An alternative scheme for stiffening SRF cavities by plasma spraying

Stiffening of bulk niobium SRF cavities is mandatory for reducing the frequency shift induced by Lorentz forces at high accelerating gradients. Experimental and computational data previously reported show that with the actual scheme (i.e. EB welded stiffening rings) the frequency shift of TESLA 9 cells SRF cavities is higher than the cavity bandwidth above Eacc=28 MV/m. We propose a new stiffening method, using a Plasma Sprayed Copper Layer (PSCL) onto bulk niobium cavities. As compared to the actual technique, this method offers several advantages (simplicity, reliability...). The first experimental data obtained with monocell cavities produced by this method demonstrate the efficiency of cavities stiffening with plasma spraying. Thermal and mechanical properties measured on niobium samples with a PSCL are also presented. These data will allow us choose the plasma spraying process suitable for achieving the best cavities performances.