Glock, H.-W.; Dürr, V.; Glöckner, F.; Knobloch, J.; Tannert, M.; Vélez, A.; Wolk, D.; Wunderer, N.; Guo, J.; Wang, H.; Rimmer, R.: Progress of the BESSY VSR Cold String Development and Testing. In: Mark Boland ... [Ed.] : IPAC 2019, Proceedings of the 10th International Particle Accelerator Conference: Melbourne, Australia, 19-24 May 2019. Geneva, Switzerland: JACoW Publishing, 2019. - ISBN 978-3-95450-208-0, p. TUPGW019/1434-1436
Open Accesn Version

The so-called VSR (Variable Storage Ring) upgrade of the 3rd gen. light source BESSY II will provide the capability to simultaneously store long (about 20 ps rms length) and short (1 ps or less) bunches in the ring. This will be accomplished by inserting a module with four superconducting cavities, two of them operating at 1.5 GHz as the third harmonic of the 500 MHz driving RF, two at 1.75 GHz. The “cold” string of those four cavities also includes supporting and connecting devices, as there will be: - three intermediate bellows, all shielded against leaking fundamental mode cavity fields, one additionally acting as a collimator for incident synchrotron light; - two tuneable bellows at the module ends; - two warm end groups outside the module, housing toroidal dielectric wake field absorbers, another bellow and a vacuum pump connection. The recent design progress of those components will be reported, including a description of a beam test planned for the central collimating shielded bellow.