arXiv subjects

Ou Z. Labun

Publications and source records attributed to Ou Z. Labun.

13 recordsLinked to original sources

arXiv2026

Laser-Wakefield-Driven Photonuclear and Laser-Driven DD Fusion Neutron Sources for Fast Neutron Capture: A Start-to-End Simulation Study

Laser-driven neutron sources offer ultrashort pulse durations and extreme peak fluxes inaccessible to conventional facilities, enabling novel time-of-flight(TOF) spectroscopy and nuclear astrophysics measurements. We present the first complete start-to-end simulation comparison of deuterium-deuterium (DD) bulk fusion and laser wakefield acceleration-driven photonuclear neutron sources, evaluated for fast neutron capture relevant to the r-process. The simulation chain couples particle-in-cell modeling of the laser-plasma interaction, Geant4 Monte Carlo neutron transport with shielding and background characterization, and a NON-SMOKER-based event generator for multi-neutron capture on Au197 and Rh103. We derive scaling laws for neutron yield, pulse duration, and peak flux from 1J terawatt to 250J petawatt-class systems, including DD bulk fusion scaling laws specific to the short-pulse regime where volumetric ion heating via plasma expansion timescales governs yield. Under realistic experimental conditions, DD fusion produces quasi-monoenergetic 2.45MeV neutrons with less than 20ps pulses, 100 micro source size, and peak fluxes exceeding 10^22 cm^(-2) s^(-1), ideal for high-resolution TOF spectroscopy. LWFA sources generate broader spectra with larger than 50ps pulses, but high repetition rates (up to 100 Hz) yield a 36x advantage in cumulative capture events for short-lived isomers. We conclude these sources are complementary: DD fusion maximizes per-shot peak brightness, while LWFA provides high-throughput accumulation for systematic studies. These results establish design criteria for the first direct laser-driven rapid neutron capture experiments at facilities including PHELIX, ELI-NP, and TW-class systems such as UT3.

physics.plasm-ph↗

arXiv2026

Scaling Interferometry to the Multi-Petawatt Regime

Pre-plasma conditions strongly influence laser-plasma interactions in the multi-petawatt (MPW) regime, increasing the need for reliable early-time plasma evolution diagnostics. Among available pre-plasma diagnostics, interferometry remains the most direct method for measuring the spatially resolved electron density of pre-formed plasmas. However, its implementation becomes increasingly challenging at MPW scale dueto steep density gradients, phase-recovery difficulties, strong electromagnetic pulses (EMP), debris accumulation, and high-repetition-rate operation. Compounding these technical challenges, many large-scale facilities lack permanent probe-line architecture and trained diagnostic support, reducing experimental reproducibility and consuming limited beamtime. Future MPW facilities should standardize probe-line architecture, adopt off frequency probing strategies, improve phase-recovery methods for non-symmetric plasmas, integrate emerging real-time analysis capabilities, and engineer diagnostic systems resilient to EMP and high-repetition-rate environments. These advances will enable the user community to reliably characterize pre-plasma formation and laser-plasma dynamics at next-generation MPW facilities.

physics.plasm-ph↗

arXiv2025

Unified Model of Heated Plasma Expansion

Motivated by the need to predict plasma density and temperature distributions created in the early stages of high-intensity laser-plasma interactions, we develop a fluid model of plasma expansion into vacuum that incorporates external heating. We propose a new three-parameter family of self-similar solutions for plasma expansion that models a wide range of spatiotemporal variations of the electron temperature. Depending on the relative scales of the heated plasma domain $L$, the Debye length $\lambda_D$ and an emergent ion-acoustic correlation length $\lambda_s$, characterized by the parameters $\frac{\lambda_s}{\lambda_D}$ and $\frac{L}{\lambda_s}$, a spectrum of dynamical behaviors for the expanding plasma are identified. The behavior is classified into five dynamical regimes, ranging from nearly quasineutral expansion to the formation of bare ion slabs susceptible to Coulomb explosion. Self-similar solutions with spatially uniform electron temperature with exponential time dependence are analyzed, and the dynamics in the five asymptotic limits in the parameter space are detailed. Scaling relations for the length scales and energies of the expanding plasma are proposed. The self-similar framework is applied to laser-plasma interactions, specifically addressing the plasma dynamics at a target surface as the target interacts with the rising laser intensity envelope. The results offer insights into the expansion behavior based on the laser-plasma parameters, and scaling relations for optimizing laser-plasma schemes and guiding experimental designs in high-intensity laser experiments.

physics.plasm-ph↗

arXiv2024

Performance envelope of laser wakefield accelerators

Laser wakefield accelerator experiments have made enormous progress over the past $\sim 20$ years, but their promise to revolutionize high-energy particle sources is only beginning to be realized. To make the next step toward engineering LWFAs for different accelerator outcomes, we need more reliable and quantitative models to predict performance. Using the data from $>50$ published experiments, we estimate scalings and the performance envelope. We compare the observed scalings with several models in the literature. We find that the total beam energy (centroid energy times beam charge) scales almost linearly with laser energy, supporting the value of investment in progressively higher energy driver lasers. The dataset includes pulse durations from 8 to 160 fs, but only laser wavelengths of 800 nm and 1 \si{\micro\meter}, meaning we could not check proposed wavelength scalings for alternative laser technologies. As a benchmark next-generation case, the observed scalings suggest that achieving a 100-GeV LWFA stage will require a $\gtrsim 30$ PW laser operating at electron density $<10^{17}/$cm$^3$.

physics.acc-ph↗

arXiv2023

Luminosity for laser-electron colliders

High intensity laser facilities are expanding their scope from laser and particle-acceleration test beds to user facilities and nuclear physics experiments. A basic goal is to confirm long-standing predictions of strong-field quantum electrodynamics, but with the advent of high-repetition rate laser experiments producing GeV-scale electrons and photons, novel searches for new high-energy particle physics also become possible. The common figure of merit for these facilities is the invariant $χ\simeq 2γ_e|\vec E_{\rm laser}|/E_c$ describing the electric field strength in the electron rest frame relative to the ``critical'' field strength of quantum electrodynamics where the vacuum decays into electron-positron pairs. However, simply achieving large $χ$ is insufficient; discovery or validation requires statistics to distinguish physics from fluctuations. The number of events delivered by the facility is therefore equally important. In high-energy physics, luminosity quantifies the rate at which colliders provide events and data. We adapt the definition of luminosity to high-intensity laser-electron collisions to quantify and thus optimize the rate at which laser facilities can deliver strong-field QED and potentially new physics events. Modeling the pulsed laser field and electron bunch, we find that luminosity is maximized for laser focal spot size equal or slightly larger than the diameter of the dense core of the electron bunch. Several examples show that luminosity can be maximized for parameters different from those maximizing the peak value of $χ$ in the collision. The definition of luminosity for electron-laser collisions is straightforwardly extended to photon-laser collisions and lepton beam-beam collisions.

hep-ph↗

arXiv2022

High-charge 10 GeV electron acceleration in a 10 cm nanoparticle-assisted hybrid wakefield accelerator

In an electron wakefield accelerator, an intense laser pulse or charged particle beam excites plasma waves. Under proper conditions, electrons from the background plasma are trapped in the plasma wave and accelerated to ultra-relativistic velocities. We present recent results from a proof-of-principle wakefield acceleration experiment that reveal a unique synergy between a laser-driven and particle-driven accelerator: a high-charge laser-wakefield accelerated electron bunch can drive its own wakefield while simultaneously drawing energy from the laser pulse via direct laser acceleration. This process continues to accelerate electrons beyond the usual decelerating phase of the wakefield, thus reaching much higher energies. We find that the 10-centimeter-long nanoparticle-assisted wakefield accelerator can generate 340 pC, 10.4+-0.6 GeV electron bunches with 3.4 GeV RMS convolved energy spread and 0.9 mrad RMS divergence. It can also produce bunches with lower energy, a few percent energy spread, and a higher charge. This synergistic mechanism and the simplicity of the experimental setup represent a step closer to compact tabletop particle accelerators suitable for applications requiring high charge at high energies, such as free electron lasers or radiation sources producing muon beams.

physics.plasm-ph↗

arXiv2021

Creating QED Photon Jets with Present-Day Lasers

Large-scale, relativistic particle-in-cell simulations with quantum electrodynamics (QED) models show that high energy (1$<E_γ\lesssim$ 75 MeV) QED photon jets with a flux of $10^{12}$ sr$^{-1}$ can be created with present-day lasers and planar, unstructured targets. This process involves a self-forming channel in the target in response to a laser pulse focused tightly ($f$ number unity) onto the target surface. We show the self-formation of a channel to be robust to experimentally motivated variations in preplasma, angle of incidence, and laser stability, and present in simulations using historical shot data from the Texas Petawatt. We estimate that a detectable photon flux in the 10s of MeV range will require about 60 J in a 150 fs pulse.

physics.plasm-ph↗

arXiv2020

Reconciling vacuum laser acceleration theory and experiment

The classical theory of single-electron dynamics in focused laser pulses is the foundation of both the relativistic ponderomotive force (RPF), which in turn underlies models of laser-collective-plasma dynamics, and the discovery of novel strong-field radiation dynamics. Despite this bedrock importance, consensus eludes the community as to whether acceleration of single electrons in vacuum has been observed in experiment. We analyze the experiment of Malka et al. (1998) with respect to several features that were neglected in modeling and that can restore consistency between theory predictions and experimental data. The right or wrong pulse profile function, laser parameters, or initial electron distribution each can make or break the agreement between predictions and data. The laser phase at which the electron's interaction with the pulse begins has a large effect, explaining why much larger energies are achieved by electrons liberated in the focal region by photoionization from high-Z atoms and by electrons ejected from a plasma mirror. Finally we estimate the error in a typical electron spectrum arising from fluctuating focal spot size in state-of-the-art ultra-relativistic laser facilities. Our results emphasize the importance of thoroughly characterizing laser parameters in order to achieve quantitatively accurate predictions and the precision required for discovery science.

physics.plasm-ph↗

arXiv2018

Jet Observable for Photons from High-Intensity Laser-Plasma Interactions

The goals of discovering quantum radiation dynamics in high-intensity laser-plasma interactions and engineering new laser-driven high-energy particle sources both require accurate and robust predictions. Experiments rely on particle-in-cell simulations to predict and interpret outcomes, but unknowns in modeling the interaction limit the simulations to qualitative predictions, too uncertain to test the quantum theory. To establish a basis for quantitative prediction, we introduce a `jet' observable that parameterizes the emitted photon distribution and quantifies a highly directional flux of high-energy photon emission. Jets are identified by the observable under a variety of physical conditions and shown to be most prominent when the laser pulse forms a wavelength-scale channel through the target. The highest energy photons are generally emitted in the direction of the jet. The observable is compatible with characteristics of photon emission from quantum theory. This work offers quantitative guidance for the design of experiments and detectors, offering a foundation to use photon emission to interpret dynamics during high-intensity laser-plasma experiments and validate quantum radiation theory in strong fields.

physics.plasm-ph↗

arXiv2017

Equality of hemisphere soft functions for $e^+e^-$, DIS and $pp$ collisions at $\mathcal{O}(α_s^2)$

We present a simple observation about soft amplitudes and soft functions appearing in factorizable cross sections in $ee$, $ep$, and $pp$ collisions that has not clearly been made in previous literature, namely, that the hemisphere soft functions that appear in event shape distributions in $e^+e^-\to$ dijets, deep inelastic scattering (DIS), and in Drell-Yan (DY) processes are equal in perturbation theory up to $\mathcal{O}(α_s^2)$, even though individual amplitudes may have opposite sign imaginary parts due to changing complex pole prescriptions in eikonal propagators for incoming vs. outgoing lines. We also explore potential generalizations of this observation to soft functions for other observables or with more jets in the final state.

hep-ph↗

arXiv2017

Rapidity regulators in the semi-inclusive deep inelastic scattering and Drell-Yan processes

We study the semi-inclusive limit of the deep inelastic scattering and Drell-Yan (DY) processes in soft collinear effective theory. In this regime so-called threshold logarithms must be resummed to render perturbation theory well behaved. Part of this resummation occurs via the Dokshitzer, Gribov, Lipatov, Altarelli, Parisi (DGLAP) equation, which at threshold contains a large logarithm that calls into question the convergence of the anomalous dimension. We demonstrate here that the problematic logarithm is related to rapidity divergences, and by introducing a rapidity regulator can be tamed. We show that resumming the rapidity logarithms allows us to reproduce the standard DGLAP running at threshold as long as a set of potentially large non-perturbative logarithms are absorbed into the definition of the parton distribution function (PDF). These terms could, in turn, explain the steep fall-off of the PDF in the endpoint. We then go on to show that the resummation of rapidity divergences does not change the standard threshold resummation in DY, nor do our results depend on the rapidity regulator we choose to use.

hep-ph↗

arXiv2016

Effective field theories for quantum chromo- and electrodynamics

In this dissertation, I introduce the principles and methods of effective field theory and describe my work in three EFTs: First, in the perturbative QCD region, I use soft collinear effective theory (SCET) to prove that strong interaction soft radiation is universal and to increase the QCD accuracy to next-to-next-tonext- to leading logarithm order for new particle searches in hadron colliders. I also compute a new class of non-perturbative, large logarithmic enhancement arising near the elastic limits of deep inelastic scattering and Drell-Yan processes. Second, in the QCD confinement region, I use heavy hadron chiral perturbation theory to study near-threshold enhancements in the scattering of $D$ and $π$ mesons near the threshold for the excited $D$-meson state, $D^*$, as well as in the scattering of $D$ and $D^*$ mesons near the threshold for the exotic hadron X(3872). This work provides a clear picture of the hadronic molecule X(3872) and more profound understanding of the nuclear force between hadrons. Finally, inspired by SCET, I construct a new electron-laser effective field theory to describe highly-relativistic electrons traveling in strong laser fields, extract the universal distribution of electrons in strong electromagnetic backgrounds and its evolution in energy from the separated momentum scales of emitted photons and classical radiation, and predict the rate of wide angle photon emission. I conclude with limitations of EFT methods and some perspectives on what new work may be achieved with these EFTs.

hep-ph↗

arXiv2015

Rapidity Divergences and Deep Inelastic Scattering in the Endpoint Region

The deep inelastic scattering cross section in the endpoint region, $x \sim 1$, has been subjected to extensive analysis. We revisit this process, and show that in the endpoint individual factors in the factorized hadronic tensor have rapidity divergences. We regulate these divergences using a recently introduced rapidity regulator, and find that each factor requires a different scale to minimize large rapidity logarithms. Interestingly, in this case running in rapidity is non-perturbative. In addition, we give an operator definition of the parton distribution function in the endpoint region, and remark on the issues that should be considered in constructing this function.

hep-ph↗