Speaker
Description
Runaway electrons (RE) pose significant challenges to plasma-facing components in large tokamaks due to their high energy, which can damage materials and limit plasma operations. Therefore, understanding and controlling RE is a critical area of research, particularly for devices
like ITER, where runaway events could have severe consequences. In order to address these challenges, the behaviour of RE is being studied in present-day tokamaks using advanced diagnostic tools such as the Runaway Electron Imaging and Spectroscopy System (REIS) [1]. In this work, measurements of synchrotron radiation emitted by RE in the WEST (Tungsten
Environment in Steady State Tokamak) [2] tokamak are presented. Up to 400 milliseconds RE beam have been achieved in post-disruption mode. A method based on the comparison between experimental and simulated data has been adopted to infer the RE number, pitch angle, energy and radial profile. The experimental data are synchrotron spectra collected by REIS in the range 520-4000 nm and images obtained by visible and infrared cameras. The simulations are carried out bymeans of the synthetic synchrotron radiation diagnostic tool SOFT (Synchrotron-detecting Orbit Following Toolkit) [3]. The results provide information on the dynamics of RE in pre- and post-
disruption phases in WEST discharges from recent experimental campaigns (2023-2025).
References
[1] G. Ghillardi et al., Study of runaway electron dynamics in FTU using synchrotron spectra and imaging
measurements, Plasma Physics and Controlled Fusion 67 (2025) 055029.
[2] J. Bucalossi et al., The WEST project: Testing ITER divertor high heat flux component technology in a steady state
tokamak environment, Fusion Engineering and Design, 89 (2014) 907.
[3] M. Hoppe et al., SOFT: a synthetic synchrotron diagnostic for runaway electrons, Nuclear Fusion 58 (2018) 026032.
