Tomoscopy Follows Fast Dynamic Processes

An inter­national research team at the Swiss Light Source SLS has set a new tomo­graphy world record using a rotary sample table developed at the Helmholtz Zentrum Berlin HZB. With 208 three-dimensional tomographic X-ray images per second, they were able to document the dynamic processes involved in the foaming of liquid aluminium. For this record, the precision rotary sample table designed at the HZB rotates around its axis at several hundred revo­lutions per second with extreme precision. The HZB team headed Francisco García-Moreno combined the rotary sample table with high-resolution optics and achieved a world record of over 25 tomo­graphic images per second using the BESSY II EDDI beamline in 2018.

The rotary sample table turns around its axis at several hundred revolutions per second with extreme precision. (Source: HZB)

Now the team, together with the group headed by Marco Stampanoni from the Paul Scherrer Institute PSI, has achieved a new world record. To accomplish this, they set up the rotary sample table at the SLS’s TOMCAT beamline. This has a high-speed camera with an extremely high data transfer rate, which was specially developed for such fast measure­ments. “Over 200 tomographic images per second can now be acquired – and that during measure­ment durations of several minutes”. Tomo­scopy was coined for this new imaging method.

Christian Schlepütz of PSI emphasises: “Each tomo­scopy generates huge amounts of data that have to be conti­nuously stored at the extremely high data rate of eight gigabytes per second. This is the only way to observe the extremely fast processes in the material over long periods of time.” Following the experiments, thousands of individual tomo­graphies have to be calculated from the measurement data on the computer clusters at PSI, and the images are auto­matically processed further, enabling quanti­tative analyses.

In order to handle the processing of several terabytes of data from each experiment, Paul Kamm from the HZB has developed and imple­mented unique dedicated processing software. The partners in this colla­boration have used the new imaging method to observe dynamic processes in great detail at high temporal reso­lution that occur during the foaming of liquid aluminium. In this way, processes taking place during the formation of foam in molten metals can be inves­tigated and better understood. This is important in order to achieve optimum material distri­bution and uniform pore formation in the foam, which is later cured, so that the foam can be used in lightweight con­struction.

Metal foams are an important class of materials for lightweight construction, and they are an advan­tageous subject of inves­tigation for the newly developed imaging method, since liquid metal is largely insen­sitive to radiation damage, and the imaging speeds achieved are extremely well-suited to foaming phenomena.

Computer tomoscopy could also provide interesting insights into many other processes. For example, it could be used to inves­tigate how materials change during laser welding or what happens when batteries overheat due to short circuits (thermal runaway). The researchers at the HZB and PSI are now working on increasing the rota­tional speed in order to further increase the temporal reso­lution of the measurements. (Source: HZB)

Reference: F. García-Moreno et al.: Using X-ray tomoscopy to explore the dynamics of foaming metal, Nat. Commun. 10, 3762 (2019); DOI: 10.1038/s41467-019-11521-1

Links: X-Ray Tomography Group, Paul Scherrer Institute, Villigen, Switzerland • Applied Materials Sciences, Helmholtz-Zentrum Berlin für Materialien und Energie HZB, Berlin, Germany


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