This paper presents a four-channel prototype system for the geometric combining and coherent addition of tightly focused femtosecond laser radiation into a standing-wave field configuration. A stabilization system for beam pointing and relative phase of the four optical channels has been implemented, and its performance has been experimentally demonstrated. To characterize the standing-wave electromagnetic field distribution at the main focus of the system, an original measurement technique based on a fiber subwavelength optical probe has been employed. This work has been conducted in support of the exawatt-scale XCELS project.

When two identical counter-propagating laser pulses sharply focused by parabolic mirrors overlap, the electric field amplitude is optimized based on vector calculations. An optimal aspect ratio of a rectangular laser beam and f-number of a parabolic mirror that maximizes the field during focusing, as well as an optimal frequency spectrum of the pulse at the compressor output within a specified spectral range, is determined. The potential for further increasing the field in focus by optimizing the spatial intensity distribution in the near field is explored. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

The paper describes the design of a microscope for studying a betatron radiation source based on the PEARL femtosecond laser complex in the SXR and EUV wavelength range. The main optical element of the microscope is a spherical Schwarzschild objective a x5 magnification. The device allows to study the size and spatial structure of the interaction area of laser radiation with matter, at a selected wavelength in the EUV or SXR range with a resolution of delta x=2.75 μm. The operation wavelength (λ=13.5 nm) is set by multilayer X-ray mirrors. Thin-film absorption filters are used to suppress the background component of the signal. Keywords: SXR and EUV radiation, betatron radiation, imaging x-ray optics, SXR microscope.

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.

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. The interaction of magnetic fields embedded in plasmas is central to many astrophysical phenomena. Here, authors show that plasma flow disruption caused by enhanced magnetic field is unexpectedly small compared to magnetic field compression by shocks, which significantly limits the growth of field strength.

Weibel instability was observed experimentally in plasma generated after irradiation a solid target with a 250 TW ultrashort laser pulse at the PEARL petawatt laser facility. The influence of laser radiation intensity and an external magnetic field on generation of the Weibel instability has been investigated.

The PEARL laser -plasma complex is set up on the basis of a petawatt laser and allows a wide range of experiments in laser -plasma interactions, including particle acceleration, X-ray generation, and research in the area of high energy density physics. Constant work to improve the system makes it possible not only to systematically expand experimental capabilities but also to develop new technologies for megascience class facilities. The paper outlines possible experimental scenarios for using the laser and provides a description of experiments already carried out with the laser in a broad range of areas.

We performed an experiment on the acceleration of electrons in the laser peeler regime during the interaction of a focused subpetawatt laser pulses with solid-state targets. Electrons with energies up to 70 MeV were produced, and their directional pattern was determined. The use of serrated targets led to an increase in the maximum energies and the number of accelerated electrons. A numerical study conducted using particle-in-cell simulation showed good agreement with the experimental results.

Context. Numerical studies as well as scaled laboratory experiments suggest that bipolar outflows arising from young stellar objects (YSOs) could be collimated into narrow and stable jets as a result of their interaction with a poloidal magnetic field. However, this magnetic collimation mechanism was demonstrated only for the simplified topology of the uniform poloidal magnetic field. Aims. We have extended the experimental studies to the case of a plasma outflow expanding in a region of strong poloidal magnetic field and then propagating through divergent magnetic field lines. In this case the magnetic field distribution is closer to the hourglass magnetic field distribution expected near YSOs. Our aim was to find out whether (and under what conditions) magnetic collimation is possible in such a strongly nonuniform B-field configuration. Methods. The experiments were carried out on the PEARL high-power laser facility. The laser produced plasma outflow was embedded in a strong (~10 T ) magnetic field generated by our unique magnetic system. The morphology and dynamics of the plasma were diagnosed with a Mach-Zehnder interferometer. Results. Laboratory experiments and 3D numerical modeling allow us to reveal the various stages of plasma jet formation in a divergent poloidal magnetic field. The results show (i) that there is a fundamental possibility for magnetic collimation of a plasma outflow in a divergent magnetic field; (ii) that there is good scalability of astrophysical and laboratory flows; (iii) that the conditions for the formation of a magnetic nozzle, hence collimation by poloidal magnetic field, have been met; and (iv) that the propagation of the jet proceeds unimpeded through the region of weak and strongly divergent magnetic fields, maintaining a high aspect ratio. Conclusions. Since we have verified that the laboratory plasma scales favorably to YSO jets and outflows, our laboratory modeling hints at the possibility of the YSO jet collimation in a divergent poloidal magnetic field.

Structural instabilities that develop during pulsed injection of dense plasma jets into vacuum in the presence of an external quasi-homogeneous magnetic field are studied by high-speed photography using ICCD cameras. The experiments are carried out in the chamber of the “Krot” stand, which has record-breaking dimensions in its class of installations (diameter—3 m, length of the working section—10 m), and makes it possible to study plasma dynamics by various diagnostic methods at scales of more than 1 m both along the magnetic field and in the direction transverse to the magnetic field. During injection along the magnetic field, a transverse collimation of the flow of ionized matter and the development of a flute instability of the plasma boundary are observed, which, at the late stages of expansion, leads to the plasma leaving the injection region in the form of several jets across the field. During transverse injection, the formation of a collimated flow, a “plasma sheet,” is observed, in which, as the plasma moves across the field, inhomogeneous structures develop in the direction of injection.

A method for measuring the intensity of focused high-power laser pulses based on numerical simulation of high-harmonic generation in the laser peeler regime is proposed.The dependence of the efficiency of high-harmonic generation on the laser pulse intensity and the spatial parameters during interaction with solid targets is studied numerically.The simulation clearly shows that the amplitude of the generated harmonics depends on the laser pulse parameters.The proposed method is simpler than similar intensity measurement techniques and does not require complex preparation.

We propose a scheme for efficient directional emission of laser-driven wakefields from a magnetized plasma. In the scheme, a laser–plasma interaction region is sandwiched between a pair of dielectric prisms of total internal reflection. The wakefields, propagating in the plasma at different angles to the laser beam, are cumulated by the prisms and radiated to free space in the direction of the laser beam. For magnetic fields <100 T, a 50-fs laser pulse with 1-J energy can generate long lasting (hundreds of ps) multicycle terahertz radiation with mJ-level energy. For a 500-T field, the laser pulse can generate terahertz bursts with a uniform spectrum in the ∼7–14 THz interval with ten-mJ-level energy.

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.

The eXawatt Center for Extreme Light Studies project aimed to create a large scientific infrastructure based on lasers with giant peak power. The project relies on the significant progress achieved in the last decade. The planned infrastructure will incorporate a unique light source with a pulse power of 600 PW using optical parametric chirped pulse amplification in large-aperture KD2PO4, deuterated potassium dihydrogen phosphate crystals. The interaction of such laser radiation with matter represents a completely new fundamental physics. The direct study of the space-time structure of vacuums and other unknown phenomena at the frontier of high-energy physics and the physics of superstrong fields will be challenged. Expected applications will include the development of compact particle accelerators, the generation of ultrashort pulses of hard X-ray and gamma radiation for material science enabling one to probe material samples with unprecedented spatial and temporal resolution, the development of new radiation and particle sources, etc. The paper is translation from Russian [Kvantovaya Elektronika 53, 95 (2023)].

We present the first experimental results obtained with a setup created on the basis of the PEARL laser facility for studying the processes of generating terahertz radiation from laser wake fields which are formed during the propagation of a high-power femtosecond laser pulse in a rarefied plasma. In particular, the occurrence of terahertz generation in the case where the laser–plasma interaction region is located between a pair of dielectric prisms of total internal reflection is demonstrated. The dependence of the terahertz radiation energy on the energy of a femtosecond laser pulse and on the plasma density is studied.

The enhancement of the resolution of pump-probe optical diagnostics for ultrafast processes by compressing the probe pulse duration using the CafCA approach [1] is considered on an example of the BISER soft-X-ray generation [2] with the J-KAREN-P laser [3].

Spatially nonuniform beam shape induces an inhomogeneous phase during nonlinear pulse compression. It makes the beam focusing on a target a challenging task. In this work possible strategies for wave-front correction are considered.

The use of the post-compression technique ensures gain in laser pulse peak power but at the same time degrades beam focusability due to the nonlinear wavefront distortions caused by a spatially nonuniform beam profile. In this paper a substantial focusability improvement of a post-compressed laser pulse by means of adaptive optics was demonstrated experimentally. The Strehl ratio increase from 0.16 to 0.43 was measured. Simulations showed that the peak intensity in this case reaches 0.52 of the theoretical limit.