First ideas on particle free installation of BESSY VSR Operating SRF systems reliably in a “dirty” accelerator First ideas on particle free installation of BESSY VSR Daniel Wolk BESSY II vacuum group

Vacuum system: The current design Ring section for VSR installation 15 m 15 m 30 metre section VSR module with dummy cryo tank in the middle superconducting cavities require low-particle atmosphere what are the current issues we are facing in terms of low-particle let‘s zoom in on a section VSR module dipole dipole dipole U125-2 dipole UE56-2

Vacuum system: The current design gate valve VC5 VC6 VC8 Bellow VCT2 VC10 VC5 section between the dipoles is around 4 metres long hide the magnets to see the vacuum system between the dipole chambers labeled VC5 there are 4 vacuum chambers, a bellow, a gate valve and two getter pump connectors between these 6 elements alone there are 7 CF-flange connections additionally 4 pump connectors, and 1 absorber connection ion pump connectors ~ 4 m

Vacuum system: The current design Problem 1: fragmented vacuum system, many connections Problem 2: inefficient pump nozzles Problem 3: inconvenient ion pump connectors in short: the vacuum system is fragmented some connections can be pre-assembled in a cleanroom, but not all nozzles for the pump connectors are not very efficient originally calculated with pencil and paper in the 90s, more recent simulations suggest only a few % of the pump performance connectors for the ion pumps have to be assembled through the yoke of the quadrupole

Vacuum system: redesign, improvements and installation approach re-design fewer, longer vacuum chambers  less fragmentation, fewer connections, easier pre-assembly NEG coated chambers improved ion pump nozzles with smaller ion pumps new dipole supports additional gate valves new BMPs synchrotron radiation absorbers approach re-design fewer, longer vacuum chambers  less fragmentation, fewer connections, easier pre-assembly NEG coated chambers improved ion pump nozzles with smaller ion pumps new dipole supports additional gate valves new BMPs synchrotron radiation absorbers approach installation pre-assembly in cleanroom portable clean enclosure to assemble remaining connections approach installation pre-assembly in cleanroom portable clean enclosure to assemble remaining connections

Vacuum system: improvements towards VSR operation Pressure profile - currently and with planned improvements simulation actual setup measurement actual setup simulation upgraded setup VSR module cold simulation upgraded setup VSR module warm Red: simulation of the pressure Blue: actual measurements, electrical current of the ion pumps from which the pressure can be inferred Very important for us: allows to put the simulation (red) into perspective, validates it Black and Green graphic courtesy Volker Dürr and Christian Kalus

First ideas on particle free installation of BESSY VSR Operating SRF systems reliably in a “dirty” accelerator Thank you for your attention! First ideas on particle free installation of BESSY VSR Daniel Wolk