Tantalum at extreme temperatures and pressures

Industrial processes use high power lasers to remove layers of material through a process known as ablation. This enables precise engineering of features on the material surface down to the nanometre scale. Normally high power optical or UV lasers are used in this process however scientific research facilities, such as the European XFEL [1], can now produce extremely short and high-energy pulses of x-rays which cause ablation in even the toughest materials, such as tantalum.

Further information

Unlike the case for ablation with optical laser pulses, the physics of x-ray ablation is poorly understood. This is, in part, because the processes which lead to damage occur much faster than experimentalists can probe. To understand more we must turn to large-scale molecular dynamics simulations, which trace the movement of every atom in a small region of the sample as it undergoes x-ray irradiation. This enables the temperature and pressure within the sample to be calculated on very small time scales, leading up to the point where it becomes damaged.

These simulations led to a prediction of the laser fluence (energy divided by area) at which tantalum is damaged by high energy x-rays, and an improved understanding of the damage process. These results will be of interest to industry given the use of tantalum in the manufacture of jet engines and in chemical engineering processes, as well as to fundamental materials science where the behaviour of materials is explored at increasingly extreme temperatures and pressures.

This study was conducted in collaboration with the University of Oxford and was funded by AWE. The simulations were run using the Eddie supercomputer maintained by the Edinburgh Compute and Data Facility, and the Slurm supercomputing cluster provided by the School of Physics and Astronomy.

"We are extremely grateful for access to these facilities, as even with supercomputers the simulations can take up to a week to probe a small sample (up to 1 micron thick) to moderate times (~400 picoseconds). The output files contain the locations of the 10s of millions of atoms at each time step in the simulation and therefore generate enormous amounts of data. We used DataStore to store hundreds of GB of simulation data and SharePoint to share the simulation files, analysis, and documentation with our collaborators. All publication data was collected using PURE." (Matthew Duff)

The Digital Research Services employed were the following:

• SharePoint - To share simulation files with collaborators
• Eddie - To conduct analysis, together with the School of Physics and Astronomy supercomputer cluster - Slurm
• DataStore - To store the huge amount of data generated in this study
• Pure - To collect all publication data

Dr Matthew Duff is a Post-Doctoral Research Associate in the School of Physics and Astronomy at the University of Edinburgh, and a member of the Institute for Condensed Matter and Complex Systems.

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• Poder, Kristjan, et al. "Experimental signatures of the quantum nature of radiation reaction in the field of an ultraintense laser." Physical Review X 8.3 (2018): 031004.
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• Duff, Matthew J., et al. "Modelling the effects of the radiation reaction force on the interaction of thin foils with ultra-intense laser fields." Plasma Physics and Controlled Fusion 60.6 (2018): 064006.

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