Craievich, P. Bopp, M. Braun, H.-H. Citterio, A. Fitze, H. Garvey, T. Kleeb, T. Löhl, F. Marcellini, F. Pedrozzi, M. Raguin, J.-Y. Rivkin, L. Rolli, K. Zennaro, R. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-194-6 10.18429/JACoW-LINAC2018-THPO115 English 937-940 THPO115 FEL linac accelerating-gradient cavity polarization Contribution to a conference proceedings 2019 2019-01 https://doi.org/10.18429/JACoW-LINAC2018-THPO115 http://jacow.org/linac2018/papers/thpo115.pdf For SwissFEL a novel production process for high-gradient, high-precision C-band accelerating structures had been developed at PSI and was implemented for series production in collaboration with industry. The copper parts of the structures are machined and brazed relying on a ultra-high precision manufacturing process and tight mechanical tolerances; no RF tuning methods are applied during or after production. So far none of the structures of the series production failed during RF power conditioning and operation in the SwissFEL facility. After completing the series production for SwissFEL PSI started collaborations with CERN, ELETTRA and DESY for applying the production process and related know-how to other frequencies, namely S-band (3 GHz) and X-band (12 GHz). This paper gives an overview on the ongoing and planned R\&D activities and results obtained so far.