Electron - positron cascades in multiple-laser optical traps

We present an analytical and numerical study of multiple-laser QED cascades induced with linearly polarised laser pulses. We analyse different polarisation orientations and propose a configuration that maximises the cascade multiplicity and favours the laser absorption. We generalise the analytical estimate for the cascade growth rate previously calculated in the field of two colliding linearly polarised laser pulses and account for multiple laser interaction. The estimate is verified by a comprehensive numerical study of four-laser QED cascades across a range of different laser intensities with QED PIC module of OSIRIS. We show that by using four linearly polarised 30 fs laser pulses, one can convert more than 50 % of the total energy to gamma-rays already at laser intensity $I\simeq10^{24}\ \mathrm{W/cm^2}$. In this configuration, the laser conversion efficiency is higher compared with the case with two colliding lasers

Spectral Line Shapes in Plasmas

International audienceFor the first two Spectral Line Shapes in Plasma workshops, participants submitted in total over 1,500 line-shape calculations. The studies collected in this Special Issue explore only a part of this immense work. This book is a reprint of the special issue that appeared in the online open access journal Atoms (ISSN 2218-2004) in 2014 (available at: http://www.mdpi.com/journal/atoms/special_issues/SpectralLineShapes)

Comparative study of semiclassical approaches to quantum dynamics

Quantum states can be described equivalently by density matrices, Wigner functions or quantum tomograms. We analyze the accuracy and performance of three related semiclassical approaches to quantum dynamics, in particular with respect to their numerical implementation. As test cases, we consider the time evolution of Gaussian wave packets in different one-dimensional geometries, whereby tunneling, resonance and anharmonicity effects are taken into account. The results and methods are benchmarked against an exact quantum mechanical treatment of the system, which is based on a highly efficient Chebyshev expansion technique of the time evolution operator.Comment: 32 pages, 8 figures, corrected typos and added references; version as publishe

SPIG2018

This Special Issue covers a wide range of topics from fundamental studies to applications of ionized gases. It is dedicated to four topics of interest: 1. ATOMIC COLLISION PROCESSES (electron and photon interactions with atomic particles, heavy particle collisions, swarms, and transport phenomena); 2. PARTICLE AND LASER BEAM INTERACTION WITH SOLIDS (atomic collisions in solids, sputtering and deposition, and laser and plasma interactions with surfaces); 3. LOW TEMPERATURE PLASMAS (plasma spectroscopy and other diagnostic methods, gas discharges, and plasma applications and devices); 4. GENERAL PLASMAS (fusion plasmas, astrophysical plasmas, and collective phenomena). This Special Issue of Atoms will highlight the need for continued research on ionized gas physics in different topics ranging from fundamental studies to applications, and will review current investigations

Quantum effects on radiation friction driven magnetic field generation

Radiation losses in the interaction of superintense circularly polarized laser pulses with high-density plasmas can lead to the generation of strong quasistatic magnetic fields via absorption of the photon angular momentum (so called inverse Faraday effect). To achieve the magnetic field strength of several Giga Gauss laser intensities $\simeq 10^{24}$W/cm$^2$ are required which brings the interaction to the border between the classical and the quantum regimes. We improve the classical modeling of the laser interaction with overcritical plasma in the "hole boring" regime by using a modified radiation friction force accounting for quantum recoil and spectral cut-off at high energies. The results of analytical calculations and three-dimensional particle-in-cell simulations show that, in foreseeable scenarios, the quantum effects may lead to a decrease of the conversion rate of laser radiation into high-energy photons by a factor 2-3. The magnetic field amplitude is suppressed accordingly, and the magnetic field energy - by more than one order in magnitude. This quantum suppression is shown to reach a maximum at a certain value of intensity, and does not grow with the further increase of intensities. The non monotonic behavior of the quantum suppression factor results from the joint effect of the longitudinal plasma acceleration and the radiation reaction force. The predicted features could serve as a suitable diagnostic for radiation friction theories.Comment: 10 pages, 3 figure