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Modeling of soft X-ray induced ablation in solids
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
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2011 (English)In: DAMAGE TO VUV, EUV, AND X-RAY OPTICS III, 2011, Vol. 8077Conference paper, Published paper (Refereed)
Abstract [en]

Powerful free electron lasers (FELs) operating in the soft X-ray regime are offering new possibilities for creating and probing materials under extreme conditions. We describe here simulations to model the interaction of a focused FEL pulse with metallic solids (niobium, vanadium, and their deuterides) at 13.5 nm wavelength (92 eV) with peak intensities between 10(15) to 10(18) W/cm(2) and a fixed pulse length of 15 femtoseconds (full width at half maximum). The interaction of the pulse with the metallic solids was modeled with a non-local thermodynamic equilibrium code that included radiation transfer. The calculations also made use of a self-similar isothermal fluid model for plasma expansion into vacuum. We find that the time-evolution of the simulated critical charge density in the sample results in a critical depth that approaches the observed crater depths in an earlier experiment performed at the FLASH free electron laser in Hamburg. The results show saturation in the ablation process at intensities exceeding 10(16) W/cm(2). Furthermore, protons and deuterons with kinetic energies of several keV have been measured, and these concur with predictions from the plasma expansion model. The results indicate that the temperature of the plasma reached almost 5 million K after the pulse has passed.

Place, publisher, year, edition, pages
2011. Vol. 8077
Series
Proceedings of SPIE, Volym 8077
Keyword [en]
X-ray free electron laser; plasma; ion acceleration; ablation; non - local thermodynamics equilibrium
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:uu:diva-169711DOI: 10.1117/12.888988OAI: oai:DiVA.org:uu-169711DiVA: diva2:507588
Conference
Conference on Damage to VUV, EUV, and X-ray Optics III
Note

Conference on Damage to VUV, EUV, and X-ray Optics III, Prague, CZECH REPUBLIC, APR 18-20, 2011

Available from: 2012-03-05 Created: 2012-03-05 Last updated: 2016-04-12
In thesis
1. Creating and Probing Extreme States of Materials: From Gases and Clusters to Biosamples and Solids
Open this publication in new window or tab >>Creating and Probing Extreme States of Materials: From Gases and Clusters to Biosamples and Solids
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Free-electron lasers provide high intensity pulses with femtosecond duration and are ideal tools in the investigation of ultrafast processes in materials. Illumination of any material with such pulses creates extreme conditions that drive the sample far from equilibrium and rapidly convert it into high temperature plasma. The dynamics of this transition is not fully understood and the main goal of this thesis is to further our knowledge in this area.

We exposed a variety of materials to X-ray pulses of intensities from 1013 to above 1017 W/cm2. We found that the temporal evolution of the resulting plasmas depends strongly on the wavelength and pulse intensity, as well as on material related parameters, such as size, density, and composition.

In experiments on atomic and molecular clusters, we find that cluster size and sample composition influence the destruction pathway. In small clusters a rapid Coulomb explosion takes place while larger clusters undergo a hydrodynamic expansion. We have characterized this transition in methane clusters and discovered a strong isotope effect that promotes the acceleration of deuterium ions relative to hydrogen. Our results also show that ions escaping from exploding xenon clusters are accelerated to several keV energies.

Virus particles represent a transition between hetero-nuclear clusters and complex biological materials. We injected single mimivirus particles into the pulse train of an X-ray laser, and recorded coherent diffraction images simultaneously with the fragmentation patterns of the individual particles. We used these results to test theoretical damage models. Correlation between the diffraction patterns and sample fragmentation shows how damage develops after the intense pulse has left the sample.

Moving from sub-micron objects to bulk materials gave rise to new phenomena. Our experiments with high-intensity X-ray pulses on bulk, metallic samples show the development of a transient X-ray transparency. We also describe the saturation of photoabsorption during ablation of vanadium and niobium samples.

Photon science with extremely strong X-ray pulses is in its infancy today and will require much more effort to gain more knowledge. The work described in this thesis represents some of the first results in this area.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 66 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 975
Keyword
free-electron laser, ultrashort X-rays, non-equilibrium plasma, Coulomb explosion, isotope effect, hydrodynamic expansion, ion acceleration, high intensity lasers, ablation, time-of-flight spectroscopy
National Category
Biophysics
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-180997 (URN)978-91-554-8477-4 (ISBN)
Public defence
2012-11-09, A1:107, Biomedical Center (BMC), Husargatan 3, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2012-10-17 Created: 2012-09-14 Last updated: 2013-01-23Bibliographically approved

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Caleman, CarlTimneanu, N.

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