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First HED experiment at XFEL

Professor Justin Wark

Professor of Physics

Sub department

  • Atomic and Laser Physics

Research groups

  • Oxford Centre for High Energy Density Science (OxCHEDS)
Justin.Wark@physics.ox.ac.uk
Telephone: 01865 (2)72251
Clarendon Laboratory, room 029.9
  • About
  • Publications

The study of shock-compressed condensed matter by use of advanced light sources

AIP Conference Proceedings AIP Publishing 3066:1 (2024) 440001
More details from the publisher

Exploring relaxation dynamics in warm dense plasmas by tailoring non-thermal electron distributions with a free electron laser

Physics of Plasmas AIP Publishing 31:8 (2024) 082305

Authors:

YuanFeng Shi, Shenyuan Ren, Hyun-kyung Chung, Justin Wark, Sam Vinko

Abstract:

Knowing the characteristic relaxation time of free electrons in a dense plasma is crucial to our understanding of plasma equilibration and transport. However, experimental investigations of electron relaxation dynamics have been hindered by the ultrafast, sub-femtosecond timescales on which these interactions typically take place. Here, we propose a novel approach that uses x rays from a free electron laser to generate well-defined non-thermal electron distributions, which can then be tracked via emission spectroscopy from radiative recombination as they thermalize. Collisional radiative simulations reveal how this method can enable the measurement of electron relaxation timescales in situ, shedding light on the applicability and accuracy of the Coulomb logarithm framework for modeling collisions in dense plasmas.
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Resonant inelastic x-ray scattering in warm-dense Fe compounds beyond the SASE FEL resolution limit

Communications Physics Nature Research 7:1 (2024) 266

Authors:

Alessandro Forte, Thomas Gawne, Karim K Alaa El-Din, Oliver S Humphries, Thomas R Preston, Céline Crépisson, Thomas Campbell, Pontus Svensson, Sam Azadi, Patrick Heighway, Yuanfeng Shi, David A Chin, Ethan Smith, Carsten Baehtz, Victorien Bouffetier, Hauke Höppner, Alexis Amouretti, David McGonegle, Marion Harmand, Gilbert W Collins, Justin S Wark, Danae N Polsin, Sam M Vinko

Abstract:

Resonant inelastic x-ray scattering (RIXS) is a widely used spectroscopic technique, providing access to the electronic structure and dynamics of atoms, molecules, and solids. However, RIXS requires a narrow bandwidth x-ray probe to achieve high spectral resolution. The challenges in delivering an energetic monochromated beam from an x-ray free electron laser (XFEL) thus limit its use in few-shot experiments, including for the study of high energy density systems. Here we demonstrate that by correlating the measurements of the self-amplified spontaneous emission (SASE) spectrum of an XFEL with the RIXS signal, using a dynamic kernel deconvolution with a neural surrogate, we can achieve electronic structure resolutions substantially higher than those normally afforded by the bandwidth of the incoming x-ray beam. We further show how this technique allows us to discriminate between the valence structures of Fe and Fe2O3, and provides access to temperature measurements as well as M-shell binding energies estimates in warm-dense Fe compounds.
More details from the publisher
Details from ORA
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Exploring relaxation dynamics in warm dense plasmas by tailoring non-thermal electron distributions with a free electron laser

(2024)

Authors:

Yuanfeng Shi, Shenyuan Ren, Hyun-kyung Chung, Justin S Wark, Sam M Vinko
More details from the publisher
Details from ArXiV

Bounds on heavy axions with an X-ray free electron laser

(2024)

Authors:

Jack WD Halliday, Giacomo Marocco, Konstantin A Beyer, Charles Heaton, Motoaki Nakatsutsumi, Thomas R Preston, Charles D Arrowsmith, Carsten Baehtz, Sebastian Goede, Oliver Humphries, Alejandro Laso Garcia, Richard Plackett, Pontus Svensson, Georgios Vacalis, Justin Wark, Daniel Wood, Ulf Zastrau, Robert Bingham, Ian Shipsey, Subir Sarkar, Gianluca Gregori
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