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.

The generation of non-destructive pulsed magnetic fields of 100 T involves high mechanical stress, due to the Lorentz forces, sustainable by few conductors. At LNCMI, in the inner coil (the most mechanically stressed) of the 100 T triple coil system a Cu-Nb commercial conductor is used. This work explains firstly how a new bi-material design of the inner coil allows to reduce the quantity of the Cu-Nb wire used. Secondly, in order to replace this commercial Cu-Nb wire, the way to increase the volume of Ag-Cu composite conductors produced at CIRIMAT and LNCMI by powder metallurgy, Spark Plasma Sintering and wire drawing at room temperature is discussed.

The propagation and energy coupling of intense laser beams in plasmas are critical issues in inertial confinement fusion. Applying magnetic fields to such a setup has been shown to enhance fuel confinement and heating. Here we report on experimental measurements demonstrating improved transmission and increased smoothing of a high-power laser beam propagating in a magnetized underdense plasma. We also measure enhanced backscattering, which our kinetic simulations show is due to magnetic confinement of hot electrons, thus leading to reduced target preheating.

Colliding collisionless shocks appear in a great variety of astrophysical phenomena and are thought to be possible sources of particle acceleration in the Universe. We have previously investigated particle acceleration induced by single super-critical shocks (whose magnetosonic Mach number is higher than the critical value of 2.7) (Yao et al. , Nat. Phys. , vol. 17, issue 10, 2021, pp. 1177–1182; Yao et al. , Matter Radiat. Extrem. , vol. 7, issue 1, 2022, 014402), as well as the collision of two sub-critical shocks (Fazzini et al. , Astron. Astrophys. , vol. 665, 2022, A87). Here, we propose to make measurements of accelerated particles from interpenetrating super-critical shocks to observe the ‘phase-locking effect’ (Fazzini et al. , Astron. Astrophys. , vol. 665, 2022, A87) from such an event. This effect is predicted to significantly boost the energy spectrum of the energized ions compared with a single super-critical collisionless shock. We thus anticipate that the results obtained in the proposed experiment could have a significant impact on our understanding of one type of primary source (acceleration of thermal ions as opposed to secondary acceleration mechanisms of already energetic ions) of ion energization of particles in the Universe.

We describe a setup able to generate a rotating or alternating low-frequency (up to 10 Hz) magnetic field (up to 120 mT) for biological applications inside a 6 cm in diameter and 5 cm in height cylindrical space. It is suitable to insert several Petri dishes for cell death experiments and mice for in vivo ones. Since a particular attention was given to the field homogeneity, it is based on a six-pole electromagnet. The characteristics of the field are changed by varying the phase, amplitude or frequency of the electrical currents going through the coils, using a micro-controller-based human-machine interface and a RL chopper, which is described. The results of the magnetic simulations run to optimize the global design are provided. The cooling of the electromagnet is done using a chiller, and the sample temperature regulation using an air blower. All details on the mechanical, electrical and electronic elements, on the mounting, and on the programing are provided, so the setup can be reproduced. Suggestions for a further improvement of the electrical efficiency are given. This setup has already been used to demonstrate the possibility to kill cells using targeted magnetic nanoparticles and low-frequency magnetic fields.

Collisionless shocks are ubiquitous in the Universe and are held responsible for the production of nonthermal particles and high-energy radiation. In the absence of particle collisions in the system, theory shows that the interaction of an expanding plasma with a pre-existing electromagnetic structure (as in our case) is able to induce energy dissipation and allow shock formation. Shock formation can alternatively take place when two plasmas interact, through microscopic instabilities inducing electromagnetic fields that are able in turn to mediate energy dissipation and shock formation. Using our platform in which we couple a rapidly expanding plasma induced by high-power lasers (JLF/Titan at LLNL and LULI2000) with high-strength magnetic fields, we have investigated the generation of a magnetized collisionless shock and the associated particle energization. We have characterized the shock as being collisionless and supercritical. We report here on measurements of the plasma density and temperature, the electromagnetic field structures, and the particle energization in the experiments, under various conditions of ambient plasma and magnetic field. We have also modeled the formation of the shocks using macroscopic hydrodynamic simulations and the associated particle acceleration using kinetic particle-in-cell simulations. As a companion paper to Yao et al. [Nat. Phys. 17, 1177–1182 (2021)], here we show additional results of the experiments and simulations, providing more information to allow their reproduction and to demonstrate the robustness of our interpretation of the proton energization mechanism as being shock surfing acceleration.

The Laboratoire National des Champs Magnétiques Intenses (LNCMI) is a French host facility for experiments in high magnetic fields. Internal research is carried out in the lab and experimental time is allocated to external researchers. The LNCMI is a founding member of the European Magnetic Field Laboratory (EMFL) with the Hochfeld-Magnetlabor in Dresden (HLD) and the High Field Magnet Laboratory in Nijmegen (HFML). While static fields up to 37 T are produced in Grenoble, the Toulouse facility is dedicated to the generation of pulsed magnetic fields. It offers 98.8 T nondestructively and 209 T with a semi-destructive Megagauss installation. We focus here on the nondestructive activities. All the electromagnets that generate these high fields and their associated capacitor banks are developed in the laboratory. Here, we present the developments realized during the last five years with the complete reconstruction of the main capacitor banks of the laboratory.

Magnetized laser-produced plasmas are central to many studies in laboratory astrophysics, in inertial confinement fusion, and in industrial applications. Here, we present the results of large-scale three-dimensional magnetohydrodynamic simulations of the dynamics of a laser-produced plasma expanding into a transverse magnetic field with a strength of tens of teslas. The simulations show the plasma being confined by the strong magnetic field into a slender slab structured by the magnetized Rayleigh–Taylor instability that develops at the plasma–vacuum interface. We find that when the initial velocity of the plume is perturbed, the slab can develop kink-like motions that disrupt its propagation.

Colliding collisionless shocks appear in a great variety of astrophysical phenomena and are thought to be possible sources of particle acceleration in the Universe. To investigate the detailed dynamics of this phenomenon, we have performed a dedicated laboratory experiment. We have generated two counter-streaming subcritical collisionless magnetized shocks by irradiating two teflon (CF$_2$) targets with 100 J, 1 ns laser beams on the LULI2000 laser facility. The interaction region between the plasma flows was pre-filled with a low density background hydrogen plasma and initialized with an externally applied homogeneous magnetic field perpendicular to the shocks. We report here on measurements of the plasma density and temperature during the formation of the supercritical shocks, their transition to subcritical, and final interpenetration. We have also modeled the macroscopic evolution of the system via hydrodynamic simulations and the microphysics at play during the interaction via Particle-In-Cell simulations. The main goal was to understand what was the effect of the second shock on particle energization. We found that in the presence of two shocks the ambient ions reach energies around 1.5 times of the ones obtained with single shocks. Both the presence of the downstream zone of the second shock and of the downstream zone common for the two shocks play a role in the different energization: the characteristics of the perpendicular electric fields in the two areas allow, indeed, certain particles to keep being accelerated or to avoid being decelerated.

The present work is aimed at the experimental study of the dynamics of laser-induced plasma immersed in a strong poloidal magnetic field with a variable orientation ( $0^{\circ}-90^{\circ}$ depending on the plasma expansion) and amplitude (up to 30 T). The significance of such studies is especially important for the tasks of laboratory astrophysics and inertial confinement fusion. Electron density and temperature profiles are measured, effects related with plasma collimation, accumulation, as well as separation, generation of instabilities and shocks by the magnetic field are discussed.

Abstract We analyze, using experiments and 3D MHD numerical simulations, the dynamic and radiative properties of a plasma ablated by a laser (1 ns, 10 $$^{12}$$ 12 –10 $$^{13}$$ 13 W/cm $$^2$$ 2 ) from a solid target as it expands into a homogeneous, strong magnetic field (up to 30 T) that is transverse to its main expansion axis. We find that as early as 2 ns after the start of the expansion, the plasma becomes constrained by the magnetic field. As the magnetic field strength is increased, more plasma is confined close to the target and is heated by magnetic compression. We also observe that after $$\sim 8$$ ∼ 8 ns, the plasma is being overall shaped in a slab, with the plasma being compressed perpendicularly to the magnetic field, and being extended along the magnetic field direction. This dense slab rapidly expands into vacuum; however, it contains only $$\sim 2\%$$ ∼ 2 % of the total plasma. As a result of the higher density and increased heating of the plasma confined against the laser-irradiated solid target, there is a net enhancement of the total X-ray emissivity induced by the magnetization.

Aims. EXor-type objects are protostars that display powerful UV-optical outbursts caused by intermittent and powerful events of magnetospheric accretion. These objects are not yet well investigated and are quite difficult to characterize. Several parameters, such as plasma stream velocities, characteristic densities, and temperatures, can be retrieved from present observations. As of yet, however, there is no information about the magnetic field values and the exact underlying accretion scenario is also under discussion. Methods. We use laboratory plasmas, created by a high power laser impacting a solid target or by a plasma gun injector, and make these plasmas propagate perpendicularly to a strong external magnetic field. The propagating plasmas are found to be well scaled to the presently inferred parameters of EXor-type accretion event, thus allowing us to study the behaviour of such episodic accretion processes in scaled conditions. Results. We propose a scenario of additional matter accretion in the equatorial plane, which claims to explain the increased accretion rates of the EXor objects, supported by the experimental demonstration of effective plasma propagation across the magnetic field. In particular, our laboratory investigation allows us to determine that the field strength in the accretion stream of EXor objects, in a position intermediate between the truncation radius and the stellar surface, should be of the order of 100 G. This, in turn, suggests a field strength of a few kilogausses on the stellar surface, which is similar to values inferred from observations of classical T Tauri stars.

The shaping of astrophysical outflows into bright, dense, and collimated jets due to magnetic pressure is here investigated using laboratory experiments. Here we look at the impact on jet collimation of a misalignment between the outflow, as it stems from the source, and the magnetic field. For small misalignments, a magnetic nozzle forms and redirects the outflow in a collimated jet. For growing misalignments, this nozzle becomes increasingly asymmetric, disrupting jet formation. Our results thus suggest outflow/magnetic field misalignment to be a plausible key process regulating jet collimation in a variety of objects from our Sun’s outflows to extragalatic jets. Furthermore, they provide a possible interpretation for the observed structuring of astrophysical jets. Jet modulation could be interpreted as the signature of changes over time in the outflow/ambient field angle, and the change in the direction of the jet could be the signature of changes in the direction of the ambient field.

In this paper, we describe a novel pulsed magnet, called foil coil, which can deliver a field transverse to the light propagation of more than 10 T over about 0.8 m operating without cryogenic equipment. It has been designed for linear magnetic birefringence measurements. We report on testing the coil and also show some physics data taken in vacuum during its commissioning in the framework of the Biréfringence Magnétique du Vide (BMV) apparatus, with special attention to noise induced by the pulse itself. Finally, we compare the preliminary results obtained here with data from the previous BMV coil.

Charged particles can be accelerated to high energies by collisionless shock waves in astrophysical environments, such as supernova remnants. By interacting with the magnetized ambient medium, these shocks can transfer energy to particles. Despite increasing efforts in the characterization of these shocks from satellite measurements at the Earth's bow shock and powerful numerical simulations, the underlying acceleration mechanism or a combination thereof is still widely debated. Here, we show that astrophysically relevant super-critical quasi-perpendicular magnetized collisionless shocks can be produced and characterized in the laboratory. We observe characteristics of super-criticality in the shock profile as well as the energization of protons picked up from the ambient gas to hundreds of keV. Kinetic simulations modelling the laboratory experiment identified shock surfing as the proton acceleration mechanism. Our observations not only provide the direct evidence of early stage ion energization by collisionless shocks, but they also highlight the role this particular mechanism plays in energizing ambient ions to feed further stages of acceleration. Furthermore, our results open the door to future laboratory experiments investigating the possible transition to other mechanisms, when increasing the magnetic field strength, or the effect induced shock front ripples could have on acceleration processes.

Aims. Investigating the process of matter accretion onto forming stars through scaled experiments in the laboratory is important in order to better understand star and planetary system formation and evolution. Such experiments can indeed complement observations by providing access to the processes with spatial and temporal resolution. A previous investigation revealed the existence of a two-component stream: a hot shell surrounding a cooler inner stream. The shell was formed by matter laterally ejected upon impact and refocused by the local magnetic field. That laboratory investigation was limited to normal incidence impacts. However, in young stellar objects, the complex structure of magnetic fields causes variability of the incident angles of the accretion columns. This led us to undertake an investigation, using laboratory plasmas, of the consequence of having a slanted accretion impacting a young star. Methods. Here, we used high power laser interactions and strong magnetic field generation in the laboratory, complemented by numerical simulations, to study the asymmetry induced upon accretion structures when columns of matter impact the surface of young stars with an oblique angle. Results. Compared to the scenario where matter accretes perpendicularly to the star surface, we observe a strongly asymmetric plasma structure, strong lateral ejecta of matter, poor confinement of the accreted material, and reduced heating compared to the normal incidence case. Thus, slanted accretion is a configuration that seems to be capable of inducing perturbations of the chromosphere and hence possibly influencing the level of activity of the corona.

In many natural phenomena in space (cosmic-rays, fast winds), non-thermal ion populations are produced, with wave-particle interactions in self-induced electromagnetic turbulence being suspected to be mediators. However, the processes by which the electromagnetic energy is bestowed upon the particles is debated, and in some cases requires field compression. Here we show that laboratory experiments using high-power lasers and external strong magnetic field can be used to infer magnetic field compression in the interpenetration of two collisionless, high-velocity (0.01–0.1c) quasi-neutral plasma flows. This is evidenced through observed plasma stagnation at the flows collision point, which Particle-in-Cell (PIC) simulations suggest to be the signature of magnetic field compression into a thin layer, followed by its dislocation into magnetic vortices. Acceleration of protons from the plasma collision is observed as well. As a possible scenario, with 1D and 2D PIC simulations we consider a compression of the vortices against dense plasma remnants.

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Laser irradiation of solid targets can drive short and high-charge relativistic electron bunches over micron-scale acceleration gradients. However, for a long time, this technique was not considered a viable means of electron acceleration due to the large intrinsic divergence (∼50° half-angle) of the electrons. Recently, a reduction in this divergence to 10°–20° half-angle has been obtained, using plasma-based magnetic fields or very high contrast laser pulses to extract the electrons into the vacuum. Here we show that we can further improve the electron beam collimation, down to ∼1.5° half-angle, of a high-charge (6 nC) beam, and in a highly reproducible manner, while using standard stand-alone 100 TW-class laser pulses. This is obtained by embedding the laser-target interaction in an external, large-scale (cm), homogeneous, extremely stable, and high-strength (20 T) magnetic field that is independent of the laser. With upcoming multi-PW, high repetition-rate lasers, this technique opens the door to achieving even higher charges (>100 nC).