1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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