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

All-optical nonlinear Breit-Wheeler pair production with γ\gamma-flash photons

High-power laser facilities give experimental access to fundamental strong-field quantum electrodynamics processes. A key effect to be explored is the nonlinear Breit-Wheeler process: the conversion of high-energy photons into electron-positron pairs through the interaction with a strong electromagnetic field. A major challenge to observing nonlinear Breit-Wheeler pair production experimentally is first having a suitable source of high-energy photons. In this paper we outline a simple all-optical setup which efficiently generates photons through the so-called $\gamma$-flash mechanism by irradiating a solid target with a high-power laser. We consider the collision of these photons with a secondary laser, and systematically discuss the prospects for exploring the nonlinear Breit-Wheeler process at current and next-generation high-power laser facilities.Comment: 12 pages, 8 figure

The Effect of Ultrastrong Magnetic Fields on Laser-Produced Gamma-Ray Flashes

Laser produced $gamma$-photons can make an important impact on applied and fundamental physics that require high $gamma$-photon yield and strong collimation. We propose addition of a constant magnetic field to the laser-solid interaction to obtain the aforementioned desired $gamma$-photon properties. The $gamma$-ray flash spatial and spectral characteristics are obtained via quantum electrodynamics particle-in-cell simulations. When the constant magnetic field aligns with the laser magnetic field then the $gamma$-ray emission is significantly enhanced. Moreover, the $gamma$a-photon spatial distribution becomes collimated, approximately in the form of a disk.Comment: 5 pages, 5 figure

Towards laser ion acceleration with holed targets

Although the interaction of a flat foil with currently available laser intensities is now considered a routine process, during the last decade, emphasis has been given to targets with complex geometries aiming at increasing the ion energy. This work presents a target geometry where two symmetric side holes and a central hole are drilled into the foil. A study of the various side-hole and central-hole length combinations is performed with two-dimensional particle-in-cell simulations for polyethylene targets and a laser intensity of . The holed targets show a remarkable increase of the conversion efficiency, which corresponds to a different target configuration for electrons, protons and carbon ions. Furthermore, diffraction of the laser pulse leads to a directional high energy electron beam, with a temperature of , or seven times higher than in the case of a flat foil. The higher conversion efficiency consequently leads to a significant enhancement of the maximum proton energy from holed targets

Superluminal-subluminal orbital angular momentum femtosecond laser focus

The interplay between the frequency chirping of a broadband laser pulse and the longitudinal chromatic aberration of a focusing optic introduces the superluminal or subluminal behavior to a laser focus. In this paper, we present an analytic expression for an electric field describing a superluminal or subluminal femtosecond laser focus with orbital angular momentum. The analytic expression for a superluminal or subluminal laser focus is obtained through a diffraction integral, in which the focal length is replaced by a time-dependent focal length under the paraxial approximation, and the Fourier transformation. The speed and pulse duration of a laser focus are determined by the total group delay dispersion and a chromaticity parameter defined by the longitudinal chromatic aberration of a dispersive focusing optic. It is shown that it is possible to generate a several femtosecond superluminal orbital angular momentum laser focus in the focal region

Produkce elektron-pozitronových párů a radioaktivních jader ozařováním terče s vysokým protonovým číslem zábleskem γ fotonů generovaných ultraintenzivním laserem v režimu λ3

Tato práce studuje interakci laserem generovaných γ fotonů a vysokoenergetických nabitých částic s terči s vysokým protonovým číslem prostřednictvím simulací Monte Carlo. Interagující částice jsou převzaty z Particle in Cell simulace ultraintenzivního laserového pulsu úzce zaostřeného na titanový terč. Olovo je vybráno jako materiál sekundárního terče s vysokým protonovým číslem kvůli vysokému účinnému průřezu obří dipólové rezonance (z angl. Giant Dipole Resonance) a produkci elektron-pozitronového páru pomocí γ fotonů. Výsledky odhalují ultrakrátkou, ultrarelativistickou kolimovanou populaci pozitronů a jsou vypočítány a graficky znázorněny jejich energetická spektra, úhlová rozdělení a časové profily. Zkoumáme závislost výsledného celkového počtu a celkové kinetické energie různých druhů částic emitovaných z olověného terče ozářeného laserem generovanými γ fotony a nabitými částicemi zvlášť na tloušťce terče. Graficky interpretujeme množství zbytkových nuklidů s vysokým protonovým číslem, které vznikají při ozařování olověného terče. Vzhledem ke krátké době trvání pulzu by zdroje γ fotonů, elektron-pozitronových párů a neutronů mohly najít uplatnění v materiálových vědách, jaderné fyzice, laboratorní astrofyzice a jako injektory v laserových urychlovačích nabitých částic.This paper studies the interaction of laser-driven γ photons and high-energy charged particles with high-Z targets through Monte Carlo simulations. The interacting particles are taken from particle-in-cell simulations of the interaction of a tightly focused ultra-intense laser pulse with a titanium target. Lead is chosen as the secondary high-Z target because of its high cross-section of the giant dipole resonance and electron-positron pair production. The results reveal an ultra-short, ultra-relativistic collimated positron population, and their energy spectra, angular distribution, and temporal profile are found. We investigate the target thickness dependence of the resulting total numbers and total kinetic energies of various particle species emitted from the lead target irradiated with laser-generated γ photons and charged particles separately. We plot the charts of residual high-Z nuclides generated by irradiation of the lead target. Because of the short pulse duration, the γ photon, electron-positron, and neutron sources could find applications in material science, nuclear physics, laboratory astrophysics, and as injectors in laser-based accelerators of charged particles

Guided post-acceleration of laser-driven ions by a miniature modular structure

All-optical approaches to particle acceleration are currently attracting a significant research effort internationally. Although characterized by exceptional transverse and longitudinal emittance, laser-driven ion beams currently have limitations in terms of peak ion energy, bandwidth of the energy spectrum and beam divergence. Here we introduce the concept of a versatile, miniature linear accelerating module, which, by employing laser-excited electromagnetic pulses directed along a helical path surrounding the laser-accelerated ion beams, addresses these shortcomings simultaneously. In a proof-of-principle experiment on a university-scale system, we demonstrate post-acceleration of laser-driven protons from a flat foil at a rate of 0.5 GeV m(−1), already beyond what can be sustained by conventional accelerator technologies, with dynamic beam collimation and energy selection. These results open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications

High energy implementation of coil-target scheme for guided re-acceleration of laser-driven protons

Abstract Developing compact ion accelerators using intense lasers is a very active area of research, motivated by a strong applicative potential in science, industry and healthcare. However, proposed applications in medical therapy, as well as in nuclear and particle physics demand a strict control of ion energy, as well as of the angular and spectral distribution of ion beam, beyond the intrinsic limitations of the several acceleration mechanisms explored so far. Here we report on the production of highly collimated ( $$\sim 0.2^{\circ }$$ ∼ 0 . 2 ∘ half angle divergence), high-charge (10s of pC) and quasi-monoenergetic proton beams up to $$\sim$$ ∼ 50 MeV, using a recently developed method based on helical coil targetry. In this concept, ions accelerated from a laser-irradiated foil are post-accelerated and conditioned in a helical structure positioned at the rear of the foil. The pencil beam of protons was produced by guided post-acceleration at a rate of $$\sim$$ ∼ 2 GeV/m, without sacrificing the excellent beam emittance of the laser-driven proton beams. 3D particle tracing simulations indicate the possibility of sustaining high acceleration gradients over extended helical coil lengths, thus maximising the gain from such miniature accelerating modules

Dataset for "Dynamics of guided post-acceleration of protons in a laser-driven travelling-field accelerator"

Dataset underpinning the results presented in the article titled, "Dynamics of guided post-acceleration of protons in a laser-driven travelling-field accelerator" published in Plasma Physics and Controlled Fusion (2020) Abstract of the paper: By directing the laser-driven electromagnetic pulses along a helical path, one can achieve a travelling-field accelerator arrangement for simultaneous beam shaping and re-acceleration of laser-accelerated protons. The dynamics of guided acceleration of the transiting protons was studied by varying the length of the helical coil. Experimental data shows that the protons co-moving with the field region exhibit stronger focussing while increasing the coil length, with an increase of kinetic energy due to simultaneous post-acceleration. The net energy gain for a coil of constant pitch however saturates eventually when the post-accelerated protons overtakes the accelerating field region in due course. 3D particle tracing simulation underpins the dynamics of beam transport inside the coil, which highlights the requirement for a variable pitch coil geometry in order to sustain the post-acceleration over an extended coil