Comparing Methods for Computing the Electrical Superconducting Property With Microstructure of Electron Beam Welded High Purity Niobium

This article focuses on the effect of grain size on estimating the residual resistivity ratio (RRR) of electron beam welded (EBW) high purity Niobium (Nb) for the structural fabrication of radio frequency cavity as a particle accelerator. This also aims to investigate the effects of using different functional models on resistivity. EBW is done by varying the beam current to change the grain size so that its consequent impact on RRR can be evaluated. Grain size was found to be maximum for 70 mA and minimum for 50 mA beam current among the welded samples at HAZ and FZ. The grain size increases from the base metal toward the heat-affected zone and further to the fusion zone like any other fusion welding processes. Pure Nb being electrically superconductive below around 9.2 K in the absence of any magnetic field, it is invariably used as a resonant cavity for a particle accelerator in high energy physics. Two temperature dependent and two field dependent models are used for extrapolation of the RRR value estimation. Temperature dependent models performed the better-fitted residuals for every sample than the field models. The extrapolated RRR values obtained from these models are used to simulate the impact of beam current on grain size at different zones of welding.