BEGIN:VCALENDAR VERSION:2.0 PRODID:-//linuxsoftware.nz//NONSGML Joyous v1.4//EN BEGIN:VEVENT SUMMARY:Atomic processes in XFEL-driven plasmas DTSTART:20250605T100000Z DTEND:20250605T120000Z DTSTAMP:20260610T055414Z UID:4891a2b4-de8c-4699-96ef-603d0a20281b SEQUENCE:1 CREATED:20250604T082813Z DESCRIPTION: Over the past two decades\, X-ray free-electron lasers (XFELs ) have made significant progress\, achieving peak brightness X-ray regions that were previously only attainable in the infrared. This has opened new possibilities in high-energy density science\, enabling the creation of s olid-density plasmas with larger volumes and better uniformity. XFEL heati ng proceeds through photoionisation and thermalisation\, initially creatin g non-thermal electron distributions\, offering a new platform for generat ing plasmas with tailored properties.We investigate the effects of inelast ic thermalisation in iron under intense X-ray irradiation using the atomic model BigBarT\, which evolves the electron distribution self-consistently . Our study focuses on collisional M-shell ionisation\, identified as the most efficient relaxation mechanism for non-thermal electrons. This could impact high-energy electron transport and points to the relevance of inclu ding atomic processes in kinetic models. Comparing calculated spectra with experimental data may also help refine collisional cross sections\, which are challenging to compute due to screening and continuum effects. We als o report the observation of the shake-off process in solid-density XFEL-pr oduced plasmas. Titanium foils were irradiated with XFEL pulses at 5.1 and 6 keV. Emission spectra show satellite features only at the higher energy \, consistent with the threshold for simultaneous K- and L-shell ionisatio n. These signatures are absent at lower energies and cannot be explained b y standard collisional or Auger ionisation mechanisms. LAST-MODIFIED:20250604T082813Z LOCATION:DF Seminar Room (2-8.3)\, 2nd floor of Physics Building URL:http://df.vps.tecnico.ulisboa.pt/en/events/atomic-processes-in-xfel-dr iven-plasmas/ X-ALT-DESC;FMTTYPE=text/html:

Over the past two decades\, X-ray free-electron lasers (XFELs) have made significant progres s\, achieving peak brightness X-ray regions that were previously only atta inable in the infrared. This has opened new possibilities in high-energy d ensity science\, enabling the creation of solid-density plasmas with large r volumes and better uniformity. XFEL heating proceeds through photoionisa tion and thermalisation\, initially creating non-thermal electron distribu tions\, offering a new platform for generating plasmas with tailored prope rties.


We investigate the effects of inelastic thermalisatio n in iron under intense X-ray irradiation using the atomic model BigBarT\, which evolves the electron distribution self-consistently. Our study focu ses on collisional M-shell ionisation\, identified as the most efficient r elaxation mechanism for non-thermal electrons.

This could impact high-energy electron transport and points to the relevance of including a tomic processes in kinetic models. Comparing calculated spectra with exper imental data may also help refine collisional cross sections\, which are c hallenging to compute due to screening and continuum effects.

We also report the observation of the shake-off process in solid-density XFE L-produced plasmas. Titanium foils were irradiated with XFEL pulses at 5.1 and 6 keV. Emission spectra show satellite features only at the higher en ergy\, consistent with the threshold for simultaneous K- and L-shell ionis ation. These signatures are absent at lower energies and cannot be explain ed by standard collisional or Auger ionisation mechanisms.

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