Gamma-Flash Generation in Multi-Petawatt Laser-Matter Interactions

The progressive development of high power lasers over the last several decades, enables the study of $\gamma$-photon generation when an intense laser beam interacts with matter, mainly via inverse Compton scattering at the high intensity limit. $\gamma$-ray flashes are a phenomenon of broad interest, drawing attention of researchers working in topics ranging from cosmological scales to elementary particle scales. Over the last few years, a plethora of studies predict extremely high laser energy to $\gamma$-photon energy conversion using various target and/or laser field configurations. The aim of the present manuscript is to discuss several recently proposed $\gamma$-ray flash generation schemes, as a guide for upcoming $\gamma$-photon related experiments and for further evolution of the presently available theoretical schemes.Comment: 12 pages, 8 figure

Towards Bright Gamma-Ray Flash Generation From Tailored Target Irradiated by Multi-Petawatt Laser

One of the remarkable phenomena in the laser-matter interaction is the extremely efficient energy transfer to $\gamma$-photons, that appears as a collimated $\gamma$-ray beam. For interactions of realistic laser pulses with matter, existence of a background field plays a crucial role, since it hits the target prior to the main pulse arrival, leading to a cloud of preplasma and drilling a narrow channel inside the target. These effects significantly alter the process of $\gamma$-photon generation. Here, we study this process by importing the outcome of magnetohydrodynamic simulations of the target interaction into particle-in-cell simulations for describing the $\gamma$-photon generation. It is seen that the background field effect plays an important positive role, enhancing the efficiency of laser pulse coupling with the target, and generating high energy electron-positron pairs. It is expected that such a $\gamma$-photon source will be actively used in various applications in nuclear photonics, material science and astrophysical processes modeling.Comment: 8 pages, 7 figure

Extreme plasma states in laser-governed vacuum breakdown

Triggering vacuum breakdown at the upcoming laser facilities can provide rapid electron-positron pair production for studies in laboratory astrophysics and fundamental physics. However, the density of the emerging plasma should seemingly stop rising at the relativistic critical density, when the plasma becomes opaque. Here we identify the opportunity of breaking this limit using optimal beam configuration of petawatt-class lasers. Tightly focused laser fields allow plasma generation in a small focal volume much less than ${\lambda}^3$, and creating extreme plasma states in terms of density and produced currents. These states can be regarded as a new object of nonlinear plasma physics. Using 3D QED-PIC simulations we demonstrate the possibility of reaching densities of more than $10^{25}$ cm$^{-3}$, which is an order of magnitude higher than previously expected. Controlling the process via the initial target parameters gives the opportunity to reach the discovered plasma states at the upcoming laser facilities

Contemporary particle-in-cell approach to laser-plasma modelling

Particle-in-cell (PIC) methods have a long history in the study of laser-plasma interactions. Early electromagnetic codes used the Yee staggered grid for field variables combined with a leapfrog EM-field update and the Boris algorithm for particle pushing. The general properties of such schemes are well documented. Modern PIC codes tend to add to these high-order shape functions for particles, Poisson preserving field updates, collisions, ionisation, a hybrid scheme for solid density and high-field QED effects. In addition to these physics packages, the increase in computing power now allows simulations with real mass ratios, full 3D dynamics and multi-speckle interaction. This paper presents a review of the core algorithms used in current laser-plasma specific PIC codes. Also reported are estimates of self-heating rates, convergence of collisional routines and test of ionisation models which are not readily available elsewhere. Having reviewed the status of PIC algorithms we present a summary of recent applications of such codes in laser-plasma physics, concentrating on SRS, short-pulse laser-solid interactions, fast-electron transport, and QED effects