Contact

Dr. Natalia Shevchenko

n.shevchenkoAthzdr.de
Phone: +49 351 260 3313

X-ray and neutron radiography

X-ray and neutron radiography are absorption-based imaging techniques [1, 2]. X-rays or neutron beams pass through the sample and are attenuated according to the composition or structure of the sample.

Figure 1: The measurement principle of radiography: the sample is irradiated and a detector screen behind the sample images the transmitted intensity distribution, which are typically visualised as grey-scale images.

The attenuation of X-ray or neutron beam is described by Beer-Lambert’s law (or the Beer-Lambert-Bouguer law). The transmittance I/I0 is defined as the ratio of the transmitted to incident intensity of the X-ray or neutron beam, and depends exponentially on the effective attenuation coefficient μ of the penetrated sample and its thickness x in the beam direction: I/ I0 = exp(-µ·x)

The attenuation coefficients of X-rays and neutrons are both a function of the X-ray photon or neutron energy and of the material (density, composition, phases...). Contrary to X-rays, neutrons are also attenuated by some light materials, such as hydrogen, carbon, boron and lithium, and penetrate many heavy materials, such as titanium and lead. Figure 2 compares the X-ray and neutron attenuation characteristics of some materials that are employed in our experiments.

Figure 2: Beam attenuation characteristics for hard X-rays and thermal neutrons, calculated by means of Beer–Lambert’s law: beam transmittance I/I0, depending on the irradiated material and sample thickness along the beam direction [3].

Network/ Experimental facilities:

For radiography experiments we use different radiation sources and experimental facilities.

In situ X-ray radiography:

  • The X-ray laboratory at the MHD department (link our lab) (conventional X-ray sourses);

In situ synchrotron radiography:

Neutron radiography:

  • The beamline NEUTRA The beamline NEUTRA of the neutron source SINQ (The Swiss Spallation Neutron Source) at the Paul Scherrer Institute in Switzerland.

A series of radiographic images are recorded in real time with an acceptable time resolution. It was successfully applied in recent years for investigations of a mass transfer and flow phenomena in liquid metals, liquid metal batteris, flowing foams and solidification processes.

Figure 3: a) Snapshots of bubble chain in the liquid GaInSn alloy [4]; b) snapshot of the dendritic structure with reconstructed melt flow using the Optical Flow approach [5]; c) a synchrotron radiograph of an indium dendrite [6]; d) a neutron radiograph of a Na-Zn liquid metal battery [7].

References:

[1] P. Russo (Ed.), Handbook of X-ray Imaging: Physics and Technology, Series in Medical Physics and Biomedical Engineering, CRC Press, Boca Raton, 2017.
[2] M. Strobl, I. Manke, N. Kardjilov, A. Hilger, M. Dawson, J. Banhart, Advances in neutron radiography and tomography, Journal of Physics D: Applied Physics 42 (2009) 243001.
[3] Lappan, T. et al. (2021). X-Ray and Neutron Radiographic Experiments on Particle-Laden Molten Metal Flows. In: Lee, J., Wagstaff, S., Anderson, A., Tesfaye, F., Lambotte, G., Allanore, A. (eds) Materials Processing Fundamentals 2021. The Minerals, Metals & Materials Series. Springer, Cham.
[4] Olga Keplinger, Natalia Shevchenko, Sven Eckert, Experimental investigations of bubble chains in a liquid metal under the influence of a horizontal magnetic field, International Journal of Multiphase Flow,Volume 121,2019,103111
[5] S. Karagadde, L. Yuan, N. Shevchenko, S. Eckert, and P. D. Lee, 3-D microstructural model of freckle formation validated using in situ experiments, Acta Mater, vol. 79, 2014.
[6] H. Neumann-Heyme et al., Coarsening evolution of dendritic sidearms: From synchrotron experiments to quantitative modeling, Acta Mater, vol. 146, 2018.
[7] Martins Sarma et al 2024, Reusable Cell Design for High-Temperature (600 °C) Liquid Metal Battery Cycling J. Electrochem. Soc. 171 040531