arXiv subjects

Jonathan C. Wood

Publications and source records attributed to Jonathan C. Wood.

4 recordsLinked to original sources

arXiv2026

Observation of quantum effects on radiation reaction in strong fields

Radiation reaction, the force experienced by an accelerated charge due to radiation emission, has long been the subject of extensive theoretical and experimental research. Experimental verification of a quantum, strong-field description of radiation reaction is fundamentally important, and has wide-ranging implications for astrophysics, laser-driven particle acceleration, next-generation particle colliders and inverse-Compton photon sources for medical and industrial applications. However, the difficulty of accessing regimes where strong field and quantum effects dominate inhibited previous efforts to observe quantum radiation reaction in charged particle dynamics with high significance. We report the first high significance (> 5σ) observation of strong-field radiation reaction on electron spectra where quantum effects are substantial. We obtain the first, quantitative, strong evidence favouring the quantum-continuous and quantum-stochastic models over the classical model; the quantum models perform comparably. The lower electron energy losses predicted by the quantum models accounts for their improved performance. Model comparison was performed using a novel Bayesian framework which has widespread utility for laser-particle collision experiments, including those utilising conventional accelerators, where some collision parameters cannot be measured directly.

hep-ph↗

arXiv2022

Stability of ionisation-injection-based laser-plasma accelerators

Laser-plasma acceleration (LPA) is a compact technique to accelerate electron bunches to highly relativistic energies, making it a promising candidate to power radiation sources for industrial or medical applications. We report on the generation of electron beams from an 80 MeV-level LPA setup based on ionisation injection (II) over a duration of 8 hours at a repetition rate of 2.5 Hz, resulting in 72,000 consecutive shots with charge injection and acceleration. Over the full operation time the moving averages of the total beam charge of 14.5 pC and the charge between 70-80 MeV did not drift on a detectable level. The largest source of shot-to-shot jitter was in the beam charge (26% standard deviation), which was most strongly correlated with fluctuations in the plasma density (3.6% standard deviation). Particle-in-cell simulations demonstrate that this was chiefly caused by stronger laser self-focusing in higher density plasmas, which significantly increased the ionised charge along with the emittance of the beam. The nonlinearity of this process imposes tight constraints on the reproducibility of the laser-plasma conditions required for a low jitter II-LPA output if self-focusing plays a role in the laser evolution.

physics.acc-ph↗

arXiv2018

Laser wakefield acceleration with high-power, few-cycle mid-IR lasers

The study of laser wakefield electron acceleration (LWFA) using mid-IR laser drivers is a promising path for future laser driven electronaccelerators, when compared to traditional near-IR laser drivers uperating at 0.8-1 μm central wavelength (λlaser), as the necessary vector potential a_0 for electron injection can be achieved with smaller laser powers due to the linear dependence on λlaser. In this work, we perform 2D PIC simulations on LWFA using few-cycle high power (5-15 TW) laser systems with λlaser ranging from 0.88-10 μm. Such few-cycle systems are currently under development, aiming at Gas High Harmonics Generation applications where the favourable λlaser^2 scaling extends the range of XUV photon energies. We keep a_0 and n_e/n_cr (n_e being the plasma density and n_cr being the critical density for each λlaser) as common denominators in outr simulations, allowing for comparisons between drivers of different λlaser, with respect to the accelerated electron beam energy, charge, and conversion efficiency. While the electron energies are mainly dominated by the plasma dynamics, the laser to electron beam energy conversion efficiency shows significant enhancement with longer wavelength laser drivers.

physics.plasm-ph↗

arXiv2017

Highly efficient angularly resolving x-ray spectrometer optimized for absorption measurements with collimated sources

Highly collimated betatron radiation from a laser wakefield accelerator is a promising tool for spectroscopic measurements. Therefore there is a requirement to create spectrometers suited to the unique properties of such a source. We demonstrate a spectrometer which achieves an energy resolution of < 5 eV at 9 keV and is angularly resolving the x-ray emission allowing the reference and spectrum to be recorded at the same time. The single photon analysis is used to significantly reduce the background noise. Theoretical performance of various configurations of the spectrometer is calculated by a ray-tracing algorithm. The properties and performance of the spectrometer including the angular and spectral resolution are demonstrated experimentally on absorption above the K-edge of a Cu foil backlit by laser-produced betatron radiation x-ray beam.

physics.ins-det↗