A. V. Korzhimanov

Ultrarelativistic nanoplasmonics as a route towards extreme-intensity attosecond pulses.

The generation of ultrastrong attosecond pulses through laser-plasma interactions offers the opportunity to surpass the intensity of any known laboratory radiation source, giving rise to new experimental possibilities, such as quantum electrodynamical tests and matter probing at extremely short scales. Here we demonstrate that a laser irradiated plasma surface can act as an efficient converter from the femto- to the attosecond range, giving a dramatic rise in pulse intensity. Although seemingly similar schemes have been described in the literature, the present setup differs significantly from the previous attempts. We present a model describing the nonlinear process of relativistic laser-plasma interaction. This model, which is applicable to a multitude of phenomena, is shown to be in excellent agreement with particle-in-cell simulations. The model makes it possible to determine a parameter region where the energy conversion from the femto- to the attosecond regime is maximal. Based on the study we propose a concept of laser pulse interaction with a target having a groove-shaped surface, which opens up the potential to exceed an intensity level of 10(26) W/cm(2) and observe effects due to nonlinear quantum electrodynamics with upcoming laser sources.

Relativistic self-induced transparency effect during ultraintense laser interaction with overdense plasmas: Why it occurs and its use for ultrashort electron bunch generation

A novel explanation of the relativistic self-induced transparency effect during superintense laser interaction with an overdense plasma is proposed. It was studied analytically and verified with direct modeling by particle-in-cell simulations. Based on this treatment, a method of ultrashort high-energy electron bunch generation with durations on a femtosecond time scale is also proposed and studied via numerical simulation.

Multicascade Proton Acceleration by a Superintense Laser Pulse in the Regime of Relativistically Induced Slab Transparency

The regime of multicascade proton acceleration during the interaction of a 10(21)-10(22) W/cm2 laser pulse with a structured target is proposed. The regime is based on the electron charge displacement under the action of laser ponderomotive force and on the effect of relativistically induced slab transparency which allows realization of the idea of multicascade acceleration. It is shown that a target comprising several thin foils properly spaced apart can optimize the acceleration process and give at the output a quasi-monoenergetic beam of protons with energies up to hundreds of MeV with an energy spread of just a few percent.

Particle-in-Cell Laser-Plasma Simulation on Xeon Phi Coprocessors

This paper concerns the development of a high-performance implementation of the Particle-in-Cell method for plasma simulation on Intel Xeon Phi coprocessors. We discuss the suitability of the method for Xeon Phi architecture and present our experience in the porting and optimization of the existing parallel Particle-in-Cell code PICADOR. Direct porting without code modification gives performance on Xeon Phi close to that of an 8-core CPU on a benchmark problem with 50 particles per cell. We demonstrate step-by-step optimization techniques, such as improving data locality, enhancing parallelization efficiency and vectorization leading to an overall 4.2 x speedup on CPU and 7.5 x on Xeon Phi compared to the baseline version. The optimized version achieves 16.9 ns per particle update on an Intel Xeon E5-2660 CPU and 9.3 ns per particle update on an Intel Xeon Phi 5110P. For a real problem of laser ion acceleration in targets with surface grating, where a large number of macroparticles per cell is required, the speedup of Xeon Phi compared to CPU is 1.6x.

Proton and light-ion acceleration to relativistic GeV energies by the superstrong laser radiation interacting with a structured plasma target

A new scheme is proposed for proton and light-ion acceleration to relativistic energies by superstrong laser radiation interacting with a structured plasma target. The proposal consists in the use of two-component targets consisting of heavy and light ions, where an ambipolar field is formed under the action of the ponderomotive force of incident radiation, and, in contrast to the traditional schemes, acceleration starts from the front boundary of the layer. It is shown that, for the optimized target parameters, monoenergetic GeV ion beams can be produced for radiation pulse intensities on the order of 1021−1022 W/cm2.

Interaction of relativistically strong electromagnetic waves with a layer of overdense plasma

Plasma-field structures that arise under the interaction between a relativistically strong electromagnetic wave and a layer of overdense plasma are considered within a quasistationary approximation. It is shown that, together with known solutions, which are nonlinear generalizations of skin-layer solutions, multilayer structures containing cavitation regions with completely removed electrons (ion layers) can be excited when the amplitude of the incident field exceeds a certain threshold value. Under symmetric irradiation, these cavitation regions, which play the role of self-consistent resonators, may amplify the field and accumulate electromagnetic energy.

Self-generated surface magnetic fields inhibit laser-driven sheath acceleration of high-energy protons

High-intensity lasers interacting with solid foils produce copious numbers of relativistic electrons, which in turn create strong sheath electric fields around the target. The proton beams accelerated in such fields have remarkable properties, enabling ultrafast radiography of plasma phenomena or isochoric heating of dense materials. In view of longer-term multidisciplinary purposes (e.g., spallation neutron sources or cancer therapy), the current challenge is to achieve proton energies well in excess of 100 MeV, which is commonly thought to be possible by raising the on-target laser intensity. Here we present experimental and numerical results demonstrating that magnetostatic fields self-generated on the target surface may pose a fundamental limit to sheath-driven ion acceleration for high enough laser intensities. Those fields can be strong enough (~105 T at laser intensities ~1021 W cm–2) to magnetize the sheath electrons and deflect protons off the accelerating region, hence degrading the maximum energy the latter can acquire.Laser-generated ion acceleration has received increasing attention due to recent progress in super-intense lasers. Here the authors demonstrate the role of the self-generated magnetic field on the ion acceleration and limitations on the energy scaling with laser intensity.

Experimental evidence for short-pulse laser heating of solid-density target to high bulk temperatures

Heating efficiently solid-density, or even compressed, matter has been a long-sought goal in order to allow investigation of the properties of such state of matter of interest for various domains, e.g. astrophysics. High-power lasers, pinches, and more recently Free-Electron-Lasers (FELs) have been used in this respect. Here we show that by using the high-power, high-contrast “PEARL” laser (Institute of Applied Physics-Russian Academy of Science, Nizhny Novgorod, Russia) delivering 7.5 J in a 60 fs laser pulse, such coupling can be efficiently obtained, resulting in heating of a slab of solid-density Al of 0.8 µm thickness at a temperature of 300 eV, and with minimal density gradients. The characterization of the target heating is achieved combining X-ray spectrometry and measurement of the protons accelerated from the Al slab. The measured heating conditions are consistent with a three-temperatures model that simulates resistive and collisional heating of the bulk induced by the hot electrons. Such effective laser energy deposition is achieved owing to the intrinsic high contrast of the laser which results from the Optical Parametric Chirped Pulse Amplification technology it is based on, allowing to attain high target temperatures in a very compact manner, e.g. in comparison with large-scale FEL facilities.

Low- and mid-Z ion acceleration by ultraintense femtosecond lasers in structured targets

The recent progress in theoretical investigation of ion acceleration by high-intensity lasers irradiating multicomponent structured targets will be presented with the emphasis on the possibility to produce monoenergetic beams of highly charged mid-Z ions.

Generation of giant attosecond pulses at the plasma surface in the regime of relativistic electronic spring

The generation of attosecond pulses with an amplitude greatly exceeding the driving field of an ultrarelativistic laser pulse at oblique irradiation of a solid target is investigated. We develop a universal model of the process, the so-called relativistic electronic spring, which is different from the conventional concept of an oscillating mirror. It follows from the model that there exists a parameter region where the energy conversion from the femto- to the attosecond regime is maximal. Based on the study we propose a new concept of laser pulse interaction with a target having a groove-shaped surface, which opens up the potential to exceed an intensity level of 1026 W/cm2 and observe effects due to nonlinear quantum electrodynamics with upcoming laser sources.