Polarimetric optical fibre sensing for plasma current measurement in thermonuclear fusion reactors

For plasma current sensing in next-generation Tokamak thermonuclear fusion reactors like ITER and DEMO, optical fibre-based polarimetric sensors appear to be an alternative to conventional technologies (Rogowski coils, pick-up coils) thanks to a direct measurement of the plasma current (the polarization rotation is proportional to the current) and to an expected robustness against radiations. Optical fibre sensors also offer the possibility to avoid the use of a large number of electrical cables required in conventional technologies. In this paper, we propose to summarize our last results in FOCS (Fibre-Optics Current Sensor) and POTDR (Polarization Optical Time-Domain Reflectometer) sensors based on spun and low birefringence fibres, respectively. This study will be contextualized in the frame of the future ITER fusion reactor. Experimental results obtained on the JET tokamak for the FOCS approach and the TORE SUPRA tokamak for the POTDR approach will also be presented.