Gas gun shock experiments with single-pulse x-ray phase contrast imaging and diffraction at the Advanced Photon Source

Abstract

The highly transient nature of shock loading and pronounced microstructure effects on dynamic materials response call for in situ, temporally and spatially resolved, x-ray-based diagnostics. Third-generation synchrotron x-ray sources are advantageous for x-ray phase contrast imaging (PCI) and diffraction under dynamic loading, due to their high photon fluxes, high coherency, and high pulse repetition rates. The feasibility of bulk-scale gas gun shock experiments with dynamic x-ray PCI and diffraction measurements was investigated at the beamline 32ID-B of the Advanced Photon Source. The x-ray beam characteristics, experimental setup, x-ray diagnostics, and static and dynamic test results are described. We demonstrate ultrafast, multiframe, single-pulse PCI measurements with unprecedented temporal (<100 ps) and spatial (∼2 μm) resolutions for bulk-scale shock experiments, as well as single-pulse dynamic Laue diffraction. The results not only substantiate the potential of synchrotron-based experiments for addressing a variety of shock physics problems, but also allow us to identify the technical challenges related to image detection, x-ray source, and dynamic loading.

In situ damage assessment using synchrotron X-rays in materials loaded by a Hopkinson bar

“…2 µm) resolutions can be generated for capturing the dynamic events produced by impact loading from Hopkinson bars or shockwaves. Owing to the highly transient nature of shockwave experiments, even with the intensity level available at APS, it can still be quite challenging to obtain a series of X-ray images which track microstructural evolution during shock loading [27]. However, Hopkinson bar experiments have durations one to two orders of magnitude higher than shock experiments.…”

“…When the gap is increased from 20 to 30 mm, the fundamental (first harmonic) shifts from 9 to 13 keV, with peak broadening [27], which is accompanied by a decrease in photon number by a factor of three [27]. The fundamental of the X-rays used in our experiments was centred at roughly 9 keV, corresponding to an undulator gap of about 20 mm.…”

“…The spectrum characteristics of the X-ray beam are varied via altering the undulator gap [27], which was typically between 20 and 30 mm for the Hopkinson bar experiments. When the gap is increased from 20 to 30 mm, the fundamental (first harmonic) shifts from 9 to 13 keV, with peak broadening [27], which is accompanied by a decrease in photon number by a factor of three [27].…”

“…Proper experimental techniques must be introduced to enhance the contrast in the resultant images. In this study, we used X-ray phase contrast imaging (PCI) to enhance the interfaces between material phases or features inside the specimen on the imaging plane [27].…”

Microscale investigation of dynamic impact of dry and saturated glass powder

“…IMPULSE consists of a 12.6-mm bore light-gas gun with impact speeds up to 0.9 km/s. The multiframe X-ray PCI (MPCI) system consists of four separate ICCDs (Princeton Instruments PI-MAX 4) are optically coupled to a scintillator through a series of optical splitters, light tubes and objective lenses to result in a viewing area of 1.726 mm x 1.726 mm (see [9,10,11,12]) . The images capture light from a single photon bunch from the APS undulator and each camera may take two images during the course of an experiment (see Figure 1a, 1c and 1d).…”