arXiv subjects

Eitan Y. Levine

Publications and source records attributed to Eitan Y. Levine.

6 recordsLinked to original sources

arXiv2026

Efficient dispersal of submicron solid particles for stratospheric aerosol injection

Stratospheric aerosol injection (SAI) using solid particles has been proposed as an alternative to sulfate aerosols for solar radiation modification, but practical deployment faces challenges in efficiently deagglomerating and dispersing powders as submicron particles. Here we experimentally demonstrate pneumatic dispersal of particles in optically optimal size ranges for SAI. Using spherical amorphous silica particles, we find that applying a hydrophobic surface treatment substantially improves dispersibility, with 50-85% of treated particle mass achieving submicron sizes compared to 10% for untreated particles. We compare the dispersal of treated particles of different sizes and find that 300 nm particles provide superior deagglomeration than 500 nm particles for the same air consumption. Theoretical modeling of the adhesion forces between particles, combined with surface roughness parameters extracted from atomic force microscopy, successfully predicted the relative dispersibility across different particle types. The pneumatic dispersal system achieved optimal performance at air-to-powder mass ratios of about 10:1. Using the measured dispersed particle sizes, we provide a scaling analysis suggesting that a feasibly sized fleet of dispersal aircraft could provide an aerosol layer sufficient for meaningful climate intervention. These results demonstrate that hydrophobic surface treatment and pneumatic dispersal can overcome the agglomeration challenge for SAI with solid particles.

physics.app-ph↗

arXiv2025

First direct observation of a wakefield generated with structured light

The use of structured light to control the phase velocity of the wake in laser-wakefield accelerators has generated significant interest for its ability to mitigate electron dephasing. Combining the diffraction-free properties of Bessel beams with spatio-temporal shaping of the pulse promises to enable acceleration with an unprecedented combination of long acceleration lengths and high gradients. This would facilitate the acceleration of electrons to energies above 100 GeV in existing laser facilities. In-depth understanding of the physical mechanisms involved is critical to achieving dephasing-free electron acceleration. Here we present the first experimental observation of wakefields generated by beams that were spatio-temporally sculpted and then focused with a long-focal-depth mirror, known as an axiparabola, which generates a quasi-Bessel beam. The resulting wakefield was imaged using femtosecond relativistic electron microscopy. Novel insights into this minimally explored regime include mapping the wakefield development over the focal depth and studying the effects of spatio-temporal manipulations of the beam on the structure and phase velocity of the wakefield. Such insights pave the way towards realizing the potential of structured-light based solutions to dephasing in laser-wakefield acceleration.

physics.acc-ph↗

arXiv2023

Use of spatiotemporal couplings and an axiparabola to control axial energy deposition velocity

This paper presents the first experimental realization of a scheme that allows for the tuning of the axial energy deposition velocity of a focal spot with relativistic intensity. By combining a tunable pulse-front curvature with the axial energy deposition characteristics of the axiparabola, an aspheric optical element, this system allows for controlling the dynamics of laser-wakefield accelerators. We demonstrate the ability to modify the axial energy deposition velocity of 100 TW laser pulses to be superluminal or subluminal. The experimental results are supported by theoretical calculations and simulations, strengthening the case for the axiparabola as a pertinent strategy to achieve dephasingless acceleration.

physics.optics↗

arXiv2022

Control of electron beam current, charge and energy spread using density downramp injection in laser wakefield accelerators

Density dowmramp injection has been demonstrated to be an elegant and efficient approach for generating high quality electron beams in laser wakefield accelerators. Yet, the charge of the produced beam is tens of pC per Joule of laser energy, still limiting its use for a wider range of applications. The possibility of generating high charge beam while keeping a good beam quality, stays to be explored. Moreover, despite previous studies focused on separate physical processes such as beam loading which affects the uniformity of the acceleration field and thus the energy spread of the trapped electrons, repulsive force from the rear spike of the bubble which reduces the transverse momentum $p_\perp$ of the trapped electrons and results in small beam emmittance, and the laser evolution when travelling in plasma. A more general investigation of the plasma density parameters on the final beam properties is required. In this work, we demonstrate that the current profile of the injected electron beam is directly correlated with the density transition parameters, which further affects the beam charge and energy spread. By fine-tuning the plasma density parameters, high-charge (up to several hundreds of pC) and low-energy-spread (around 1\% FWHM) electron beams can be obtained. All these results are supported by large-scale three-dimensional particle-in-cell simulations.

physics.plasm-ph↗

arXiv2022

Spatiotemporal pulse characterization with far-field beamlet cross-correlation

We present a novel, straightforward method for spatiotemporal characterization of ultra-short laser pulses. The method employs far-field interferometry and inverse Fourier transform spectroscopy, built on the theoretical basis derived in this paper. It stands out in its simplicity: it requires few non-standard optical elements and simple analysis algorithms. This method was used to measure the space-time intensity of our 100 TW class laser and to test the efficacy of a refractive doublet as a suppressor of pulse front curvature (PFC). The measured low-order spatiotemporal couplings agreed with ray-tracing simulations. In addition, we demonstrate a one-shot measurement technique, derived from our central method, which allows for quick and precise alignment of the compressor by pulse front tilt (PFT) minimization and for optimal refractive doublet positioning for the suppression of PFC.

physics.optics↗

arXiv2013

Impact of Colored Environmental Noise on the Extinction of a Long-Lived Stochastic Population: Role of the Allee Effect

We study the combined impact of a colored environmental noise and demographic noise on the extinction risk of a long-lived and well-mixed isolated stochastic population which exhibits the Allee effect. The environmental noise modulates the population birth and death rates. Assuming that the Allee effect is strong, and the environmental noise is positively correlated and Gaussian, we derive a Fokker-Planck equation for the joint probability distribution of the population sizes and environmental fluctuations. In WKB approximation this equation reduces to an effective two-dimensional Hamiltonian mechanics, where the most likely path to extinction and the most likely environmental fluctuation are encoded in an instanton-like trajectory in the phase space. The mean time to extinction (MTE) is related to the mechanical action along this trajectory. We obtain new analytic results for short-correlated, long-correlated and relatively weak environmental noise. The population-size dependence of the MTE changes from exponential for weak environmental noise to no dependence for strong noise, implying a greatly increased extinction risk. The theory is readily extendable to population switches between different metastable states, and to stochastic population explosion, due to a combined action of demographic and environmental noise.

q-bio.PE↗