Our researchers are conducting neutron radiography experiments in Switzerland

Researcher Mihails Birjukovs from the Institute of Numerical Modelling is currently working as a guest researcher in the Paul Scherrer Institute (PSI) in Switzerland. He arrived on the 5th of August and for the following two months will be conducting a three experiment series as a part of a larger research project Developing new numerical modelling tools for researching multiphysical processes in electromagnetic liquid metal technologies (Nr. 1.1.1.1/18/A/108).

In the presence of a magnetic field, the flow of bubble circuits in liquid metal is being investigated. Neutron radiography is used to monitor the flow of argon bubbles in otherwise opaque gallium. The way neutron radiography works could be compared to X-Ray radiography. Unlike X-Ray radiography that interacts with electrons, neutrons interact with atomic nuclei instead. This characteristic means that neutron radiography can be used to “see” less absorbent bubbles in liquid gallium than X-Ray radiography would allow.

Due to a significant difference between neutron absorption coefficients of argon and gallium, an image can be formed when the neutron beam interacts with the sample. In the image, the gas bubble flow can be seen. This neutron beam characteristic is being used by our researchers in order to look closer at a miniaturized model of liquid gallium that is stirred via argon gas bubble flow. The conclusions from this work can be transferred and used in larger-scale technologies as the chosen parameters for the model system are consistent with those of larger industrial systems.

Experiments are done both in the presence of a magnetic field and without it, also different gas flow velocities are used. The goal of these experiment series is to understand the influence of magnetic field orientation and intensity on gas bubble flow stability and characteristics. It is important to note that the neutron radiography technology in PSI is unique because it provides a neutron flow intensity large enough for the acquisition of high-quality images but at the same time it also allows large duration experiments that would normally not be possible because of gallium activation. Besides the experimental work, a tool for image processing is also currently being developed and improved, the use of which lets the researchers compare the experimental data with a numerical model.

An important part of the experiments was also done by Jevgēnijs Teličko who developed the liquid gallium heating and gas supply systems, by Pēteris Zvejnieks who conducted a part of the experimental series in PSI and by the leading researcher Imants Bucenieks (Institute of Physics) who constructed the magnetic field control systems used in the experiments.

This research proposal from the Institute of Numerical Modelling was announced to be the best among all the others in the call for proposals. In the near future the experiments in PSI will be continued by Mārtiņš Klevs.