Demonstration of curved magnetically guided liquid metal target using liquid Gallium for fusion neutron sources

Abstract

A high-speed liquid lithium (Li) jet with a free surface is being developed as a beam target for Fusion Neutron Sources. Li flows vertically along a concave flow channel with a free surface exposed to ion beam and its internal pressure increases due to centrifugal force, creating a temperature margin up to the boiling point. We proposed a practical concept of magnetically guided liquid metal target (MGLT) with a curved shape for IFMIF, and our MGLT produces curved magnetic field in combination of a couple of radiation-proof resistive coils, yokes, ducts/nozzles, and high flux test module. For the demonstration of the curved MGLT, gallium (Ga) was used as working liquid metal alternative to Li, because Ga has low chemical reactivity and a low melting point. In this study, firstly, we optimized the shape and conditions of the MGLT system for the curved Ga jet through brief two-dimensional calculations of the magnetic field and the Ga flow line. Next, the experimental apparatus was constructed, and measurements of the magnetic field was conducted. Then, the Ga jet was observed using high speed video camera, and the deviation between the Ga flow line and the magnetic field line was evaluated from image analysis. The deviation in the experiment was larger than that in the calculation. This was attributed to the fact that the three dimensional effects, including the deformation of the cross-sectional shape of the Ga jet, cannot be simulated in this calculation. However, from the results, it was demonstrated that our MGLT system had the potential to curve the liquid metal jet. On the other hand, the deviation in the experiment could not be made as small as calculated, but it was possible to identify the challenges for practical application of the MGLT system.