This PDF file contains the front matter associated with SPIE Proceedings Volume 12580, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

We study beam loading of electrons accelerated via the process of direct laser acceleration under the conditions of preformed plasma channels irradiated by ultra-intense laser pulses using analytical methods and particle-incell simulations in quasi-cylindrical geometry. We find the rates at which the electrons populate the beam for multi-petawatt peak power laser drivers. We show that the majority of accelerated electrons originate at the interface between the channel interior and channel wall and outline the underlying physical mechanism.

Plasma acceleration has been lately considered to become an auspicious technology for building a future multi-TeV electron-positron collider, leading to higher compactness of the device. Self-generated fields from laser-plasma interaction are, however, in contrast to electrons, usually not well-suited for positron focusing and on-axis guiding. In addition, an external positron source is required. Here, we study the method of direct laser acceleration of positrons. The positron generation is assured by an orthogonal collision of a multi-PW laser pulse and a GeV electron beam by the nonlinear Breit-Wheeler process. The acceleration subsequently takes place in a preformed plasma channel with a finite (tens-of-microns-long) radius. In this work, we examine how the choice of channel radius influences the process of acceleration. We show that this scheme is robust regarding the radius size. A significant number of the positrons is kept near the propagation axis, even if the channel radius was increased by almost 100 µm. The mechanism was examined by quasi-3D particle-in-cell simulation carried out with the OSIRIS framework.

Extreme Light Infrastructure–Nuclear Physics (ELI–NP) is a research infrastructure where the laser physics and nuclear physics scientific communities have joined their efforts to extend the research in the field of nuclear photonics to the interaction of extreme photon beams with matter. The infrastructure will provide high-power laser and gamma beams with unprecedented characteristics to be used for nuclear physics, plasma physics, quantum electrodynamics, material science research. The high–power laser system consisting of 2 x 10 PW lasers will provide pulses with intensities as high as 10²³ W/cm². First experiments with the high-power lasers at ELI–NP aim at measuring the magnitude and scaling of the achievable laser intensity via laser-gamma conversion efficiency and at studying new ion acceleration schemes to better understand and control high intensity laser–driven ion sources. A broad range of applications research program anchored in the unique capabilities of ELI–NP is currently being developed and addresses topics, such as: production of hadron therapy relevant particle beams, medical imaging research with laser x–ray sources, generation of radioisotopes of medical interest, materials in high radiation fields, industrial imaging. Currently ELI-NP is in a transition phase from implementation to operation. Following the successful commissioning of the high-power laser system and of the laser beam transport system, the commissioning of the experimental setups is now underway. The experimental setups will gradually be made available to users until the end of 2023.

The effect of picosecond ramp of ultrashort laser pulse is investigated with the help of particle-in-cell simulations. It is shown that the ramp changes cutoff energies and numbers of ions accelerated from laser-irradiated target depending on laser pulse intensity. It can also substantially change the interaction of the main high-intensity part of the pulse with thin membrane used as a plasma shutter to shape laser pulse temporal profile.

The interaction of high-intensity PW-class laser pulses with ultra-thin (tens of nm) foils provides interesting research conditions of high radiation pressure, strong self-generated magnetic fields and laser diffraction on generated aperture. When the laser pulse is transmitted through such a medium, its intensity profile can be enhanced, including generation of a steep-rising front, local intensity increase and improvement of its contrast. The use of a circularly polarized laser pulse is especially interesting in this setup, as the transmitted laser pulse can obtain a spiral-like intensity space profile. The structure is also transferred into the electron density profile of the expanded thin foil. In this work we compared the cases of linearly and circularly polarized laser pulse with the help of 3D particlein-cell simulations in interaction of an ultra-thin foil (plasma shutter) and the subsequent ion acceleration from the following target. The addition of the plasma shutter resulted in a generation of a spiral-like pulse in the case of circular polarization, significant reduction of the divergence of generated ion beam in the case of linear polarization and increase of maximal ion energy in both cases.

We study the interaction of two counter–propagating electromagnetic waves in vacuum in the Born–Infeld electrodynamics. First we investigate the Born case for linearly polarized beams, E · B = 0, i. e. G² = 0 (crossed field configuration), which is identical for Born–Infeld and Born electrodynamics; subsequently we study the general Born–Infeld case for beams which are nonlinearly polarized, G² ≠ 0. In both cases, we show that the nonlinear field equations decouple using self-similar solutions and investigate the shock wave formation. We show that the only nonlinear solutions are exceptional travelling wave solutions which propagate with constant speed and which do not turn into shocks. In the Born case, we naturally obtain exceptional wave solutions for counter–propagating (real photon– photon scattering) and for a co–propagating (non-interacting) beam orientation we investigate their direction of propagation. In the Born–Infeld case, we have additionally chosen the solutions which have constant phase velocities to match the limits of phase velocities of the background field in the Born case. We obtain two types of exceptional wave solutions, then we numerically analyze which phase velocities correspond to the counter– or co–propagating beams and subsequently we determine the direction of propagation of the exceptional waves.

Radiation reaction can severely affect the motion of ultra-relativistic particles in intense electromagnetic fields. Here, we study particle-in-cell (PIC) methods of kinetic modeling of radiation reaction in classical and quantum regimes. We test the methods of photon emission from highly energetic particles moving in strong electromagnetic field in two open-source PIC codes Smilei and EPOCH. We benchmark the codes and discuss the differences.