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)].

Radiochromic films (RCF) are commonly used in dosimetry for a wide range of radiation sources (electrons, protons, and photons) for medical, industrial, and scientific applications. They are multi-layered, which includes plastic substrate layers and sensitive layers that incorporate a radiation-sensitive dye. Quantitative dose can be retrieved by digitizing the film, provided that a prior calibration exists. Here, to calibrate the newly developed EBT3 and HDv2 RCFs from Gafchromic™, we used the Stanford Medical LINAC to deposit in the films various doses of 10 MeV photons, and by scanning the films using three independent EPSON Precision 2450 scanners, three independent EPSON V750 scanners, and two independent EPSON 11000XL scanners. The films were scanned in separate RGB channels, as well as in black and white, and film orientation was varied. We found that the green channel of the RGB scan and the grayscale channel are in fact quite consistent over the different models of the scanner, although this comes at the cost of a reduction in sensitivity (by a factor ∼2.5 compared to the red channel). To allow any user to extend the absolute calibration reported here to any other scanner, we furthermore provide a calibration curve of the EPSON 2450 scanner based on absolutely calibrated, commercially available, optical density filters.

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.

The dynamics of self-generated magnetic B-fields produced following the interaction of a high contrast, high intensity (I > 10¹⁹W cm⁻²) laser beam with thin (3 μm thick) solid (Al or Au) targets is investigated experimentally and numerically. Two main sources drive the growth of B-fields on the target surfaces. B-fields are first driven by laser-generated hot electron currents that relax over ∼10–20 ps. Over longer timescales, the hydrodynamic expansion of the bulk of the target into vacuum also generates B-field induced by non-collinear gradients of density and temperature. The laser irradiation of the target front side strongly localizes the energy deposition at the target front, in contrast to the target rear side, which is heated by fast electrons over a much larger area. This induces an asymmetry in the hydrodynamic expansion between the front and rear target surfaces, and consequently the associated B-fields are found strongly asymmetric. The sole long-lasting (>30 ps) B-fields are the ones growing on the target front surface, where they remain of extremely high strength (∼8–10 MG). These B-fields have been recently put by us in practical use for focusing laser-accelerated protons [B. Albertazzi et al., Rev. Sci. Instrum. 86, 043502 (2015)]; here we analyze in detail their dynamics and structure.

Magnetic reconnection can occur when two plasmas, having anti-parallel components of the magnetic field, encounter each other. In the reconnection plane, the anti-parallel component of the field is annihilated and its energy released in the plasma. Here, we investigate through laboratory experiments the reconnection between two flux tubes that are not strictly anti-parallel. Compression of the anti-parallel component of the magnetic field is observed, as well as a decrease of the reconnection efficiency. Concomitantly, we observe delayed plasma heating and enhanced particle acceleration. Three-dimensional hybrid simulations support these observations and highlight the plasma heating inhibition and reconnection efficiency reduction for these obliquely oriented flux tubes.