arXiv subjects

P. Hadjisolomou

Publications and source records attributed to P. Hadjisolomou.

10 recordsLinked to original sources

arXiv2025

Injection and Acceleration of Electrons by Radially Polarized Laser Pulses in a Plasma Channel

We consider injection and subsequent acceleration of electrons in narrow plasma channels irradiated by linearly and radially polarized ultraintense laser pulses. Using three-dimensional particle-in-cell simulations, we show that radially polarized beams significantly promote electron release from the channel walls and lead to enhanced injection. We compare an f/10 linearly polarized laser beam with two radially polarized cases: one focused more tightly (f/5) to match peak intensity, and one at equal f/10 to capture polarization effects. The radially polarized f/10 case injects approximately one-third more charge than the linearly polarized case, while the f/5 radially polarized case outperforms the linearly polarized one by about a factor of two in terms of maximum electron energy. These results highlight polarization and focusing geometry as key parameters for optimizing laser-driven electron acceleration setups.

physics.plasm-ph↗

arXiv2025

Bright polarised x-ray flashes from dense plasmas

Creating a plasma dominated by strong-field QED (SFQED) effects is a major goal of new multi-PW laser facilities. This is motivated by the fact that the fundamental dynamics of such plasmas is poorly understood and plays an important role in the electrodynamics of extreme astrophysical environments such as pulsar magnetospheres. The most obvious observable for which such a regime has been reached is the production of a bright flash of x-rays, but distinguishing this from other sources of hard x-rays (e.g., bremsstrahlung) is a major challenge. Here we show that the photons from the X-ray flash are highly polarised, as compared to the unpolarised background, i.e., polarisation is an indicator that the SFQED plasma has really produced. For a laser of intensity $10^{21}$ Wcm$^{-2}$ impinging on a solid Al target, the photons of the flash with energy $>10$\thinspace keV are $>65\%$ polarised.

physics.plasm-ph↗

arXiv2024

Collimated $ \gamma $-flash emission along the target surface irradiated by a laser at non-grazing incidence

The interaction of a high-power laser with a solid target provides ways to produce beams of $\gamma$-photons. For normal incidence of the laser on the target the beams usually appear in a form of two lobes, which are symmetric with respect to the laser propagation axis. In this work we demonstrate via three-dimensional particle-in-cell simulations a regime where for oblique incidence the emission of a collimated $\gamma$-photon beam is in the direction parallel to the target surface. The process is ascribed to the interference pattern in the electromagnetic field formed by the incident and reflected laser pulse. The electromagnetic field accelerates electrons to the GeV energy level, while temporarily directing their momentum along the target surface. Consequently, they emit a collimated $\gamma$-photon beam in the same direction. The dependencies of $\gamma$-photon emission on the incident angle, laser pulse polarization, power and duration and target thickness and preplasma are also addressed in the paper. The beam directionality is important for designing future experiments. In addition, this setup causes the generation of high-order harmonics propagating along the target surface.

physics.plasm-ph↗

arXiv2024

Demonstration of The Brightest Nano-size Gamma Source

Gamma rays selectively interact with nuclei, induce and mediate nuclear reactions and elementary particle interactions, and exceed x-rays in penetrating power and thus are indispensable for analysis and modification of dense objects. Yet, the available gamma sources lack sufficient power and brightness. The predicted and highly desirable laser-driven gamma flash, from here on termed "Gamma Flash", based on inverse Compton scattering from solid targets at extreme irradiances (>$10^{23}W/cm^2$), would be the highest-power and the brightest terrestrial gamma source with a 30-40% laser-to-gamma energy conversion. However, Gamma Flash remains inaccessible experimentally due to the Bremsstrahlung background. Here we experimentally demonstrate a new interaction regime at the highest effective irradiance where Gamma Flash scaled quickly with the laser power and produced several times the number of Bremsstrahlung photons. Simulations revealed an attosecond, Terawatt Gamma Flash with a nanometre source size achieving a record brightness exceeding $~10^{23}photons/mm^2mrad^2s$ per 0.1% bandwidth at tens of MeV photon energies, surpassing astrophysical Gamma Ray Bursts. These findings could revolutionize inertial fusion energy by enabling unprecedented sub-micrometre/femtosecond resolution radiography of fuel mixing instabilities in extremely-compressed targets. The new gamma source could facilitate significant advances in time-resolved nuclear physics, homeland security, nuclear waste management and non-proliferation, while opening possibilities for spatially-coherent gamma rays.

physics.plasm-ph↗

arXiv2024

Attosecond gamma-ray flashes and electron-positron pairs in dyadic laser interaction with micro-wire

The interaction of an ultra-intense laser with matter is an efficient source of high-energy particles, with efforts directed towards narrowing the divergence and simultaneously increasing the brightness. In this paper we report on emission of highly collimated, ultrabright, attosecond $\gamma$-photons and generation of dense electron-positron pairs via a tunable particle generation scheme which utilizes the interaction of two high-power lasers with a thin wire target. Irradiating the target with a radially polarized laser pulse first produces a series of high charge, short duration, electron bunches with low transverse momentum. These electron bunches subsequently collide with a counter-propagating high intensity laser. Depending on the intensity of the counter-propagating laser, the scheme generates highly collimated ultra-bright GeV-level $\gamma$-beams and/or electron-positron plasma of solid density level.

physics.plasm-ph↗

arXiv2023

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 $γ$-photon generation when an intense laser beam interacts with matter, mainly via inverse Compton scattering at the high intensity limit. $γ$-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 $γ$-photon energy conversion using various target and/or laser field configurations. The aim of the present manuscript is to discuss several recently proposed $γ$-ray flash generation schemes, as a guide for upcoming $γ$-photon related experiments and for further evolution of the presently available theoretical schemes.

physics.plasm-ph↗

arXiv2021

Gamma-Ray Flash in the Interaction of a Tightly Focused Single-Cycle Ultraintense Laser Pulse with a Solid Target

We employ the $λ^3$ regime where a near-single-cycle laser pulse is tightly focused, thus providing the highest possible intensity for the minimal energy at a certain laser power. The quantum electrodynamics processes in the course of the interaction of the ultraintense laser with a solid target are studied via three-dimensional particle-in-cell simulations, revealing the generation of copious $γ$-photons and electron-positron pairs. The parametric study on the laser polarisation, target thickness and electron number density shows that the radially polarised laser provides the optimal regime for $γ$-photon generation. By varying the laser power in the range of 1 to 300 petawatt we find the scaling of the laser to $γ$-photon energy conversion efficiency. The laser-generated $γ$-photon interaction with a high-Z target is further studied by using Monte Carlo simulations revealing further electron-positron pair generation and radioactive nuclides creation.

physics.plasm-ph↗

arXiv2020

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 is given to targets with complex geometries aiming on 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-holes and central-hole length combinations is performed with 2-dimensional particle-in-cell simulations for polyethylene targets and a laser intensity of 5.2x10^21 W cm^-2. 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 ~40 MeV 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.

physics.plasm-ph↗

arXiv2019

Optimisation of Thin Plastic Foil Targets for Production of Laser-Generated Protons in the GeV Range

In order to realistically simulate the interaction of a femtosecond laser pulse with a nanometre-thick target it is necessary to consider a target preplasma formation due to the nanosecond long amplified-spontaneous-emission pedestal and/or prepulse. The relatively long interaction time dictated that hydrodynamic simulations should be employed to predict the target particles' number density distributions prior the arrival of the main laser pulse. By using the output of the hydrodynamic simulations as input into particle-in-cell simulations, a detailed understanding of the complete laser-foil interaction is achieved. Once the laser pulse interacts with the preplasma it deposits a fraction of its energy on the target, before it is either reflected from the critical density surface or transmitted through an underdense plasma channel. A fraction of hot electrons is ejected from the target leaving the foil in a net positive potential, which in turn results in proton and heavy ion ejection. In this work protons reaching ~25 MeV are predicted for a laser of ~40 TW peak power and ~600 MeV are expected from a ~4 PW laser system.

physics.plasm-ph↗

arXiv2018

Ultrashort PW laser pulse interaction with target and ion acceleration

We present the experimental results on ion acceleration by petawatt femtosecond laser solid interaction and explore strategies to enhance ion energy. The irradiation of micrometer thick (0.2 - 6.0 micron) Al foils with a virtually unexplored intensity regime (8x10^19 W/cm^2 - 1x10^21 W/cm^2) resulting in ion acceleration along the rear and the front surface target normal direction is investigated. The maximum energy of protons and carbon ions, obtained at optimised laser intensity condition (by varying laser energy or focal spot size), exhibit a rapid intensity scaling as I^0.8 along the rear surface target normal direction and I^0.6 along the front surface target normal direction. It was found that proton energy scales much faster with laser energy rather than the laser focal spot size. Additionally, the ratio of maximum ion energy along the both directions is found to be constant for the broad range of target thickness and laser intensities. A proton flux is strongly dominated in the forward direction at relatively low laser intensities. Increasing the laser intensity results in the gradual increase in the backward proton flux and leads to almost equalisation of ion flux in both directions in the entire energy range. These experimental findings may open new perspectives for applications.

physics.plasm-ph↗