Journal article
X-ray diffraction at the National Ignition Facility
- Abstract:
- We report details of an experimental platform implemented at the National Ignition Facility to obtain in situ powder diffraction data from solids dynamically compressed to extreme pressures. Thin samples are sandwiched between tamper layers and ramp compressed using a gradual increase in the drive-laser irradiance. Pressure history in the sample is determined using high-precision velocimetry measurements. Up to two independently timed pulses of x rays are produced at or near the time of peak pressure by laser illumination of thin metal foils. The quasi-monochromatic x-ray pulses have a mean wavelength selectable between 0.6 Å and 1.9 Å depending on the foil material. The diffracted signal is recorded on image plates with a typical 2θ x-ray scattering angle uncertainty of about 0.2° and resolution of about 1°. Analytic expressions are reported for systematic corrections to 2θ due to finite pinhole size and sample offset. A new variant of a nonlinear background subtraction algorithm is described, which has been used to observe diffraction lines at signal-to-background ratios as low as a few percent. Variations in system response over the detector area are compensated in order to obtain accurate line intensities; this system response calculation includes a new analytic approximation for image-plate sensitivity as a function of photon energy and incident angle. This experimental platform has been used up to 2 TPa (20 Mbar) to determine the crystal structure, measure the density, and evaluate the strain-induced texturing of a variety of compressed samples spanning periods 2–7 on the periodic table.
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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(Preview, Version of record, 5.6MB, Terms of use)
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- Publisher copy:
- 10.1063/1.5129698
Authors
- Publisher:
- AIP Publishing
- Journal:
- Review of Scientific Instruments More from this journal
- Volume:
- 91
- Issue:
- 4
- Article number:
- 043902
- Publication date:
- 2020-04-21
- Acceptance date:
- 2020-03-01
- DOI:
- EISSN:
-
1089-7623
- ISSN:
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0034-6748
- Language:
-
English
- Keywords:
- Pubs id:
-
1101055
- Local pid:
-
pubs:1101055
- Deposit date:
-
2020-04-23
Terms of use
- Copyright holder:
- Rygg et al.
- Copyright date:
- 2020
- Rights statement:
- © 2020 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
- Licence:
- CC Attribution (CC BY)
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