Study of Superconducting RF 3 GHz Cavities Realized by Spinning

In the context of an R&D program aiming at developing new fabrication techniques, three bulk Niobium 3 GHz seamless SRF cavities were produced by spinning at INFN Legnaro. These prototype cavities for different nominal thicknesses were tested at IPN Orsay in the temperature range 1.7–4.2 K. In the course of the experiments, several parameters were investigated: surface resistance Rs vs. temperature T, magnetic penetration depth as function of T and Lorentz forces detuning factor K. Electromagnetic simulations were also performed. The results obtained are reported and discussed. The characteristics Q0 vs. Eacc of the three cavities showed field emission and the RF tests were limited by the power available. Moreover, the energy gap was deduced from the Rs vs. T results and compared to data previously reported on niobium leading to a good agreement. Finally, these cavities seem to be more sensitive (i.e. higher detuning factor) to Lorentz forces detuning compared to cavities of same geometry produced by deep drawing and electron beam welding.