This project investigates the development of an indirect measurement technique to determine the temperature and mechanical deformation of a tungsten disc exposed to plasma conditions in the MAGNUM-PSI facility. Tungsten is a key material for diverter components in nuclear fusion reactors due to its high melting point and favourable thermal properties; however, extreme thermal and mechanical loads during plasma exposure can lead to deformation and material degradation. Accurate, non-intrusive diagnostics are therefore essential to understand tungsten behaviour under fusion-relevant conditions.
Project description
Because direct measurements are challenging in the harsh plasma environment, this study explores the feasibility of using electrical measurements as an alternative approach. Temperature determination is investigated through direct current (DC) resistance measurements, exploiting the known temperature dependence of tungsten’s electrical resistance. Mechanical deformation is examined indirectly using alternating current (AC) measurements, focusing on frequency-dependent current distribution and the skin effect.
The research combines literature review, numerical modelling, and experimental prototyping. COMSOL Multiphysics simulations were used to model the tungsten disc and analyse both DC resistance changes with temperature and AC current distribution at different frequencies. A DC measurement prototype based on a Wheatstone bridge was designed, simulated in LTspice, and realized on a printed circuit board. Initial laboratory tests demonstrate that milliohm-level resistance changes are detectable, although electrical noise and thermal drift currently limit measurement resolution.
Project results
The objective of this project was to investigate whether the temperature and mechanical deformation of a tungsten disc exposed to plasma can be determined indirectly using electrical measurement techniques. Based on the results of simulations, circuit design, and preliminary experimental testing, it can be concluded that this approach is technically feasible and physically well-founded.
The DC analysis demonstrated a clear and predictable increase in electrical resistance with temperature, consistent with the known material properties of tungsten. Both COMSOL simulations and LTspice circuit simulations confirm that DC resistance measurements can be used to conclude temperature changes quantitatively. The realized
Wheatstone bridge prototype is capable of detecting the small resistance variations expected during heating, validating the chosen measurement principle.
The AC analysis showed that the current distribution in the tungsten disc is strongly frequency-dependent due to the skin effect. At higher frequencies, current concentrates near the surface of the disc, making the electrical response sensitive to changes in geometry and, potentially, mechanical deformation. These results indicate that AC measurements provide a promising method for detecting deformation-related effects in tungsten components.
Although full verification under high-temperature and plasma conditions has not yet been completed, the current results demonstrate that the developed methods and prototype form a solid basis for future validation. Challenges such as electrical noise, thermal drift, and operation under realistic experimental conditions remain and must be addressed in follow-up work. Nevertheless, this project successfully shows that non-intrusive electrical measurements offer a viable pathway for monitoring temperature and deformation of tungsten in fusion-relevant environments.
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Acknowledgements
The student team (Bas and Ymke) wishes to thank Fontys Technology, Fontys Minor BeCreative, the Fontys lectorate Distributed Sensor Systems (DSS) and the DIFFER research institute at the TU/e campus for enabling and supporting this interesting project experience. Special thanks to Chris Lee (DSS) and Johan van Rens (Minor BeCreative).