Vélez, A.; Goslawski, P.; Jankowiak, A.; Knobloch, J.; Neumann, A.; Ries, M.; Glock, H.-W.; Wüstefeld, G.: BESSY VSR: A Novel Application of SRF for Synchrotron Light Sources. In: SRF2015 - Proceedings, Whistler, BC, Canada. , 2015. - ISBN 978-3-95450-178-6, p. TUAA03/1-5
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CW SRF Cavities have been used very successfully in the past in synchrotron light sources to provide high power acceleration. Here we present a novel application of higher harmonic systems of two different frequencies (1.5 GHz and 1.75 GHz) to generate a beating of accelerating voltage. With such a system it is possible to store "standard" (some 10 ps long) and "short" (ps and sub-ps long) pulses simultaneously in the storage ring. This opens up new possibilities for light source users to perform picosecond dynamic and high-resolution experiments at the same facility. The demands on the SRF system and RF control are substantial and a new design, based on waveguide damping, is currently being developed. This system will be used for a major upgrade of the BESSY II facility to the BESSY Variable Pulse length Storage Ring (BESSY VSR) for a next-generation storage-ring light source. We will discuss the concept, challenges and designs for BESSY VSR from the SRF point of view.