The talk starts with an introduction into the strong-field QED applicable for the collision of a high-energy electron beam with an ultra-strong laser pulse. For this purpose, relevant influences like radiative reaction, spin dynamics and pair production are discussed. The current state of experiments both implemented and under construction are presented. Emphasis on recent progress will be given on the generation and polarization of high-energy electron, positron and gamma-ray beams, plasma diagnostics, and tests of fundamental physics.

All-optical nonlinear Breit-Wheeler pair production with gamma-flash photons High-power laser facilities give experimental access to fundamental strong-field quantum electrodynamics processes. A key effect to be explored is the nonlinear Breit-Wheeler process: the conversion of high-energy photons into electron-positron pairs through the interaction with a strong electromagnetic field. A major challenge to observing nonlinear Breit-Wheeler pair production experimentally is first having a suitable source of high-energy photons. We outline a simple all-optical setup which efficiently generates photons through the so-called gamma-flash mechanism by irradiating a solid target with a high-power laser. We consider the collision of these photons with a secondary laser, and systematically discuss the prospects for exploring the nonlinear Breit-Wheeler process at current and next-generation high-power laser facilities.

In the presence of an electromagnetic background plane-wave field, electron, positron, and photon states are not stable, because electrons and positrons emit photons and photons decay into electronpositron pairs. This decay of the particle states leads to an exponential damping term in the probabilities of single nonlinear Compton scattering and nonlinear Breit-Wheeler pair production. We present analytical and numerical investigations for the probabilities of nonlinear Compton scattering and nonlinear Breit-Wheeler pair production including the particle states decay.

Electron-laser colliders are a unique tool to investigate different fundamental phenomena, as for example the Breit-Wheeler process. Several experiments are working in this direction as of now, both based on conventional electron accelerator technology or on all-optical schemes. In the landscape of high power laser facilities, ELI-Beamlines has two unique lasers which have the potential to enable laser-electron collisions at unprecedented parameters: L3-HAPLS (30 J, 30 fs, 10 Hz) and L4-Aton (1.5 kJ, 150 fs, 100s shots/day). In ELI-ELBA, the L3 laser pulses are split in two by a 50:50 wavefront splitting mirror. The central part of the beam is focused by a 10 meter focal length off-axis parabola into a gas jet to generate GeV electron beams by laser wakefield acceleration. The outer part of the beam is focused on the electron beam by a f/1.5 off-axis parabola with a hole. The installation of ELI-ELBA and the results of the technical commissioning at low-power (L3 front-end) will be presented, along with the experiments proposed by the user community. The designed upgrade of ELI-ELBA for 10 PW experiments will be also presented.

The relativistic flying mirror is a high-density electron layer which is frequently observed in the relativistic plasma produced by high-power laser pulses. The focused field strength reflected by the relativistic flying mirror can be intensified beyond the conventional limit defined by the diffraction. The relativistic flying mirror is conceived as a promising candidate for studying the strong-field quantum electrodynamic effect, by boosting the focused laser intensity toward the Schwinger field limit. In this presentation, we discuss the optical characteristics of the relativistic flying mirror and its applicability to the strong-field quantum electrodynamics study.

The PW-class lasers can generate electromagnetic fields of such magnitude that the radiation emission starts to dominate the particle motion. At this point the effects of quantum electrodynamics (QED) in strong fields become crucial. Recent progress in laser technology, high-power lasers provide a platform to create and probe such fields in the laboratory.

The emergence of petawatt lasers focused on relativistic intensities enables all-optical laboratory generation of intense magnetic fields in plasmas, which are of great interest due to their ubiquity in astrophysical phenomena. We report our study of the generation of spatially extended and long-lived intense magnetic fields. We show that such magnetic fields, scaling up to the gigagauss range, can be generated by the interaction of petawatt laser pulses with relativistically underdense plasma. With three-dimensional particle-in-cell simulations, we investigate the generation of magnetic fields with strengths up to 10^10 G and perform a large multi-parametric study of the magnetic field in dependence on dimensionless laser amplitude a0 and normalized plasma density ne/nc. The numerical results yield scaling laws that closely follow derived analytical result B ≈ (a0ne/nc)^1/2, and further show a close match with previous experimental works. Furthermore, we show in three-dimensional geometry that the decay of the magnetic wake is governed by current filament bending instability, which develops similarly to von Kármán vortex street in its nonlinear stage. We envision interactions of relativistic electrons with studied intense magnetic wakes for probing of strong field quantum electrodynamics in magnetized plasmas. Our results pave the way towards the generation of intense, tunable, and long-lived magnetic fields in plasmas at various laboratory conditions, which lead to innumerable applications in plasma physics, fundamental physics, and laboratory astrophysics.

A theoretical study is made of the main regimes of interaction of relativistically strong electromagnetic waves with near critical density plasma under conditions in which the radiation from particles plays a dominant role. The discussion is focused on the electromagnetic wave dynamics in the case of the transverse and longitudinal mode nonlinear coupling. The radiation friction effects implemented into the theoretical model result in extremely fast, on the scale of few oscillation periods, decay of the wave with substantially high intensity. The consequences of the electromagnetic wave decay for the gamma-ray flash generation in laser-matter interaction are also discussed.

At CoReLS a 20 fs, 4 PW Ti:Sapphire laser, constructed in 2017, has been applied for producing multi-GeV electron beams using the laser wakefield acceleration scheme. For the investigation of physical processes in strong-field QED, we explored nonlinear Compton scattering between a multi-GeV electron beam and an ultrahigh intensity laser in an all-optical setup. The gamma-ray signals from the NCS were measured with LYSO scintillation detectors. We could confirm the nonlinear Compton scattering between a GeV electron and several hundred laser photons by obtaining the gamma-ray signal far exceeding the cutoff energy of linear Compton scattering.

We report on the High-Power Laser System (HPLS) performance of the Extreme Light Infrastructure - Nuclear Physics (ELI-NP) during the commissioning and the beam delivery. The HPLS uses a hybrid CPA – OPCPA (Optical Parametric CPA) architecture and has two arms enabling it to deliver 2 beams with 10 PW laser pulses at a repetition rate of 1 shot per minute. In addition, it provides two outputs at 100TW and two outputs at 1PW peak power levels. A detailed description of the HPLS is presented in the reference [1, 2]. Funding. Extreme Light Infrastructure Nuclear Physics (ELI-NP) Phase II, is a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund and the Competitiveness Operational Programme (1/07.07.2016, COP, ID 1334). This work was supported by the contract sponsored by the Ministry of Research and Innovation Nulceu Program. Acknowledgements. We gratefully acknowledge the contribution of the entire Thales, Alsyom/Seiv and ELI-NP teams and collaborators. References [1] F. Lureau, et al., High Power Laser Sci. Eng., 8, E43 (2020) [2] C. Radier, High Power Laser Sci. Eng., 10, E21. (2022)

Several laser facilities reaching unprecedented peak powers in the multi-petawatt regime are currently being commissioned worldwide, opening up new and exciting avenues for fundamental and applied research. In this talk, an overview of current and planned work in this area will be given, focusing on the opportunities that these facilities will offer for revolutionary work not only in fundamental science but also in their exploitation in healthcare, industry, and homeland security

Electron-positron pairs can be generated with lasers in various configurations, using either Breit-Wheeler or Bethe-Heitler pair production. In some cases, the very same laser can provide direct laser acceleration (DLA) of leptons in the radiation reaction dominated regime. The DLA scheme has already provided electron beams of ~nC charge in experiments. Here we show what can be accomplished with near-future laser facilities with a special consideration of L4 beamline at ELI beamlines. Increasing the laser power is bound to augment the DLA electron charge content even further. The field structure formed due to electron beam loading allows for accelerating positrons without defocusing them. What is more, the interaction in the radiation dominated regime will provide a high flux of emitted photons, in hard x-ray and gamma-ray range. These photons can then be used as a seed for electron-positron pair creation, as well as a radiation source for applications. This work was supported by FCT grants CEECIND/01906/2018, PTDC/FISPLA/3800/2021. We acknowledge PRACE for granting access to MareNostrum in BSC, Spain.

Light, sufficiently intense and brief, can turn passive matter into dynamical objects unlocking the doors to the tremendous potential of nonlinear science. This type of exotic interaction holds key to solutions of many problems in fundamental and applied science. Such interactions can be accessed at high intensities with laser parameters suitably tuned to the domain of interest. The diverse lasers and experimental platforms at ELI-ALPS strives to achieve this goal. In this presentation I would describe the accessible domains, several scientific achievements and advancements in the recent past and the future scientific and technological potential of ELI-ALPS.

This conference presentation was prepared for SPIE Optics + Optoelectronics, 2023.

This conference presentation was prepared for SPIE Optics + Optoelectronics, 2023.

The ELI Beamlines Facility is a pillar of the ELI (Extreme Light Infrastructure) pan-European Research Infrastructure hosting the world’s most intense laser sources. ELI Beamlines developed and operates four cutting edge high-peak, high-average power femtosecond laser systems and offers a unique combination of primary (lasers) and secondary (high-energy particles and X-rays) sources to the international user community. Currently, several beamlines are operational and being upgraded to reach their full performances, while other beamlines are in their commissioning phase. An overview of the current user offer in terms of primary/secondary sources and user stations will be presented.

Laser pulses with peak power of beyond 1 PW have become increasingly available. The associated strong electromagnetic fields unfolding in the focus can drive prompt, microscopic particle acceleration in plasmas. The emitted bunches stand out in comparison to radio frequency sources and enable novel experimental approaches to the interaction of energetic, ionising radiation with matter. Even manipulation of quantum vacuum properties seems accessible. Addressing a general audience, my presentation will convey the core principles of the physics and applications and address prominent challenges that require urgent solutions.

This conference presentation was prepared for SPIE Optics + Optoelectronics, 2023.

The experimental campaign for the commissioning of the 1 PW laser system has been accomplished in 2022, and the campaign for the 10 PW commissioning has started in October 2022. The goal of the experimental campaigns is to assess the performance of the High-Power Laser System (HPLS) and the target areas by investigating the laser-matter interaction mainly via acceleration of particles. A large amount of data has been acquired during the 1 PW campaign both on ion and electron acceleration, while the 10 PW campaign is soon expected to acquire data on ion acceleration from the experiment undertaken at the beginning of this year. The HPLS is a Ti:Sa based laser with central wavelength around 810 nm, it can deliver a 1 PW laser beam with a maximum energy of 24 J and a pulse duration of about 24 fs and a repetition rate of 1 Hz; while the 10 PW laser beam can deliver 240 J in 23 fs with a repetition rate of 1 shot per minute. The HPLS has shown good stability and reproducibility of the main parameters during the full power shots, and a good focusability. In this talk, the extensive results obtained with the 1 PW system and conceivably the ones that will be soon obtained with the 10 PW will be presented. Acknowledgements. I gratefully acknowledge the contribution of Thales, and ELI-NP teams and collaborators.