Busbar arcs at large fusion magnets: Conductor to feeder tube arcing model experiments with the LONGARC device

•The LONGARC device was successfully implemented for busbar to feeder tubes arcing model experiments.•Arcing at an ITER busbar inside its feeder tube was simulated in scaled model experiments.•The narrower half tubes imply a slight increase of the arc propagation speed in compare to full tube experiments.•All simulated half tubes experiments show severe damage indicating that the ITER inner feeder tube will not withstand a busbar arc.

Electric arcs moving along the power cables (the so-called busbars) of the toroidal field (TF) coils of ITER may reach and penetrate the cryostat wall. Model experiments with the new LONGARC device continue the VACARC (VACuum ARC) experiments that were initiated to investigate the propagation and destruction mechanisms of busbar arcs in small scale [1]. The experiments are intended to support the development and validation of a numerical model. LONGARC overcomes the space limitations inside VACARC and allows also for advanced 1:3 (vs. ITER full scale) model setups. The LONGARC device and first results are presented below.