• Vélez, A.; Glock, H. W.; Glöckner, F.; Hall, B.; Neumann, A.; Sharples, E.; Schnizer, P.; Tsakanian, A.; Knobloch, J.: The SRF Module Developments for BESSY VSR. In: Gianluigi Arduini ... [Ed.] : IPAC2017 - Proceedings, Copenhagen, Denmark JaCOW, 2017. - ISBN 978-3-95450-182-3, p. MOPVA053/1-4
    http://accelconf.web.cern.ch/AccelConf/ipac2017/papers/mopva053.pdf

Open Access Version

Abstract:
Helmholtz-Zentrum Berlin is developing BESSY VSR, a novel upgrade of the BESSY II facility to provide highly flexible pulse lengths while maintaining the average flux and brilliance of BESSY II [1]. The project goal is to simultaneously circulate both "standard" (some 10 ps long) and "short" (ps and sub-ps long) pulses offering the BESSY user community picosecond dynamics and highresolution experiments. The concept relies on the installation of high-voltage SRF cavities operating at the 3rd and 3.5th harmonics where the beating of the two frequencies provides RF buckets for long and short bunches. Since these cavities will operate in CW and with high beam current (300 mA), the cavity design represents a challenging goal when needing to avoid coupled bunch instabilities (CBI's). The installation of the VSR cryomodule must fit in one of the available 4-m long low beta straights. On this paper recent findings as well as project scope redefinitions are addressed together with the related technological and engineering techniques. The present SRF developments are shown, including the cavities, higherorder mode absorbers and the cryomodule cold-string design.