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Atomic and Laser Physics
Credit: Jack Hobhouse

Dr Eva Los

PDRA Extreme Laboratory Astrophysics

Research theme

  • Particle astrophysics & cosmology
  • Lasers and high energy density science

Sub department

  • Atomic and Laser Physics

Research groups

  • Laboratory astroparticle physics
eva.los@physics.ox.ac.uk
Clarendon Laboratory, room Simon Room
  • About
  • Publications

A Bayesian framework to investigate radiation reaction in strong fields

High Power Laser Science and Engineering Cambridge University Press (CUP) 13 (2025) e25

Authors:

Eva E Los, Christopher Arran, Elias Gerstmayr, Matthew JV Streeter, Brendan Kettle, Zulfikar Najmudin, Christopher P Ridgers, Gianluca Sarri, Stuart PD Mangles

Abstract:

Abstract Recent experiments aiming to measure phenomena predicted by strong-field quantum electrodynamics (SFQED) have done so by colliding relativistic electron beams and high-power lasers. In such experiments, measurements of collision parameters are not always feasible. However, precise knowledge of these parameters is required to accurately test SFQED. Here, we present a novel Bayesian inference procedure that infers collision parameters that could not be measured on-shot. This procedure is applicable to all-optical non-linear Compton scattering experiments investigating radiation reaction. The framework allows multiple diagnostics to be combined self-consistently and facilitates the inclusion of known information pertaining to the collision parameters. Using this Bayesian analysis, the relative validity of the classical, quantum-continuous and quantum-stochastic models of radiation reaction was compared for several test cases, which demonstrates the accuracy and model selection capability of the framework and highlight its robustness if the experimental values of fixed parameters differ from their values in the models.
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Extended X-ray absorption spectroscopy using an ultrashort pulse laboratory-scale laser-plasma accelerator

Communications Physics Springer Nature 7:1 (2024) 247

Authors:

Brendan Kettle, Cary Colgan, Eva E Los, Elias Gerstmayr, Matthew JV Streeter, Felicie Albert, Sam Astbury, Rory A Baggott, Niall Cavanagh, Kateřina Falk, Timothy I Hyde, Olle Lundh, P Pattathil Rajeev, Dave Riley, Steven J Rose, Gianluca Sarri, Chris Spindloe, Kristoffer Svendsen, Dan R Symes, Michal Šmíd, Alec GR Thomas, Chris Thornton, Robbie Watt, Stuart PD Mangles

Abstract:

Laser-driven compact particle accelerators can provide ultrashort pulses of broadband X-rays, well suited for undertaking X-ray absorption spectroscopy measurements on a femtosecond timescale. Here the Extended X-ray Absorption Fine Structure (EXAFS) features of the K-edge of a copper sample have been observed over a 250 eV window in a single shot using a laser wakefield accelerator, providing information on both the electronic and ionic structure simultaneously. This capability will allow the investigation of ultrafast processes, and in particular, probing high-energy-density matter and physics far-from-equilibrium where the sample refresh rate is slow and shot number is limited. For example, states that replicate the tremendous pressures and temperatures of planetary bodies or the conditions inside nuclear fusion reactions. Using high-power lasers to pump these samples also has the advantage of being inherently synchronised to the laser-driven X-ray probe. A perspective on the additional strengths of a laboratory-based ultrafast X-ray absorption source is presented.
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Narrow bandwidth, low-emittance positron beams from a laser-wakefield accelerator.

Scientific reports 14:1 (2024) 6001

Authors:

MJV Streeter, C Colgan, J Carderelli, Y Ma, N Cavanagh, EE Los, H Ahmed, AF Antoine, T Audet, MD Balcazar, L Calvin, B Kettle, SPD Mangles, Z Najmudin, PP Rajeev, DR Symes, AGR Thomas, G Sarri

Abstract:

The rapid progress that plasma wakefield accelerators are experiencing is now posing the question as to whether they could be included in the design of the next generation of high-energy electron-positron colliders. However, the typical structure of the accelerating wakefields presents challenging complications for positron acceleration. Despite seminal proof-of-principle experiments and theoretical proposals, experimental research in plasma-based acceleration of positrons is currently limited by the scarcity of positron beams suitable to seed a plasma accelerator. Here, we report on the first experimental demonstration of a laser-driven source of ultra-relativistic positrons with sufficient spectral and spatial quality to be injected in a plasma accelerator. Our results indicate, in agreement with numerical simulations, selection and transport of positron beamlets containing N e + ≥ 10 5 positrons in a 5% bandwidth around 600 MeV, with femtosecond-scale duration and micron-scale normalised emittance. Particle-in-cell simulations show that positron beams of this kind can be guided and accelerated in a laser-driven plasma accelerator, with favourable scalings to further increase overall charge and energy using PW-scale lasers. The results presented here demonstrate the possibility of performing experimental studies of positron acceleration in a laser-driven wakefield accelerator.
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Effect of electron-beam energy chirp on signatures of radiation reaction in laser-based experiments

Physical Review Accelerators and Beams American Physical Society (APS) 26:10 (2023) 104002

Authors:

J Magnusson, TG Blackburn, E Gerstmayr, EE Los, M Marklund, CP Ridgers, SPD Mangles
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Laser wakefield accelerator modelling with variational neural networks

High Power Laser Science and Engineering Cambridge University Press (CUP) 11 (2023) e9

Authors:

MJV Streeter, C Colgan, CC Cobo, C Arran, EE Los, R Watt, N Bourgeois, L Calvin, J Carderelli, N Cavanagh, SJD Dann, R Fitzgarrald, E Gerstmayr, AS Joglekar, B Kettle, P Mckenna, CD Murphy, Z Najmudin, P Parsons, Q Qian, PP Rajeev, CP Ridgers, DR Symes, AGR Thomas, G Sarri, SPD Mangles
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