As an alternative to Compton backscattering and bremsstrahlung, the process of colliding high-energy electron beams with strong laser fields can more efficiently provide both a cleaner and brighter source of photons in the multi-GeV range for fundamental studies in nuclear and quark-gluon physics. In order to favor the emission of high-energy quanta and minimize their decay into electron-positron pairs, the fields must not only be sufficiently strong, but also well localized. We here examine these aspects and develop the concept of a laser-particle collider tailored for high-energy photon generation. We show that the use of multiple colliding laser pulses with 0.4 PW of total power is capable of converting more than 18% of multi-GeV electrons passing through the high-field region into photons, each of which carries more than half of the electron initial energy.

The main direction proposed by the community of experts in the field of laser-driven ion acceleration is to improve particle beam features (maximum energy, charge, emittance, divergence, monochromaticity, shot-to-shot stability) in order to demonstrate reliable and compact approaches to be used for multidisciplinary applications, thus, in principle, reducing the overall cost of a laser-based facility compared to a conventional accelerator one and, at the same time, demonstrating innovative and more effective sample irradiation geometries. The mission of the laser-driven ion target area at ELI-Beamlines (Extreme Light Infrastructure) in Dolní Břežany, Czech Republic, called ELI Multidisciplinary Applications of laser-Ion Acceleration (ELIMAIA) , is to provide stable, fully characterized and tuneable beams of particles accelerated by Petawatt-class lasers and to offer them to the user community for multidisciplinary applications. The ELIMAIA beamline has been designed and developed at the Institute of Physics of the Academy of Science of the Czech Republic (IoP-ASCR) in Prague and at the National Laboratories of Southern Italy of the National Institute for Nuclear Physics (LNS-INFN) in Catania (Italy). An international scientific network particularly interested in future applications of laser driven ions for hadrontherapy, ELI MEDical applications (ELIMED), has been established around the implementation of the ELIMAIA experimental system. The basic technology used for ELIMAIA research and development, along with envisioned parameters of such user beamline will be described and discussed.

We discuss and numerically test a method for direct and unambiguous measurement of ultrahigh laser intensities exceeding ${10}^{20}\mathrm{W}/{\mathrm{cm}}^2$. The method is based on the use of multiple sequential tunneling ionization of heavy atoms with sufficiently high ionization potentials. We show that, due to a highly nonlinear dependence of tunneling ionization rates on the electromagnetic field strength, an offset in the charge distribution of ions appears sufficiently sensitive to the peak value of intensity in the laser focus. A simple analytic theory is presented which helps in estimating the maximal charge state produced at a given intensity via the tunnel-ionization mechanism. The theory also allows for calculating qualitatively a distribution in charge states generated in different parts of the laser focus. These qualitative predictions are supported by numerical simulations of the tunneling cascades developed in the interaction of a short intense laser pulse with a low-density target consisting of noble gases including argon, krypton, and xenon. Results of these simulations show that, using this technique, intensities in the range ${10}^{20}–{10}^{24}\mathrm{W}/{\mathrm{cm}}^2$ can be measured with sufficient reliability. The method could be extremely useful and of high demand in view of the expected commissioning of several new laser facilities capable of delivering ultrapowerful light pulses in this domain of intensities.

Using quantum electrodynamics particle-in-cell simulations, we optimize the gamma flare (γ-flare) generation scheme from the interaction of a high power petawatt-class laser pulse with a tailored cryogenic hydrogen target having an extended preplasma corona. We show that it is possible to generate an energetic flare of photons with energies in the GeV range and the total flare energy being on a kilojoule level with efficient conversion of the laser pulse energy to γ-photons. We discuss how the target engineering and the laser pulse parameters influence the γ-flare generation efficiency. This type of experimental setup for a laser-based γ-source would be feasible for the upcoming high-power laser facilities. Applications of high intensity γ-ray beams are also discussed.

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. In this paper 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.