X-ray ptychography is an imaging technique that scans a sample through a coherent X-ray beam to collect diffraction information from overlapping regions, before reconstructing them into a high-resolution image. This technique produces quantitative phase images with the highest possible spatial resolutions, going well beyond the conventional limitations of the available X-ray optics, and has wide-reaching applications across the physical and life sciences. However, scanning techniques have inherent overheads, with the need to move sample stages and capture motor positions and detector frames. Ptychography has remained significantly slower than direct methods such as Transmission X-ray Microscopy (TXM) and Micro Computed Tomography (micro-CT), which limits its application to the wider scientific community. In work recently published in Scientific Reports, Diamond scientists detail steps they have taken to reduce the bottlenecks on the I13-1 beamline, making it the fastest ptychography beamline in the world. Faster scans enable the study of more dynamic and in-operando processes, increase the throughput of experiments and offer users real-time feedback.
Many synchrotron facilities offer X‐ray ptychography, a coherent scanning imaging technique that can produce high-resolution quantitative phase imaging at the nanoscale. X‐ray ptychography has much to offer across a range of different research fields, including energy, electronics, magnetism and life sciences. However, the scanning nature of ptychography means that it is slow compared to other imaging techniques.
Dr Darren Batey, senior beamline scientist on I13, said;
Theoretically, X‐ray ptychography offers the highest resolution, phase sensitivity, and dose efficiency. But the scanning overheads slow it down significantly, so it's not entirely delivering on its promise to the scientific community. What we've done on I13-1 is investigate how to remove these bottlenecks and drastically reduce the time taken for data collection.
One methodology for scanning techniques is similar to stop-motion animation. After a frame is recorded, everything moves a tiny amount, then stops for another frame to be taken. It's incredibly precise, but it's also slow. An alternative methodology is for everything to be in continuous motion, with snapshots taken at appropriate intervals. The new data acquisition strategy developed for I13-1 uses an up-triggering approach to match the maximum acquisition rate of the detector with slower controller and trigger boxes, exploiting the full capability of the detector recording rate of up to 9 kHz. The beamline team has used this approach to record and reconstruct a 9 kHz 2D scan and a 2 kHz 3D ptychographic tomography of a (20 μm)3 sample in less than three hours.
High-speed X-ray ptychography will allow users to study some dynamic processes and carry out in situ and in operando experiments. There are also the added benefits of being able to carry out more investigations during one beamtime allocation, improving statistical relevance, and receiving real-time feedback.
This new multi-kHz triggering scheme shifts the limiting factor of a ptychographic scan from the motors to the detector and coherent flux. For 3D scans, the volume and rate of data that needs to be written is now the limiting factor. The beamline is installing new hardware that will remove this bottleneck and bring the acquisition time for a 3D ptychography scan from hours to minutes. For example, the acquisition time for the 2 kHz 3D scan mentioned in the publication will go from 3 hours down to only 15 minutes – bringing the method in line with more conventional imaging methods.
Dr Batey explained;
The work we detail here is transforming the scientific throughput at I13-1 and made it the fastest X-ray ptychography beamline in the world. I13-1 is now limited by the amount of coherent flux produced by the X-ray source, which means that when the Diamond II upgrade comes online, we'll immediately see a bump in performance. We're continuing to work on improving the technique, the hardware, and accelerating the data processing pipelines to match. We are making great progress in these areas and look forward to reporting new capabilities in due course.
Dr Christoph Rau, Principal Beamline Scientist at I13 concludes;
This work is important for the I13 beamline’s multi-scale imaging capabilities. It closes the gap in recording speed between nano- and micro- imaging, enabling science across three orders in magnitude in resolution.
To find out more about the I13-1 beamline or discuss potential applications, please contact Principal Beamline Scientist Christoph Rau: christoph.rau@diamond.ac.uk.
Batey D et al. High-speed X-ray ptychographic tomography. Scientific Reports 12.1: 1-6 (2022). DOI:10.1038/s41598-022-11292-8.
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