Wunderer, N.; Dürr, V.; Frahm, A.; Glock, H.-W.; Glöckner, F.; Knobloch, J.; Sharples-Milne, E.; Tsakanian, A.; Vélez, A.; Bonezzi, M.; D'Ambros, A.; Paparella, R.; Guo, J.; Henry, J.; Rimmer, R.: VSR DEMO COLD STRING: RECENT DEVELOPMENTS AND MANUFACTURING STATUS. In: SRF 2021. , 2021
Open Accesn Version

Bunch length manipulation is mandatory in modern storage ring light sources and CW SRF provides the required high voltage in a compact system to reach this goal [1]. One possible technique as proposed in [1] is to combine higher harmonic SRF cavities (3 and 3.5 harm.) with the fundamental frequency of the BESSY II storage ring. VSR DEεO seeks to develop and demonstrate the required SRF technology to achieve this by means of “off-line” testing at Helholtz-Zentrum Berlin (HZB) Supraδab facilities of a setup comprising two 1.5 GHz SRF cavities. Due to the high level of higher order mode (HOε) power expected, caused by the beam-cavity interaction, these SRF cavities will be equipped with waveguide-connected HOε loads. On the cavity a blade tuner and piezos will be installed for frequency control and microphonics detuning. To demonstrate the feasibility of this complex system the VSR DEεO cold string consists of two cavities, each featuring five waveguides and a fundamental power coupler (FPC), plus all elements connected to the beam vacuum. For most of these components the fundamental development work is complete and has been reported in the past. This paper summarizes recent enhancements, component design detailing and the manufacturing status.