Abstract
The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump-probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the FirstUser Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in theDAC.
Highlights
Generating high-pressure and high-temperature states of matter to better understand the dynamics of the interior of planetary bodies (Duffy et al, 2015) such as the Earth (Mao & Hemley, 2007), or to synthesize new materials for industrial applications (e.g. Bykov et al, 2018), has been an ongoing area of research for almost a century
One of the primary tools for creating these extreme conditions is the diamond anvil cell (DAC) which compresses a sample of interest between two opposing diamond anvils, while high temperatures may be induced through either heating internally, with infrared lasers, or externally, through the application of graphite or wire resistive heaters
Within this work we describe the experimental setup developed to conduct time-resolved X-ray diffraction (XRD) experiments with symmetric piston–cylinder DACs in interaction chamber 2 (IC2) of the High Energy Density (HED) instrument and its technical capabilities used during the First User Community Assisted Commissioning (1st UCAC; McWilliams, 2019)
Summary
Generating high-pressure and high-temperature states of matter to better understand the dynamics of the interior of planetary bodies (Duffy et al, 2015) such as the Earth (Mao & Hemley, 2007), or to synthesize new materials for industrial applications (e.g. Bykov et al, 2018), has been an ongoing area of research for almost a century. One of the major challenges encountered when studying reactive materials, in heated DACs, is the possible reaction of the sample of interest with other materials in the sample cavity, such as the pressure-transmitting medium, surrounding gasket material or carbon released from the diamonds (Prakapenka et al, 2003; Dewaele et al, 2010; Morard et al, 2018) These sample contaminations can result in significant discrepancies between data obtained in a DAC and those obtained using dynamic compression techniques such as gas guns and laser shock/ramp compression The EuXFEL offers high-energy X-ray pulses up to 25 keV at a repetition rate of up to 4.5 MHz with a peak brilliance that is 108 times higher than at any third-generation light source, with tight focusing to micrometre-scale beam spots These properties are ideal for probing small samples through thick diamond anvils, with optimized access to Q space through limited apertures, i.e. for XRD.
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