Session NM9: Mini-Conference on Laser-Matter Interactions: The Next Generation I

Strong field physics enabled by a 100 PW laser

A 100 PW laser can support focal intensities beyond 10$^{\mathrm{23}}$W/cm$^{\mathrm{2}}$, which will drive the interaction into the strong relativistic regime and create QED-featured plasma. In the former, charged particles can be accelerated to the unprecedented GeV to tens-of-GeV level via laser-driven wakefield acceleration. The concept of laser-driven table-tap accelerators can be significantly advanced. Further, interaction in the near-QED regime will exhibit exotic new effects such as gamma photons emission, radiation-reaction effect and QED cascade. A most exciting prospect is combining a 100 PW laser with a hard X-ray free-electron laser (XFEL) facility. It will lead the chasing on the discovering vacuum birefringence-a prominent strong field QED effect of vacuum. The proposed scientific activities and experimental design are introduced for a 100 PW laser system.   

Laser-Plasma experiments at ELI-NP

Recent advances in ultra-high power lasers architecture brings unprecedented intensity and pressure regimes within our reach. Extreme Light Infrastructure -- Nuclear Physics (ELI--NP) is a new large laser facility, part of the ELI European research infrastructure that will benefit from these upgrades in the next years. It has the ambitious goal to use extreme electromagnetic fields generated by two 10 PW laser beams for a broad range of research topics in fundamental physics at the frontier of plasma physics, nuclear physics and astrophysics, together with applied research in materials and life sciences. Here we describe the facility implementation status and challenges and the commissioning experiments related with laser-plasma interaction. Rom. Rep. Phys. 68, ELI-NP Technical Design Reports (2016).   

High-intensity research infrastructure at ELI Beamlines

The L4 laser (10 PW, 150 fs) at ELI Beamlines is expected to provide focused intensities approaching $10^{23}~{\rm W/cm^2}$ and thus herald a new era of research in ultra-high intensity laser matter interaction. This talk will describe the progress in enabling the associated technological infrastructure - including the laser system, beam transport, diagnostics and the experimental chamber~[1]. Synergistic experimental and theoretical programs are also developing tools for such research. The talk will also briefly describe these research areas like development of dedicated diagnostic equipment, efforts toward obtaining ultra-high intensities using tight-focusing and theoretical modeling toward future experiments where radiation reaction in the classical and quantum regime and pair production start to play an important role.\\ \\ {P3}S. Weber {\it et al.} Matter and Radiation at Extremes, 1-28 (2017), in press, \url{http://dx.doi.org/10.1016/j.mre.2017.03.003}.   

Experimental observation of strong radiation reaction in the field of an ultra-intense laser

Describing radiation reaction in an electromagnetic field is one of the most fundamental outstanding problems in electrodynamics [1]. It consists of determining the dynamics of a charged particle fully taking into account self-forces (loosely referred to as radiation reaction) resulting from the radiation fields generated by the particle whilst it is accelerated. Radiation reaction has only been invoked to explain the radiative properties of powerful astrophysical objects, such as pulsars and quasars [2]. From a theoretical standpoint, this phenomenon is subject of fervent debate [1, 3] and this impasse is worsened by the lack of experimental data, due to extremely high fields required to trigger these effects. Here, we report on the first experimental evidence of strong radiation reaction during the interaction of an ultra-relativistic electron beam with an intense laser field, beyond a purely classical description. \bigskip \\ $[1]$ R. T. Hammond et al., Phys. Rev. A 81, 062104 (2010). \\ $[2]$ R. Ruffini et al., Phys. Rep. 487, 1 (2010). \\ $[3]$ A. Di Piazza et al., Rev. Mod. Phys. 84, 1177 (2012).   

Ultra-bright GeV photon source via controlled electromagnetic cascades in laser-dipole waves

The prospect of achieving conditions for triggering strong-field QED phenomena at upcoming large-scale laser facilities raises a number of intriguing questions. What kind of new effects and interaction regimes can be accessed by basic QED phenomena? What are the minimal (optimal) requirements to trigger these effects and enter these regimes? How can we, from this, gain new fundamental knowledge or create important applications? The talk will concern the prospects of producing high fluxes of GeV photons by triggering a special type of self-sustaining cascade in the field of several colliding laser pulses that form a dipole wave [Gonoskov {\it et al.} arXiv:1610.06404 (2016)]. Apart from reaching the highest field strength for a given total power of laser pulses, the dipole wave enables anomalous radiative trapping that favors pair production and high-energy photon generation. An extensive theoretical analysis and 3D QED-PIC simulations indicate that the concept is feasible at upcoming large-scale laser facilities of 10 PW level and can provide an extraordinary intense source of GeV photons for novel experimental studies in nuclear and quark-nuclear physics.   

Extreme states of electron-positron plasma in multi-petawatt laser fields

The next generation of high-intensity laser facilities, such as ELI and XCELS, will allow reaching intensities sufficient for triggering strong-field QED phenomena. In particular, dense electron-positron-pair plasma can be created through vacuum breakdown by means of QED cascades. We analyze theoretically different nonlinear regimes of electron-positron plasma dynamics in multi-beam laser fields. First, we show that for laser powers of up to 20 PW QED-plasma with extraordinary high particle densities and fluxes, as well as ultra-bright bursts of GeV photons are produced. This could serve for unique sources of intense gamma rays and dense antimatter. This regime is governed by a current instability, which causes transformation of small plasma density perturbations into thin sheets with extreme current. Second, at higher laser powers created QED-plasma enters a self-compression stage driven by the generated magnetic field and reaches unprecedented pair densities on a short time scale. We call this regime a pinch regime and attribute such complex dynamics to inherent interaction of QED-plasma currents produced by counter-streaming electrons and positrons.   

Impact of extreme laser-driven magnetic fields on photon emission and electron acceleration

Newly constructed facilities such as ELI are expected to deliver unprecedented laser intensities. A solid density matter irradiated at these intensities will be able to generate strong currents and, as a result, sustain previously inaccessible in laboratory magnetic fields. We have examined the conditions required for the magnetic field generation and the impact that this magnetic field has on photon emission and electron acceleration in the presence of an ultra-intense laser pulse. Generation of extreme quasi-static magnetic fields can ultimately offer an extra “control knob” for exploring QED effects in experiments with high-intensity lasers.   

Gamma beams generation with high intensity lasers for two photon Breit-Wheeler pair production

Linear Breit-Wheeler pair creation is the lowest threshold process in photon-photon interaction, controlling the energy release in Gamma Ray Bursts and Active Galactic Nuclei, but it has never been directly observed in the laboratory. Using numerical simulations, we demonstrate the possibility to produce collimated gamma beams with high energy conversion efficiency using high intensity lasers and innovative targets. When two of these beams collide at particular angles, our analytical calculations demonstrate a beaming effect easing the detection of the pairs in the laboratory. This effect has been confirmed in photon collision simulations using a recently developed innovative algorithm. An alternative scheme using Bremsstrahlung radiation produced by next generation high repetition rate laser systems is also being explored and the results of first optimization campaigns in this regime will be presented.   

Simulations On Pair Creation In Collision Of $\gamma$-Beams Produced With High Intensity Lasers

Direct production of electron-positron pairs in two photon collisions, the Breit-Wheeler process, is one of the most basic processes in the universe[1]. However, this process has never been directly observed in the laboratory due to the lack of high intensity $\gamma$ sources[2]. For a feasibility study and for the optimisation of experimental set-ups[3] we developed a high-performance tree-code. Different possible set-ups with MeV photon sources were discussed and compared using collision detection for huge number of particles in a quantum-electrodynamic regime. For this we implemented bounding volume hierarchies in a tree-like code structure. We applied this code on the question whether the Texas Petawatt laser[5] could produce a significant number of pairs within the framework of the NSF project National Science Foundation under Grant No. 1632777.\\ \hfill \newline References: [1] Ruffini, R. \textit{et al.} Physics Reports {\bf 487}, 1-140 (2010). [2] Bamber C. et al. Phys. Rev. D, {\bf 60}, 092004 (1999). [3] X. Ribeyre \textit{et al.}, Phys. Rev. E {\bf 93}, 013201 (2016). [4] C. Ericson, Real Time Collision Detection, CRC Press, New York, (2005). [5] Gaul \textit{et al.}, Tech. Digest (Opti. Soc. of America, 2005), {\bf JFB2}.