Trips to synchrotron facilities could become a thing of the past for some researchers thanks to a new laboratory-scale three-dimensional X-ray diffraction microscope designed by a team from the University of Michigan, US. The device, which is the first of its kind, uses a liquid-metal-jet electrode to produce high-energy X-rays and can probe almost everything a traditional synchrotron can. It could therefore give a wider community of academic and industrial researchers access to synchrotron-style capabilities.
Synchrotrons are high-energy particle accelerators that produce bright, high-quality beams of coherent electromagnetic radiation at wavelengths ranging from the infrared to soft X-rays. To do this, they use powerful magnets to accelerate electrons in a storage ring, taking advantage of the fact that accelerated electrons emit electromagnetic radiation.
One application for this synchrotron radiation is a technique called three-dimensional X-ray diffraction (3DXRD) microscopy. This powerful technique enables scientists to study the mechanical behaviour of polycrystalline materials, and it works by constructing three-dimensional images of a sample from X-ray images taken at multiple angles, much as a CT scan images the human body. Instead of the imaging device rotating around a patient, however, it is the sample that rotates in the focus of the powerful X-ray beam.
At present, 3DXRD can only be performed at synchrotrons. These are national and international facilities, and scientists must apply for beamtime months or even years in advance. If successful, they receive a block of time lasting six days at the most, during which they must complete all their experiments.
A liquid-metal-jet anode
Previous attempts to make 3DXRD more accessible by downscaling it have largely been unsuccessful. In particular, efforts to produce high-energy X-rays using electrical anodes have foundered because these anodes are traditionally made of solid metal, which cannot withstand the extremely high power of electrons needed to produce X-rays.
The new lab-scale device developed by mechanical engineer Ashley Bucsek and colleagues overcomes this problem thanks to a liquid-metal-jet anode that can absorb more power and therefore produce a greater number of X-ray photons per electrode surface area. The sample volume is illuminated by a monochromatic box or line-focused X-ray beam while diffraction patterns are serially recorded as the sample rotates full circle. “The technique is capable of measuring the volume, position, orientation and strain of thousands of polycrystalline grains simultaneously,” Bucsek says.
When members of the Michigan team tested the device by imaging samples of titanium alloy samples, they found it was as accurate as synchrotron-based 3DXRD, making it a practical alternative. “I conducted my PhD doing 3DXRD experiments at synchrotron user facilities, so having full-time access to a personal 3DXRD microscope was always a dream,” Bucsek says. “My colleagues and I hope that the adaptation of this technology from the synchrotron to the laboratory scale will make it more accessible.”
The design for the device, which is described in Nature Communications, was developed in collaboration with a US-based instrumentation firm, PROTO Manufacturing. Bucsek says she is excited by the possibility that commercialization will make 3DXRD more “turn-key” and thus reduce the need for specialized knowledge in the field.
The Michigan researchers now hope to use their instrument to perform experiments that must be carried out over long periods of time. “Conducting such prolonged experiments at synchrotron user facilities would be difficult, if not impossible, due to the high demand, so, lab-3DXRD can fill a critical capability gap in this respect,” Bucsek tells Physics World.
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