Light intensification towards the Schwinger limit

A method to generate ultrahigh intense electromagnetic fields is suggested, based on the laser pulse compression, carrier frequency upshift, and focusing by a counterpropagating breaking plasma wave, relativistic flying parabolic mirror. This method allows us to achieve the quantum electrodynamics critical field (Schwinger limit) with present-day laser systems.     

Electron-positron pair production by electromagnetic pulses

Electron-positron pair production in vacuum by a single focused laser pulse and by two counter-propagating colliding focused pulses is analyzed. A focused laser pulse is described using a realistic three-dimensional model based on an exact solution of Maxwell’s equations. In particular, this model reproduces an important property of focused beams, namely, the existence of two types of waves with a transverse electric or magnetic vector (e-or h-polarized wave, respectively). The dependence of the number of produced pairs on the radiation intensity and focusing parameter is studied. It has been shown that the number of pairs produced in the field of a single e-polarized pulse is many orders of magnitude larger than that for an h-polarized pulse. The pulse-intensity dependence of the number of pairs produced by a single pulse is so sharp that the total energy of pairs produced by the e-polarized pulse with intensity near the intensity I _S = 4.65 × 10²⁹ W/cm² characteristic of QED is comparable with the energy of the pulse itself. This circumstance imposes a natural physical bound on the maximum attainable intensity of a laser pulse. For the case of two colliding circularly polarized pulses, it is shown that pair production becomes experimentally observable when the intensity of each beam is I ～ 10²⁶ W/cm², which is one to two orders of magnitude lower than that for a single pulse.     

Impact of kinetic processes on the macroscopic nonlinear evolution of the electromagnetic-beam-plasma instability

We present a new, fully kinetic mechanism of generation of spatial magnetic vortices that results from the resonant wave-particle interaction in a plasma. This phenomenon is of basic theoretical interest. It can be responsible for the magnetic vortices observed in numerical simulations in the wake of an ultrastrong, ultraintense laser pulse in an underdense plasma.     

Regimes of laser plasma expansion at optical breakdown in the normal atmosphere

Propagation regimes of a plasma (fast ionization wave, laser-supported radiation wave, and laser-supported detonation wave) generated by laser radiation in a wide range of intensities (5 × 10⁸?10¹¹ W/cm² ) are described. The regimes were analyzed on the basis of the calculated dependence of the propagation velocity on the laser radiation intensity. The lower bound of the velocity was used for the fast ionization wave. Calculation results agree with experimental data and show that the plasma propagates as a fast ionization wave in the above range of intensities.     

Relativistic electromagnetic solitons in the electron-ion plasma

We present the results of the investigation about the ion motion influence on relativistic soliton structure, and show that in the case of moving multinode solitons the effect of the ion dynamics results in the limiting of its amplitude. The constraint on the maximum amplitude corresponds to either the ion motion breaking in the low-node-number case, or to the electron trajectory self-intersection in the case of high-node-number solitons. The soliton breaking leads to the generation of fast ions, and provides a novel mechanism for the ion acceleration in the plasma irradiated by the high-intensity laser pulses.     

Monoisotopic varieties of silicon and germanium with a high chemical and isotopic purity

We presented the results on the preparation of high-purity monoisotopic varieties of silicon and germanium. The process involves the separation of isotopes in the form of SiF₄ and GeH₄ by centrifugation, ultrapurification of volatile compounds, and preparation of poly and single crystals. The attained degree of isotopic and chemical purities of single crystals obtained was shown. The content of the main isotope in the single crystals of ²⁸Si is >99.99% and those in the single crystals of ²⁹Si and ³⁰Si are >99.9%. The specific resistivity of the ²⁸Si single crystals is ～1 kOhm cm and those of ²⁹Si and ³⁰Si are about 100–150 Ohm cm. The samples of the ⁷⁶Ge single crystals have the main isotope content of >88 at.% and the difference concentration of electrochemically active impurities of 5·10¹⁰ cm^?3. The main isotope content in the ⁷⁴Ge polycrystal is 99.93 at.%. The optical and thermophysical properties of the isotope-enriched silicon and germanium single crystals were measured, which suggest a significant effect of the isopotic composition on thermal capacity, thermal conductivity, luminiscence, and light absorption.     

Ensemble of ultra-high intensity attosecond pulses from laser-plasma interaction

The efficient generation of intense X-rays and γ-radiation is studied. The scheme is based on the relativistic mirror concept, i.e., a flying thin plasma slab interacts with a counterpropagating laser pulse, reflecting part of it in the form of an intense ultra-short electromagnetic pulse having an up-shifted frequency. In the proposed scheme a series of relativistic mirrors is generated in the interaction of the intense laser with a thin foil target as the pulse tears off and accelerates thin electron layers. A counterpropagating pulse is reflected by these flying layers in the form of an ensemble of ultra-short pulses resulting in a significant energy gain of the reflected radiation due to the momentum transfer from flying layers.