Present: A. Butterworth, I. Karpov, O. Brunner, W. Hofle, K. Canderan, L. Valle, F. Peauger, J. Heron

Discussion

Cryogenic safety and access to RF zones

• Sectorization of the RF zones is not a hard separation, rather a way of calculating air flow.

• Proposal that the smoke extraction system be used for helium

  • A problem is the sensor to extraction delay which is about 30 seconds.

• Will need to empty all cryomodules in the walking path to module which needs to be accessed.

• Trying to design around the worst case scenario:

  • New experiments and studies needed, as the worst case scenario is realistically an overestimate. Accident/consequences to be refined.

• Can avoid cavity quench loss of He in FCC as they do at ESS. Unlike LHC, where the release valves open on overpressure. To be checked in LHC.

• Circumventing access problems with remote manipulation:

  • Robots for inspection but also for interventions.
  • Specific RF robot, or the same one as in the arcs
  • Different robots for collider and booster, as the CMs are either on the ceiling or the floor.
  • We should try to sketch interventions which are possible for robots. Space constraints are different in different places.
  • Fault categorization: classify into remote repairable, repairable from klystron gallery, common mode faults, child faults, electrical glitches etc. Can then decide if a robot is worth it, looking at the likelihood of faults.

Transverse damper

• TFB is combined with depolarizer. Makes it more complicated for degraded mode.
• IPAC paper in 2024 was a snapshot at the time, number of kickers  (24) more or less defined, 25ns spacing and bunch pattern defined.
• Potential physics bunch spacing of 5ns for e-cloud, would need change of bandwidth.
• Optics choice.
• There is enough redundancy with 24 kickers for TFB operation but maybe not for depolarization.
• System distributed over 4 locations per ring, gives redundancy against electrical loss etc.
• Loss of synchronization with frev could be a common mode failure. If distributed over White Rabbit what is the redundancy?
• Instability damping is only needed at the Z working point. For W it is still needed for HOM instability. We can remove it for reliability considerations at the H and ttbar working points.
• TFB in the booster: what is needed for polarized bunches? More complex than in the collider.
• Possibly required to do active depolarization of physics bunches in the collider.
• E-POL group meeting: https://indico.cern.ch/event/1610901/