Vacuum experiences on XFEL Beam Position Quadrupole Units (BQU) preparation Marco Schalwat TTC Topical Workshop on SRF Cryomodule Clean Room Assembly CEA Saclay, 12th november 2014

Marco Schalwat | TTC topical meeting on clean room assembly | | Seite 2 > Overview > Investigations on Vacuum pressure during storage and transportation > Investigations to solve the problem > Conclusion Outline

Marco Schalwat | TTC topical meeting on clean room assembly | | Seite 3 Overview > Since February 2012 Quadrupole Units are completed at DESY cleanroom under ISO 4 conditions > After assembly a direct shipment is foreseen (Just in time delivery) > During the ramp up phase about 6 units have been stored permanently in DESY cleanroom Storage place for BQU inside cleanroom > After the first delivery a problem with the vacuum pressure was observed during incoming inspection at CEA Saclay  During storage at DESY the vacuum pressure increases and the pressure was out of expected range

Marco Schalwat | TTC topical meeting on clean room assembly | | Seite 4 Difference on vacuum pressure Overview pressure after assembly at DESY and incoming inspection at CEA Saclay Threshold value for vacuum pressure

Marco Schalwat | TTC topical meeting on clean room assembly | | Seite 5 Investigations to solve the problem actiontimeresult check vacuum via cold cathode gauge after completion, with connection to the vacuum pump station marginal decreasing check vacuum via activated cold cathode gauge after completion, without connection to the vacuum pump station marginal decreasing check vacuum via cold cathode gauge during complete unit is disconnected from the vacuum pump station (gauge was not switched on during assembly)check was done 4 times to different units decreasing from e- 8 to e-4 mbar vacuum test on single componentsafter 50 dayspressure decreases check vacuum via cold cathode gaugedaily / check 5 hours / duration 10 dayspressure decreases check vacuum via cold cathode gaugeduration 10 dayspressure stable

Marco Schalwat | TTC topical meeting on clean room assembly | | Seite 6 Conclusion > Up to now 27 Beam Position Monitor Quadrupol Units (BQU) for the XFEL project have been send to CEA > All units have shown a degradation of vacuum by 5-6 orders of the magnitude (from to mbar) > Origin of the pressure degradation is gas desorption of all components. > Acceptance criteria for incoming inspections were changed. > After about 60 days vacuum pressure stabilized to mbar from a leak tight measured BQU > 12 BQU are assembled to modules and have been tested at DESY successfully  Pressure increased to the 10-2 mbar region does no seem to lead to problems at the BQU  Pressure increasing to the mbar does not lead to problems for the accelerator module performance ?

Marco Schalwat | TTC topical meeting on clean room assembly | | Seite 7 Thank you ! Thanks to all colleagues for their support.