arXiv subjects

Ovidiu Tesileanu

Publications and source records attributed to Ovidiu Tesileanu.

7 recordsLinked to original sources

arXiv2026

On the generation of astrophysically-relevant intermittent magnetic turbulence in the laboratory

Intermittent magnetic turbulence, namely the presence of non-ordered and clusterized fields, is a ubiquitous phenomenon in space and astrophysical plasmas. It is currently understood that it plays a crucial role in the dynamics of astrophysical systems at all scales, from influencing the evolution of the cosmos as a whole to governing local particle acceleration. While there is direct evidence of turbulence in the solar wind, and despite progress obtained through multi-wavelength observations, most of our knowledge of it outside the solar system derives from indirect evidence, through modeling. Here we show that magnetic turbulence, that quantitatively matches that measured in space, can be reproduced in the laboratory. Starting from a homogeneous magnetized plasma, we randomly perturb it using a speckled laser beam. Using proton radiography, we can follow the development and quantitatively characterize the produced intermittent turbulence from its inception.

physics.plasm-ph↗

arXiv2026

Implementation and commissioning of an experimental system towards sub-eV axion-like particle searches with 0.1 PW laser at ELI-NP

We have developed and commissioned an experimental system at ELI-NP towards searches for axion-like particles (ALPs) in the worldwide 10~PW-class laser facility. The search principle is based on the Four-Wave Mixing (FWM) process at a focal region of coaxially combined two laser beams. The subsystems to control vacuum pressure, area size, spatiotemporal overlap and trigger-event pattern, are integrated into the experimental area for 0.1 PW laser output at ELI-NP. The integrated system is dedicated to identifying the possible background sources originated from the residual atoms and the optical elements. The performance and functionality of the subsystems were validated through the evaluations of laser characteristics, their stability and the FWM signal detections. Furthermore commissioning results for the background studies were demonstrated with 20 mJ-level laser pulses at the vacuum pressure of $1.3 \times 10^{-7}$ mbar. In conclusion, the integrated experimental system is fully functional as designed and provides a suitable platform for the background studies towards the ALP searches, enabling a stepwise scale-up of the laser pulse energies from 20 mJ to the maximum energy of 2.5 J in the 0.1 PW experimental area.

hep-ex↗

arXiv2025

Search for sub-eV axion-like particles in a quasi-parallel stimulated resonant photon-photon collider with "coronagraphy"

Axion-like particles (ALPs) have been searched for with a quasi-parallel stimulated resonant photon-photon collider sensitive to the sub-eV mass range by focusing two-color near-infrared pulse lasers into a vacuum. In this work, we have developed a specialized coronagraphy to mitigate the dominant background photons from optical elements by introducing an eclipse filter. The observed number of signal-like photons was found to be consistent with residual background photons from optical elements through an additional test by degrading the focal point overlapping factor between the two lasers. We then extended the exclusion region in the relation between ALP-photon coupling, $g/M$, and the ALP mass $m$, reaching the most sensitive point $g/M = 5.45\times10^{-7}\,\mathrm{GeV^{-1}}$ at $m = 0.15\,\mathrm{eV}$ for pseudoscalar ALPs.

hep-ex↗

arXiv2022

Search for sub-eV axion-like particles in a stimulated resonant photon-photon collider with two laser beams based on a novel method to discriminate pressure-independent components

Sub-eV axion-like particles (ALPs) have been searched for by focusing two-color near-infrared pulse lasers into a vacuum along a common optical axis. Within the focused quasi-parallel collision system created by combining a creation field ($2.5\,\mathrm{mJ}/47\,\mathrm{fs}$ Ti:Sapphire laser) and a background inducing field ($1.5\,\mathrm{mJ}/9\,\mathrm{ns}$ Nd:YAG laser), the detection of signal photons via stimulated resonant photon-photon scattering by exchanging ALPs was attempted in a vacuum chamber. The signal wavelength can be determined via energy-momentum conservation in the vacuum, and it coincides with that determined from the atomic four-wave-mixing (aFWM) process. In this work, the pulse energies were one order of magnitude higher than those in the previous search, allowing aFWM from optical elements to be observed as a pressure-independent background for the first time, in addition to the residual-gas-originating aFWM following a quadratic pressure dependence. In principle the four-wave-mixing process in vacuum via ALP exchanges (vFWM) must also be pressure-independent, so the development of a new method for discriminating the optical-element aFWM is indispensable for increasing the pulse energies to the values needed for future upgraded searches. In this paper, we will present the established method for quantifying the yield from the optical-element aFWM process based on the beam cross-section dependence. With the new method, the number of signal photons was found to be consistent with zero. We then successfully obtained a new exclusion region in the relation between ALP-photon coupling, $g/M$, and the ALP mass $m$, reaching the most sensitive point $g/M = 1.14\times10^{-5}\,\mathrm{GeV^{-1}}$ at $m = 0.18\,\mathrm{eV}$.

hep-ex↗

arXiv2021

Search for sub-eV axion-like resonance states via stimulated quasi-parallel laser collisions with the parameterization including fully asymmetric collisional geometry

We have searched for axion-like resonance states by colliding optical photons in a focused laser field (creation beam) by adding another laser field (inducing beam) for stimulation of the resonance decays, where frequency-converted signal photons can be created as a result of stimulated photon-photon scattering via exchanges of axion-like resonances. A quasi-parallel collision system (QPS) in such a focused field allows access to the sub-eV mass range of resonance particles. In past searches in QPS, for simplicity, we interpreted the scattering rate based on an analytically calculable symmetric collision geometry in both incident angles and incident energies by partially implementing the asymmetric nature to meet the actual experimental conditions. In this paper, we present new search results based on a complete parameterization including fully asymmetric collisional geometries. In particular, we combined a linearly polarized creation laser and a circularly polarized inducing laser to match the new parameterization. A 0.10 mJ / 31 fs Ti:sapphire laser pulse and a 0.20 mJ / 9 ns Nd:YAG laser pulse were spatiotemporally synchronized by sharing a common optical axis and focused into the vacuum system. Under a condition in which atomic background processes were completely negligible, no significant scattering signal was observed at the vacuum pressure of $2.6 \times 10^{-5}$ Pa, thereby providing upper bounds on the coupling-mass relation by assuming exchanges of scalar and pseudoscalar fields at a 95 % confidence level in the sub-eV mass range.

hep-ex↗

arXiv2017

High Flux Electron Beams from Laser Wakefield Accelerators Driven by Petawatt Lasers

Laser Wakefield Accelerator (LWFA) is considered as one of the most competitive candidates for the accelerators of the next generation. With the development of high power laser technologies, LWFA has shown its potential of replacing the conventional radio-frequency (RF) accelerators due to its flexibility and adjustability. In this paper, we will study the potential high flux electron beam productions of LWFA driven by petawatt-level laser pulses. In our three dimensional particle-in-cell simulations, an optimal set of parameters gives $\sim 40\ \rm nC$ of charge with $2\ \rm PW$ laser power, thus $\sim 400\ \rm kA$ of instantaneous current if we assume the electron beam duration is 100 fs. This high flux and its secondary radiation are widely applicable in nuclear and QED physics, industrial imaging, medical and biological studies.

physics.plasm-ph↗

arXiv2011

Numerical simulations of radiative magnetized Herbig-Haro jets: the influence of pre-ionization from X-rays on emission lines

We investigate supersonic, axisymmetric magnetohydrodynamic (MHD) jets with a time-dependent injection velocity by numerical simulations with the PLUTO code. Using a comprehensive set of parameters, we explore different jet configurations in the attempt to construct models that can be directly compared to observational data of microjets. In particular, we focus our attention on the emitting properties of traveling knots and construct, at the same time, accurate line intensity ratios and surface brightness maps. Direct comparison of the resulting brightness and line intensity ratios distributions with observational data of microjets shows that a closer match can be obtained only when the jet material is pre-ionized to some degree. A very likely source for a pre-ionized medium is photoionization by X-ray flux coming from the central object.

astro-ph.SR↗