Abstract
A pair of techniques have been developed for performing time-resolved X-ray microdiffraction on irreversible phase transformations. In one technique capillary optics are used to focus a high-flux broad-spectrum X-ray beam to a 60 µm spot size and a fast pixel array detector is used to achieve temporal resolution of 55 µs. In the second technique the X-rays are focused with Kirkpatrick-Baez mirrors to achieve a spatial resolution better than 10 µm and a fast shutter is used to provide temporal resolution better than 20 µs while recording the diffraction pattern on a (relatively slow) X-ray CCD camera. Example data from experiments are presented where these techniques are used to study self-propagating high-temperature synthesis reactions in metal laminate foils.
Highlights
Time-resolved X-ray diffraction is widely used for studying structural changes in materials
In this paper we describe a pair of recent X-ray diffraction experiments with temporal and spatial resolution around 15– 50 ms and 10–50 mm, respectively
In the first experiment we describe, conducted at the Cornell High Energy Synchrotron Source (CHESS), we achieved the necessary temporal resolution with a fast detector and the necessary spatial resolution by focusing the X-rays with capillary optics
Summary
Time-resolved X-ray diffraction is widely used for studying structural changes in materials. One can apply a pump–probe technique to irreversible transformations in a single-shot mode, using a suitably long pulse; by repeating the experiment on multiple specimens with various delays between pump and probe pulses a complete picture of the transformation sequence can be developed This approach relies on the transformation occurring very repeatably with respect to the pump signal timing, with the uncertainty being smaller than the desired temporal resolution (width) of the probe pulse. A different type of time-resolved X-ray experiment operates on longer time scales and treats the X-ray beam as a continuous source of photons In these experiments suitable temporal resolution can be achieved in one of two ways. While reactive multilayer foils present an exceptional opportunity to investigate localized transformations under extreme heating rates, the techniques we outline here are general and can be applied to other systems requiring similar spatial resolution or temporal resolution (or both) for X-ray scattering studies
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