Present: Michal Krupa, Patric Muggli, Marlene Turner

BPM for Wire Scanner- Informal Discussion

• Cavity BPMs may achieve sub micron level resolution for a single pass measurement.
  • Not typically used at CERN (CERN design are at best 10-20 um resolution) but there should be some at CTF3 and CLEAR (provided by a collaborating institute). Devices and read out electronics should also exist for these devices.
  • Aperture depends on the frequency that you choose. On the order of 40mm is realistic.
  • PSI has a very good cavity BPM.
  • Best estimate is that on the order of ~10cm of beamline space is needed for the device --> needs to be checked
  • What does happen when the proton bunch goes through. Can the signal be handled by the electronics. Needs to be checked.
  • Ask CLEAR about operational experience, if going for a cavity BPM would need to be tested at high temperature.
•  Operation in heat and vapor
  • There is no problem of putting an entire BPM in vacuum. 
  • Resolution of BPMs is usually noise limited. Two options to improve: Make BPM smaller or repeat measurement many times.
  • BPM is electromagnetic coupler. If the field is not altered, BPM works. Presence of low density vapor should not be an issue.
  • At CERN, BPMs have been built up to 250 degrees. Materials need to be compatible with the temperature. Main problem connectors and cables.
    • Mechanical motion: when things get hot, pieces may be moving. Patric: relative measurement would be sufficient. Mode may be need to be considered when using a cavity BPM in vapor and when using in hot temperature. What would be the tolerance?

For AWAKE Run 2c: Commissioning will be done at room temperature. First such a BPM would be used in the commissioning chamber. Then, if possible, also in the final chamber.

Next step: --> Discuss the caity BPM option with Thibaut.