. (10.70675/78647ee8z1885z45a9z91cbz66c10246496a)
  DOI : 10.70675/78647ee8z1885z45a9z91cbz66c10246496a
• Localization in the quantum Hall effect : a magnetic localization approach
  
  • Seye Alioune
  , 2024. This thesis explores the localization properties of solutions to the disordered potential magnetic Schrödinger eigenvalue problem, modeling the quantum Hall effect (QHE) in the single-particle framework. Focusing on the first Landau level, we compare numerically computed eigenstates to predictions derived from the Magnetic Localization Landscape (MLL).Localization plays a pivotal role in the Integer Quantum Hall Effect (IQHE), where strong magnetic fields enable semiclassical simplifications for estimating energy and current, providing insight into plateau transitions. However, our understanding of localization beyond the large magnetic field regime remains incomplete. To address this, we introduce the localization landscape (LL) theory and its magnetic extension, the MLL, which incorporates magnetic effects into the deterministic framework of the LL, enabling a new perspective on localization in disordered magnetic systems.Using a gauge-invariant finite element method, we solve the magnetic Schrödinger eigenvalue problem numerically and analyze the localization properties of the eigenstates. The MLL offers an effective potential that can be interpreted semiclassically in regimes where magnetic intensity and disorder strength are comparable. Eigenstates localize on the wells and hills of this effective potential, with their energies closely matching the effective potential values at points of maximal probability density. Moreover, the MLL-based Agmon distance provides a reliable estimate of the exponential decay for low-energy eigenstates.Our findings suggest that the MLL effectively describes the potential seen by the center of orbit associated to eigenstates, offering a simplified yet insightful model to describe localization of such magnetic disordered systems. (10.70675/e25b1ea0z302bz4b26z8362ze22d0a879c3a)
  DOI : 10.70675/e25b1ea0z302bz4b26z8362ze22d0a879c3a
• High fidelity phase conjugation in a stimulated Brillouin scattering cell at 122 J
  
  • Humblot Raphaël
  • Stéphane Branly
  • Loïc Meignien
  • Patrick Audebert
  • Frédéric Druon
  Optics Express, Optical Society of America - OSA Publishing, 2024, 32 (26), pp.47347-47359. We demonstrate a passive and automatic correction of high-energy laser wavefront using stimulated Brillouin scattering (SBS) based phase conjugating mirror (PCM) establishing a new record in terms of input energy level of 122 J together with an extremely high reflectivity, leading to efficiencies of 99 % with both high temporal fidelity and good spatial profile conservation. For this achievement, we developed an innovative design of high-energy SBS-PCM based on high numerical aperture focusing and on the temporal shaping of the input pulse, guaranteeing good SBS initiation before the arrival of the main part of the pulse. An original approach was introduced compared to previous works where the temporal fidelity was a limitation for energy scale-up. This approach allows, for the first time in an SBS cell, perfect conservation of the input pulse temporal profile, demonstrated for several temporal pulse shapes of interest. Pulsed laser sources with nanosecond duration and energy levels above the kilojoule represent a crucial tool for a wide range of plasma and shock physics experiments. This work will unlock a crucial bottleneck by addressing the correction of the wavefront distortions due to the accumulating thermal load in these lasers and opens the way to higher repetition rate kilojoule systems. (10.1364/oe.538542)
  DOI : 10.1364/oe.538542
• The Mysterious Interior of Uranus: Final Report of the 2023 KISS Study
  
  • Hofstadter Mark
  • Helled Ravit
  • Stevenson David J.
  • Ehlmann Bethany
  • Bethkenhagen Mandy
  • Cao Hao
  • Dong Junjie
  • Moutamid Maryame El
  • Ermakov Anton
  • Fuller Jim
  • Guillot Tristan
  • Idini Benjamin
  • Izidoro Andre
  • Kaspi Yohai
  • Kovacevic Tanja
  • Lainey Valéry
  • Levin Steve
  • Lunine Jonathan
  • Mankovich Christopher
  • Markham Stephen
  • Millot Marius
  • Mousis Olivier
  • Müller Simon
  • Nettelmann Nadine
  • Nimmo Francis
  • Parisi Marzia
  • Soderland Krista
  • Stixrude Lars
  • Teanby Nick
  • Vazan Allona
  , 2024. Determining the internal structure of Uranus is a key objective for planetary science. Knowledge of Uranus’s bulk composition and the distribution of elements is crucial to understanding its origin and evolutionary path. In addition, Uranus represents a poorly understood class of “intermediate-mass planets” (intermediate in size between the relatively well studied terrestrial and gas giant planets), which appear to be very common in the Galaxy. As a result, a better characterization of Uranus will also help us to better understand exoplanets in this mass and size regime. Recognizing the importance of Uranus, a Keck Institute for Space Studies (KISS) workshop was held in September 2023 to investigate how we can improve our knowledge of Uranus’s internal structure in the context of a future Uranus mission that includes an orbiter and a probe. The scientific goals and objectives of the recently released Planetary Science and Astrobiology Decadal Survey were taken as our starting point. We reviewed our current knowledge of Uranus’s interior and identified measurement and other mission requirements for a future Uranus spacecraft, providing more detail than was possible in the Decadal Survey’s mission study and including new insights into the measurements to be made. We also identified importantknowledge gaps to be closed with Earth-based efforts in the near term that will help guide the design of the mission and interpret the data returned. Our report focuses on the following topics:• Uranus’s atmosphere (noble gas, elemental, and molecular abundances and the pressure-temperature profile)• Its gravity field and interior models• The planet’s magnetic field, heat flux, and energy balance• The potential for Uranian seismology In the words of the Decadal Survey, the Uranus Flagship mission can produce “transformative, breakthrough science across a broad range of topics.” We argue that to fulfill its promise, great progress should be made in terms of mission design, theoretical calculations, numerical modeling, experiments, ground-based observations, and bringing communities together to plan the mission and interpret the data it returns. (10.7907/1k6kh-fjs61)
  DOI : 10.7907/1k6kh-fjs61
• A comprehensive characterization of the neutron fields produced by the Apollon petawatt laser
  
  • Lelièvre Ronan
  • Yao Weipeng
  • Waltenspiel Tessa
  • Cohen Itamar
  • Anthonippillai Viviange
  • Antici Patrizio
  • Beck Arie
  • Cohen Erez
  • Michaeli David
  • Pomerantz Ishay
  • Gautier Donald Cort
  • Trompier François
  • Ducasse Quentin
  • Koseoglou Pavlos
  • Söderström Pär-Anders
  • Mathieu François
  • Allaoua Amokrane
  • Fuchs Julien
  The European Physical Journal Plus, Springer, 2024, 139 (11), pp.1035. Since two decades, laser-driven neutron emissions are studied as they represent a complementary source to conventional neutron sources, with further more different characteristics (i.e. shorter bunch duration and higher number of neutrons per bunch). We report here a global, thorough characterization of the neutron fields produced at the Apollon laser facility using the secondary laser beam (F2). A Double Plasma Mirror (DPM) was used to improve the temporal contrast of the laser which delivers pulses of 24 fs duration, a mean on-target energy of ~10 J and up to 1 shot/min. The interaction of the laser with thin targets (few tens or hundreds of nm) in ultra-high conditions produced enhanced proton beams (up to 35 MeV), which were then used to generate neutrons via the pitcher-catcher technique. The characterization of these neutron emissions is presented, with results obtained from both simulations and measurements using several diagnostics (activation samples, bubble detectors and Time-of-Flight detectors), leading to a neutron yield of ~4.10$^7$ neutrons/shot. Similar neutron emissions were observed during shots with and without DPM, while fewer X-rays are produced when the DPM is used, making this tool interesting to adjust the neutrons/X-rays ratio for some applications like combined neutron/X-ray radiography. (10.1140/epjp/s13360-024-05679-x)
  DOI : 10.1140/epjp/s13360-024-05679-x
• Growth rate of self-sustained QED cascades induced by intense lasers
  
  • Mercuri-Baron A.
  • Mironov A.
  • Riconda C.
  • Grassi A.
  • Grech M.
  , 2024. It was suggested [A. R. Bell & J. G. Kirk, PRL 101, 200403 (2008)] that an avalanche of electron-positron pairs can be triggered in the laboratory by a standing wave generated by intense laser fields. Here, we present a general solution to the long-standing problem of the avalanche growth rate calculation. We provide a simple formula that accounts for the damping of the growth rate due to pair and photon migration from the region of prolific generation. We apply our model to a variety of 3D field configurations including focused laser beams and show that i) the particle yield for the full range of intensity able to generate an avalanche can be predicted, ii) a critical intensity threshold due to migration is identified, iii) the effect of migration is negligible at a higher intensity and the local growth rate dominates. Excellent agreement with Monte Carlo and self-consistent PIC simulations is shown. The growth rate calculation allows us to predict when abundant pair production will induce a back-reaction on the generating field due to plasma collective effects and screening. Our model can be applied to study the generation of electron-positron pair avalanches in realistic fields to plan future experiments at ultra-high-intensity laser facilities. (10.48550/arXiv.2402.04225)
  DOI : 10.48550/arXiv.2402.04225
• Characterization of laser-driven neutron emissions
  
  • Lelievre Ronan
  , 2024. Ultra-intense lasers represent a new way to produce neutron fields, more compact than nuclear reactors or accelerators and with fewer radiological constraints than these conventional sources. The electric field induced by an ultra-intense laser pulse within a micrometer-sized target can reach several TV/m, allowing for the acceleration of protons to several tens of MeV. These protons can then be intercepted by a second target, called a converter, in which they induce nuclear reactions and thus produce neutrons. This technique, known as the pitcher-catcher technique, is capable of generating very intense fluxes (> 10^17 n/cm²/s) at energies up to several tens of MeV, making it possible to envision applications such as neutron imaging or the laboratory reproduction of the rapid nucleosynthesis process responsible for the creation of the heaviest elements.To demonstrate the feasibility of these applications and ensure the radiological protection of these laser facilities, these neutron fields must be optimally characterized. Detectors with ultra-fast electronics or passive detectors appear to be most compatible to the characteristics of laser-driven neutron sources (very brief and intense emissions, noisy environment, etc.).This thesis work focuses on optimizing the development of a neutron activation spectrometer (SPAC), particularly suitable for measuring intense neutron fields with a strong gamma component. In addition to simulations of the expected source terms and detector responses using Geant4 & MCNP Monte Carlo codes, bubble dosimeters, Time-of-Flight detectors and activation samples were used on various laser facilities such as ALLS (Canada) and Apollon (France), to optimize and characterize the produced neutron emissions. (10.70675/e5145877zc9b1z42d0zb6eez1c3224167408)
  DOI : 10.70675/e5145877zc9b1z42d0zb6eez1c3224167408
• Shock-driven amorphization and melt in Fe$_2$O$_3$
  
  • Crépisson Céline
  • Amouretti Alexis
  • Harmand Marion
  • Sanloup Chrystèle
  • Heighway Patrick
  • Azadi Sam
  • Mcgonegle David
  • Campbell Thomas
  • Chin David Alexander
  • Smith Ethan
  • Hansen Linda
  • Forte Alessandro
  • Gawne Thomas
  • Lee Hae Ja
  • Nagler Bob
  • Shi Yuanfeng
  • Fiquet Guillaume
  • Guyot François
  • Makita Mikako
  • Benuzzi-Mounaix Alessandra
  • Vinci Tommaso
  • Miyanishi Kohei
  • Ozaki Norimasa
  • Pikuz Tatiana
  • Nakamura Hirotaka
  • Sueda Keiichi
  • Yabuuchi Toshinori
  • Yabashi Makina
  • Wark Justin
  • Polsin Danae
  • Vinko Sam
  , 2024. We present measurements on Fe$_2$O$_3$ amorphization and melt under laser-driven shock compression up to 209(10) GPa via time-resolved in situ x-ray diffraction. At 122(3) GPa, a diffuse signal is observed indicating the presence of a non-crystalline phase. Structure factors have been extracted up to 182(6) GPa showing the presence of two well-defined peaks. A rapid change in the intensity ratio of the two peaks is identified between 145(10) and 151(10) GPa, indicative of a phase change. Present DFT+$U$ calculations of temperatures along Fe$_2$O$_3$ Hugoniot are in agreement with SESAME 7440 and indicate relatively low temperatures, below 2000 K, up to 150 GPa. The non-crystalline diffuse scattering is thus consistent with the - as yet unreported - shock amorphization of Fe$_2$O$_3$ between 122(3) and 145(10) GPa, followed by an amorphous-to-liquid transition above 151(10) GPa. Upon release, a non-crystalline phase is observed alongside crystalline $α$-Fe$_2$O$_3$. The extracted structure factor and pair distribution function of this release phase resemble those reported for Fe$_2$O$_3$ melt at ambient pressure. (10.48550/arXiv.2408.17204)
  DOI : 10.48550/arXiv.2408.17204
• Saturation of the compression of two interacting magnetized plasma toroids evidenced in the laboratory
  
  • Sladkov A.
  • Fegan C.
  • Yao W.
  • Bott A F A
  • Chen S N
  • Ahmed H.
  • Filippov E D
  • Lelièvre R.
  • Martin P.
  • Mcilvenny A.
  • Waltenspiel T.
  • Antici P.
  • Borghesi M.
  • Pikuz S.
  • Ciardi A.
  • D’humières E.
  • Soloviev A.
  • Starodubtsev M.
  • Fuchs J.
  Nature Communications, Nature Publishing Group, 2024, 15 (1), pp.10065. Interactions between magnetic fields advected by matter play a fundamental role in the Universe at a diverse range of scales. A crucial role these interactions play is in making turbulent fields highly anisotropic, leading to observed ordered fields. These in turn, are important evolutionary factors for all the systems within and around. Despite scant evidence, due to the difficulty in measuring even near-Earth events, the magnetic field compression factor in these interactions, measured at very varied scales, is limited to a few. However, compressing matter in which a magnetic field is embedded, results in compression up to several thousands. Here we show, using laboratory experiments and matching three-dimensional hybrid simulations, that there is indeed a very effective saturation of the compression when two independent parallel-oriented magnetic fields regions encounter one another due to plasma advection. We found that the observed saturation is linked to a build-up of the magnetic pressure, which decelerates and redirects the inflows at their encounter point, thereby stopping further compression. Moreover, the growth of an electric field, induced by the incoming flows and the magnetic field, acts in redirecting the inflows transversely, further hampering field compression. (10.1038/s41467-024-53938-3)
  DOI : 10.1038/s41467-024-53938-3
• Tailoring coherent beam combined laser pulse trains for high peak and average power applications
  
  • Ranély-Vergé-Dépré Claude-Alban
  • Lechevalier Corentin
  • Andrieu Jordan
  • Fsaifes Ihsan
  • Jovanovic Igor
  • Chanteloup Jean-Christophe
  High Power Laser Science and Engineering, Cambridge University Press, 2024, 12, pp.e93. Laser systems based on coherent beam combination (CBC) that rely on tiled pupil architecture intrinsically carry digital capabilities independently applicable to all three essential characteristics of a laser pulse: amplitude, phase and polarization. Those capabilities allow the far-field energy distribution to be flexibly tailored in real time. Operation in the femtosecond regime at high repetition rates gives access to a wide range of applications requiring both high peak and average powers. We address the task of independent peak versus average power adjustment needed for applications seeking to decouple nonlinear phenomena associated with GW peak power from the thermal load inherent to kW average power operation. The technical solutions proposed are presented in the framework of the Ecole Polytechnique XCAN CBC laser platform (61 independent channels) with an emphasis on thermal management measures implemented to ensure its nominal operation. (10.1017/hpl.2024.77)
  DOI : 10.1017/hpl.2024.77
• Overview and progress on the XCAN digital laser
  
  • Lechevalier Corentin
  • Andrieu Jordan
  • Ranély-Vergé-Dépré Claude-Alban
  • Fsaifes Ihsan
  • Boer Gerben
  • Chanteloup Jean-Christophe
  , 2024, pp.ATh1A.5. <div><p>We present recent progress achieved on XCAN coherent beam combining laser, enabling versatile capabilities such as on-demand far-field energy distribution, polarization control, and access to several pulse durations, while operating in a digital mode.</p></div> (10.1364/ASSL.2024.ATh1A.5)
  DOI : 10.1364/ASSL.2024.ATh1A.5
• First principles simulations of dense hydrogen
  
  • Bonitz Michael
  • Vorberger Jan
  • Bethkenhagen Mandy
  • Böhme Maximilian
  • Ceperley David
  • Filinov Alexey
  • Gawne Thomas
  • Graziani Frank
  • Gregori Gianluca
  • Hamann Paul
  • Hansen Stephanie
  • Holzmann Markus
  • Hu S.
  • Kählert Hanno
  • Karasiev Valentin
  • Kleinschmidt Uwe
  • Kordts Linda
  • Makait Christopher
  • Militzer Burkhard
  • Moldabekov Zhandos
  • Pierleoni Carlo
  • Preising Martin
  • Ramakrishna Kushal
  • Redmer Ronald
  • Schwalbe Sebastian
  • Svensson Pontus
  • Dornheim Tobias
  , 2024. Accurate knowledge of the properties of hydrogen at high compression is crucial for astrophysics (e.g. planetary and stellar interiors, brown dwarfs, atmosphere of compact stars) and laboratory experiments, including inertial confinement fusion. There exists experimental data for the equation of state, conductivity, and Thomson scattering spectra. However, the analysis of the measurements at extreme pressures and temperatures typically involves additional model assumptions, which makes it difficult to assess the accuracy of the experimental data. rigorously. On the other hand, theory and modeling have produced extensive collections of data. They originate from a very large variety of models and simulations including path integral Monte Carlo (PIMC) simulations, density functional theory (DFT), chemical models, machine-learned models, and combinations thereof. At the same time, each of these methods has fundamental limitations (fermion sign problem in PIMC, approximate exchange-correlation functionals of DFT, inconsistent interaction energy contributions in chemical models, etc.), so for some parameter ranges accurate predictions are difficult. Recently, a number of breakthroughs in first principle PIMC and DFT simulations were achieved which are discussed in this review. Here we use these results to benchmark different simulation methods. We present an update of the hydrogen phase diagram at high pressures, the expected phase transitions, and thermodynamic properties including the equation of state and momentum distribution. Furthermore, we discuss available dynamic results for warm dense hydrogen, including the conductivity, dynamic structure factor, plasmon dispersion, imaginary-time structure, and density response functions. We conclude by outlining strategies to combine different simulations to achieve accurate theoretical predictions. (10.48550/arXiv.2405.10627)
  DOI : 10.48550/arXiv.2405.10627
• Spall fracture in wrought and additively manufactured Ni-based superalloys subjected to high pressure laser-driven shocks
  
  • Barraud Etienne
  • de Rességuier Thibaut
  • Hémery Samuel
  • Cormier Jonathan
  • Vinci Tommaso
  • Benuzzi-Mounaix Alessandra
  • Raffray Yoann
  • Loison Didier
  Materials Science and Engineering: A, Elsevier, 2024, 911, pp.146944. The impact response of Nickel-based superalloys is still poorly documented with respect to the industrial interest in these materials. Here, laser-driven shocks are used to study and compare the dynamic behavior of Rene 65 superalloy with different microstructures at very high strain rates in the order of 106 s−1. Rene 65 specimens studied here are either in cast and wrought or additively manufactured (laser powder bed fusion) and subjected to different heat treatment conditions. Time-resolved velocity measurements provide the yield strength (Hugoniot elastic limit) and spall strength (resistance to dynamic tension) of each variant. In addition, post-recovery characterization gives insight into the initiation and propagation of dynamic fracture, which are shown to depend on the different manufacturing routes and thermal histories. (10.1016/j.msea.2024.146944)
  DOI : 10.1016/j.msea.2024.146944
• High repetition-rate 0.5 Hz broadband neutron source driven by the Advanced Laser Light Source
  
  • Lelievre Ronan
  • Catrix E.
  • Vallières S.
  • Fourmaux S.
  • Allaoua Amokrane
  • Anthonippillai V.
  • Antici P.
  • Ducasse Quentin
  • Fuchs J.
  Physics of Plasmas, American Institute of Physics, 2024, 31 (9), pp.093106. Neutron beams are an essential tool to investigate material structure and perform nondestructive analysis, as they give unique access to element composition, thus ideally complementing density analysis allowed by standard x-rays investigation. Laser-driven neutron sources, though compact and cost-effective, currently have lower average flux than conventional neutron sources, due to the limited repetition rate of the lasers used so far. However, advancements in laser technology allow nowadays to address this challenge. Here, we report results obtained at the Advanced Laser Light Source characterizing stable production of broadband (0.1–2 MeV) neutrons produced at a high repetition rate (0.5 Hz). The interaction of laser pulses of 22 fs duration and 3.2 J on-target energy with 2-μm-thick tantalum targets produced protons in the Target Normal Sheath Acceleration (TNSA) regime up to 7.3 MeV. These protons were subsequently converted into neutrons by (p,n) reactions in lithium fluoride (LiF). Activation measurements and bubble detectors were used to characterize neutron emissions, with a neutron fluence of up to ∼1.4×105 neutrons/shot/sr and energies mainly between a few hundred of kilo-electron volt and 2 MeV. The total neutron yield was ∼5×105 neutrons/shot. This paves the way for numerous applications, e.g., in homeland security, materials science, or cultural heritage. (10.1063/5.0218582)
  DOI : 10.1063/5.0218582
• Photochemically induced acousto-optics in gases
  
  • Michel P.
  • Lancia L.
  • Oudin A.
  • Kur E.
  • Riconda C.
  • Ou K.
  • Perez-Ramirez V.M.
  • Lee J.
  • Edwards M.R.
  Physical Review Applied, American Physical Society, 2024, 22 (2), pp.024014. Acousto-optics consists of launching acoustic waves in a medium (usually a crystal) in order to modulate its refractive index and create a tunable optical grating. In this article, we present the theoretical basis of a new scheme to generate acousto-optics in a gas, where the acoustic waves are initiated by the localized absorption (and thus gas heating) of spatially-modulated UV light, as was demonstrated in Y. Michine and H. Yoneda, Commun. Phys. 3, 24 (2020). We identify the chemical reactions initiated by the absorption of UV light via the photodissociation of ozone molecules present in the gas, and calculate the resulting temperature increase in the gas as a function of space and time. Solving the Euler fluid equations shows that the modulated, isochoric heating initiates a mixed acoustic/entropy wave in the gas, whose high-amplitude density (and thus refractive index) modulation can be used to manipulate a high-power laser. We calculate that diffraction efficiencies near 100% can be obtained using only a few millimeters of gas containing a few percent ozone fraction at room temperature, with UV fluences of less than 100 mJ/cm 2 -consistent with the experimental measurements. Our analysis suggests possible ways to optimize the diffraction efficiency by changing the buffer gas composition. Gases have optics damage thresholds two to three times beyond those of solids; these optical elements should therefore be able to manipulate kJ-class lasers. (10.1103/PhysRevApplied.22.024014)
  DOI : 10.1103/PhysRevApplied.22.024014
• Enhanced energy, conversion efficiency and collimation of protons driven by high-contrast and ultrashort laser pulses
  
  • Yao Weipeng
  • Lelièvre Ronan
  • Waltenspiel Tessa
  • Cohen Itamar
  • Allaoua Amokrane
  • Antici Patrizio
  • Beck Arie
  • Cohen Erez
  • Davoine Xavier
  • D’humières Emmanuel
  • Ducasse Quentin
  • Filippov Evgeny
  • Gautier Cort
  • Gremillet Laurent
  • Koseoglou Pavlos
  • Michaeli David
  • Papadopoulos Dimitrios
  • Pikuz Sergey
  • Pomerantz Ishay
  • Trompier Francois
  • Yuan Yuran
  • Mathieu Francois
  • Fuchs Julien
  Applied Sciences, Multidisciplinary digital publishing institute (MDPI), 2024, 14 (14), pp.6101. Progress in laser-driven proton acceleration requires increasing the proton maximum energy and laser-to-proton conversion efficiency while reducing the divergence of the proton beam. However, achieving all these qualities simultaneously has proven challenging experimentally, with the increase in beam energy often coming at the cost of beam quality. Numerical simulations suggest that coupling multi-PW laser pulses with ultrathin foils could offer a route for such simultaneous improvement. Yet, experimental investigations have been limited by the scarcity of such lasers and the need for very stringent temporal contrast conditions to prevent premature target expansion before the pulse maximum. Here, combining the newly commissioned Apollon laser facility that delivers high-power ultrashort (∼24 fs) pulses with a double plasma mirror scheme to enhance its temporal contrast, we demonstrate the generation of up to 35 MeV protons with only 5 J of laser energy. This approach also achieves improved laser-to-proton energy conversion efficiency, reduced beam divergence, and optimized spatial beam profile. Therefore, despite the laser energy losses induced by the plasma mirror, the proton beams produced by this method are enhanced on all accounts compared to those obtained under standard conditions. Particle-in-cell simulations reveal that this improvement mainly results from a better space-time synchronization of the maximum of the accelerating charge-separation field with the proton bunch. (10.3390/app14146101)
  DOI : 10.3390/app14146101
• Demonstrating grating-based phase-contrast imaging of laser-driven shock waves
  
  • Wegert Leonard
  • Schreiner Stephan
  • Rauch Constantin
  • Albertazzi Bruno
  • Bleuel Paulina
  • Fröjdh Eric
  • Koenig Michel
  • Ludwig Veronika
  • Martynenko Artem
  • Meyer Pascal
  • Mozzanica Aldo
  • Müller Michael
  • Neumayer Paul
  • Schneider Markus
  • Triantafyllidis Angelos
  • Zielbauer Bernhard
  • Anton Gisela
  • Michel Thilo
  • Funk Stefan
  Matter and Radiation at Extremes, AIP Publishing, 2024, 9 (4). Single-shot X-ray phase-contrast imaging is used to take high-resolution images of laser-driven strong shock waves. Employing a two-grating Talbot interferometer, we successfully acquire standard absorption, differential phase-contrast, and dark-field images of the shocked target. Good agreement is demonstrated between experimental data and the results of two-dimensional radiation hydrodynamics simulations of the laser–plasma interaction. The main sources of image noise are identified through a thorough assessment of the interferometer’s performance. The acquired images demonstrate that grating-based phase-contrast imaging is a powerful diagnostic tool for high-energy-density science. In addition, we make a novel attempt at using the dark-field image as a signal modality of Talbot interferometry to identify the microstructure of a foam target. (10.1063/5.0200440)
  DOI : 10.1063/5.0200440
• Photon emission and radiation reaction effects in surface plasma waves in ultra-high intensities
  
  • Kleij P.
  • Marini S.
  • Caetano de Sousa M.
  • Grech M.
  • Riconda C.
  • Raynaud M.
  Physics of Plasmas, American Institute of Physics, 2024, 31 (7). Manipulating and harnessing plasmonic phenomena in the ultra-relativistic regime reveal promising prospects for the use of surface plasma waves (SPW) to create high-energy particle and radiation sources in the next generation of multi-petawatt lasers. Indeed, relativistic high-charge electron bunches can be produced by SPW excited by ultra-high intensity femtosecond lasers impinging on a periodically modulated solid-density target. In this regime, there is good evidence that SPW excitation survives and that the produced electron bunches experience strong acceleration, thus emitting large amounts of electromagnetic radiation. Therefore, extending the study to ultra-high laser intensities (I&gt;1021 W/cm2), the use of a resonant grating for SPW generation represents an interesting alternative to light sources, as the energy lost by electrons due to radiation emission is transferred to high-energy γ photons. In addition, we show that using a laser with wavefront rotation coupled with a tailored blazed grating improves photon emission in the ultra-relativistic regime of interaction. (10.1063/5.0209316)
  DOI : 10.1063/5.0209316
• Optimizing laser coupling, matter heating, and particle acceleration from solids using multiplexed ultraintense lasers
  
  • Yao Weipeng
  • Nakatsutsumi Motoaki
  • Buffechoux Sébastien
  • Antici Patrizio
  • Borghesi Marco
  • Ciardi Andrea
  • Chen Sophia
  • D’humières Emmanuel
  • Gremillet Laurent
  • Heathcote Robert
  • Horný Vojtěch
  • Mckenna Paul
  • Quinn Mark
  • Romagnani Lorenzo
  • Royle Ryan
  • Sarri Gianluca
  • Sentoku Yasuhiko
  • Schlenvoigt Hans-Peter
  • Toncian Toma
  • Tresca Olivier
  • Vassura Laura
  • Willi Oswald
  • Fuchs Julien
  Matter and Radiation at Extremes, AIP Publishing, 2024, 9 (4). 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. (10.1063/5.0184919)
  DOI : 10.1063/5.0184919
• A "lighthouse" laser-driven staged proton accelerator allowing for ultrafast angular and spectral control
  
  • Horný Vojtěch
  • Burdonov Konstantin
  • Fazzini Alice
  • Lelasseux Vincent
  • Antici Patrizio
  • Chen Sophia Nan
  • Ciardi Andrea
  • Davoine Xavier
  • d'Humières Emmanuel
  • Gremillet Laurent
  • Lecherbourg Ludovic
  • Mathieu François
  • Papadopoulos Dimitrios
  • Yao Weipeng
  • Fuchs Julien
  , 2024. Compact laser-plasma acceleration of fast ions has made great strides since its discovery over two decades ago, resulting in the current generation of high-energy ($\geq 100\,\rm MeV$) ultracold beams over ultrashort ($\leq 1\,\rm ps$) durations. To unlock broader applications of these beams, we need the ability to tailor the ion energy spectrum. Here, we present a scheme that achieves precisely this by accelerating protons in a "lighthouse" fashion, whereby the highest-energy component of the beam is emitted in a narrow cone, well separated from the lower-energy components. This is made possible by a two-stage interaction in which the rear surface of the target is first set into rapid motion before the main acceleration phase. This approach offers the additional advantages of leveraging a robust sheath acceleration process in standard micron-thick targets and being optically controllable.
• In-situ metrology interferometric set-up for the diagnosis and analysis of coherent beam combining lasers
  
  • Rousseaux Thomas
  • Primot Jérôme
  • Rouzé Bastien
  • Chanteloup Jean-Christophe
  • Bellanger Cindy
  , 2024, pp.JTu2A.15. We present a new compact Pistil interferometer, specifically d esigned for easy integration on all CBC lasers. This demonstrator enables self-referenced and accu-rate measurements of the near-field phase, whatever the set-point applied. (10.1364/CLEO_AT.2024.JTu2A.15)
  DOI : 10.1364/CLEO_AT.2024.JTu2A.15
• Optimization of laser-driven quantum beam generation and the applications with artificial intelligence
  
  • Kuramitsu Y.
  • Taguchi T.
  • Nikaido F.
  • Minami T.
  • Hihara T.
  • Suzuki S.
  • Oda K.
  • Kuramoto K.
  • Yasui T.
  • Abe Y.
  • Ibano K.
  • Takabe H.
  • Chu C.
  • Wu K.
  • Woon W.
  • Chen S.
  • Jao C.
  • Chen Y.
  • Liu Y.
  • Morace A.
  • Yogo A.
  • Arikawa Y.
  • Kohri H.
  • Tokiyasu A.
  • Kodaira S.
  • Kusumoto T.
  • Kanasaki M.
  • Asai T.
  • Fukuda Y.
  • Kondo K.
  • Kiriyama H.
  • Hayakawa T.
  • Tanaka S.
  • Isayama S.
  • Watamura N.
  • Suzuki H.
  • Kumar H.
  • Ohnishi N.
  • Pikuz T.
  • Filippov E.
  • Sakai K.
  • Yasuhara R.
  • Nakata M.
  • Ishikawa R.
  • Hoshi T.
  • Mizuta A.
  • Bolouki N.
  • Saura N.
  • Benkadda Sadruddin
  • Koenig M.
  • Hamaguchi S.
  Physics of Plasmas, American Institute of Physics, 2024, 31 (5), pp.053108. We have investigated space and astrophysical phenomena in nonrelativistic laboratory plasmas with long high-power lasers, such as collisionless shocks and magnetic reconnections, and have been exploring relativistic regimes with intense short pulse lasers, such as energetic ion acceleration using large-area suspended graphene. Increasing the intensity and repetition rate of the intense lasers, we have to handle large amounts of data from the experiments as well as the control parameters of laser beamlines. Artificial intelligence (AI) such as machine learning and neural networks may play essential roles in optimizing the laser and target conditions for efficient laser ion acceleration. Implementing AI into the laser system in mind, as the first step, we are introducing machine learning in ion etch pit analyses detected on plastic nuclear track detectors. Convolutional neural networks allow us to analyze big ion etch pit data with high precision and recall. We introduce one of the applications of laser-driven ion beams using AI to reconstruct vector electric and magnetic fields in laser-produced turbulent plasmas in three dimensions. (10.1063/5.0190062)
  DOI : 10.1063/5.0190062
• Review of the second charged-particle transport coefficient code comparison workshop
  
  • Stanek Lucas
  • Kononov Alina
  • Hansen Stephanie
  • Haines Brian
  • Hu S.
  • Knapp Patrick
  • Murillo Michael
  • Stanton Liam
  • Whitley Heather
  • Baalrud Scott
  • Babati Lucas
  • Baczewski Andrew
  • Bethkenhagen Mandy
  • Blanchet Augustin
  • Clay Raymond
  • Cochrane Kyle
  • Collins Lee
  • Dumi Amanda
  • Faussurier Gerald
  • French Martin
  • Johnson Zachary
  • Karasiev Valentin
  • Kumar Shashikant
  • Lentz Meghan
  • Melton Cody
  • Nichols Katarina
  • Petrov George
  • Recoules Vanina
  • Redmer Ronald
  • Röpke Gerd
  • Schörner Maximilian
  • Shaffer Nathaniel
  • Sharma Vidushi
  • Silvestri Luciano
  • Soubiran François
  • Suryanarayana Phanish
  • Tacu Mikael
  • Townsend Joshua
  • White Alexander
  Physics of Plasmas, American Institute of Physics, 2024, 31 (5). We report the results of the second charged-particle transport coefficient code comparison workshop, which was held in Livermore, California on 24–27 July 2023. This workshop gathered theoretical, computational, and experimental scientists to assess the state of computational and experimental techniques for understanding charged-particle transport coefficients relevant to high-energy-density plasma science. Data for electronic and ionic transport coefficients, namely, the direct current electrical conductivity, electron thermal conductivity, ion shear viscosity, and ion thermal conductivity were computed and compared for multiple plasma conditions. Additional comparisons were carried out for electron–ion properties such as the electron–ion equilibration time and alpha particle stopping power. Overall, 39 participants submitted calculated results from 18 independent approaches, spanning methods from parameterized semi-empirical models to time-dependent density functional theory. In the cases studied here, we find significant differences—several orders of magnitude—between approaches, particularly at lower temperatures, and smaller differences—roughly a factor of five—among first-principles models. We investigate the origins of these differences through comparisons of underlying predictions of ionic and electronic structure. The results of this workshop help to identify plasma conditions where computationally inexpensive approaches are accurate, where computationally expensive models are required, and where experimental measurements will have high impact. (10.1063/5.0198155)
  DOI : 10.1063/5.0198155
• From the Nascent Earth to Ante-Cells Molecular Structures?
  
  • T Michel
  Journal of Biomedical Research & Environmental Sciences, SciRes Literature LLC, 2024, 5 (5), pp.440-444. During its early youth, the Earth was the site of extremely violent processes. In particular, the energy of the impact of the planet Theia with the young Earth was such that the latter became entirely covered with a thick layer of molten magma, called the "magma ocean". On the now calmed Earth that we currently know, the objects classified as "living" by our sense organs are distinguished from those classified as "non-living" by two main characteristics: i) living objects have a completely original organic molecular constitution and ii) in contrast to non-living objects, which tend to equilibrate with the outside, living objects never reach equilibrium and are therefore "obligatory dynamical systems" out of equilibrium. It seems that the dynamic characteristic was acquired before the molecular characteristic for the genesis on Earth of the first living object(s). We propose that hypothetical "ante-cells" reached a "dynamic although inorganic" state on the nascent Earth, and then, that these ante-cells gradually transformed into real cells once the Earth had cooled sufficiently for organic molecules to appear there. The vestigial pentameric RNAs would mark this key moment when the ante-cells have begun to join the organic world. (10.37871/jbres1912)
  DOI : 10.37871/jbres1912
• Proton acceleration from optically tailored high-density gas jet targets
  
  • Maitrallain A.
  • Marquès J.-R.
  • Bontemps K.
  • Bonvalet Julien
  • Atukpor Friday Emmanuel
  • Bagnoud V.
  • Carrière T.
  • Hannachi F.
  • Henares J.L.
  • Hornung J.
  • Huber A.
  • d'Humières E.
  • Lancia L.
  • Loiseau P.
  • Nicolaï P.
  • Santos J.
  • Tikhonchuk Vladimir T
  • Zielbauer B.
  • Tarisien M.
  Journal of Plasma Physics, Cambridge University Press (CUP), 2024, 90 (2), pp.965900201. Laser-driven ion acceleration is well established using solid targets mainly in the target normal sheath acceleration regime. To follow the increasing repetition rate available on high-intensity lasers, the use of high-density gas targets has been explored in the past decade. When interacting with targets reaching densities close to the critical one, the laser pulse can trigger different acceleration mechanisms such as Collisionless Shock Acceleration (CSA) or hole boring. Particle-in-cell simulations using ideal target profiles show that CSA can accelerate a collimated, narrow energy spread and few hundreds of megaelectronvolts ion beam on the laser axis. Nevertheless, in real experiments, the laser will not only interact with an overcritical, thin plasma slab with sharp density gradients, but also with lower density regions surrounding the core of the gas jet, extending to several hundreds of micrometres. The interaction of the laser with these lower density wings will lead to nonlinear effects that will reduce the available energy to drive the shock in the high-density region of the target. Optically tailoring this target could mitigate that issue. Recent experiments conducted on different laser facilities aimed at testing several tailoring configurations. We first tested a scheme with a copropagating picosecond prepulse to create a lower density plasma channel to facilitate the propagation of the main pulse, while the second one was a transverse tailoring driven by nanosecond laser pulses to generate blast waves and form a high-density plasma slab. The main results will be presented here and the methods compared. (10.1017/S0022377824000461)
  DOI : 10.1017/S0022377824000461