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865/1-D17 (CERN)
Meeting Notes - May 26, 2023
Attendees: Raymond Veness, William Andreazza, Benoit Salvant, Nabil El-Kassem, Christine Vollinger, Anthony Harrison, Thibaut Lefevre, Giannis Papazoglou (Zoom), Heiko, Giulia, Michael Sullivan, Jonathan Emery, Kevin Shing Bruce Li, Ivan Karpov, Carlo Zannini, Federico Carra.
- Ray: Mandate - agreed.
- Nabil: showed intensity at flat top in 2022 vs 2023 with blue lines on the graph indicating where the WS broke.
- Carlo: Wire breakage details.
- Presented the time of the second replacement wire breakage in relation to MKP-S intensity.
- High repetition rate with high-intensity beam.
- Uncertainty of approximately 2 weeks for the first breakage.
- Plotting the exact dates of the first breakage would be helpful.
- Wire breakage typically occurs 20-30 minutes after the first use of the beam, indicating that normal operation is usually not an issue. However, it can be observed during a 'long' LHC fill. The transfer function of the acquisition system 'error' results in almost twice the power at shorter bunch lengths.
- Bunch length is shorter than initially expected, around 1.5 nm (Giulia mentioned a desire to go down to 1.4 nm). Thibaut raised concerns about the low bunch length and its control, suggesting measurement and potential beam dumping. Next steps: See the sensitivity of the scanner heating to bunch length.
- Pre-measurements of beam parameters were conducted, and re-measurement with an MD is planned using 4 batches of 72 bunches at 1.35e11 bunches.
- Heiko Damerau: Reproducing wire breakage conditions.
- Bunch length is shorter than originally expected.
- Ray: Understanding operating conditions.
- Focus on bunch length and bunch intensity.
- Thibaut: Machine should be operated without hardware breakage.
- BGI and BWS were designed under similar conditions.
- Simulations for the faster scrubbing mode were not performed.
- Michael Sullivan: Update on the simulations and mitigation options.
- Simulations adjusted to reflect reality. Adjustments to wire geometry and larger gaps to the wall. Differences in fields between old and new models were significant.
- Small changes in mechanical design can significantly affect resonance frequencies.
- Consider design modifications until the next YETS if beneficial according to the Impedance group.
- % loss is % of the modes, so this is already reduced.
- Ferrite is a possible mitigation option. Simulations with ferrites showed reduced loss percentage in the modes.
- Christine
- Installation of a coupler to identify and address the modes affecting the wire.
- Mode at 770MHz is likely problematic, equally the 170 MHz mode. From the 770MHz mode, it could be identified that the model needed correction. The 170 MHz mode was observed in simulations, but not with probe measurements on-axis, only from the coupling to the wire measurements.
- 1 GHz is also bad, but hard to get rid of.
- Modes 1 and 2 with lower Q can be manipulated, but mode 3 presents challenges.
- High Q modes bad as probably see during the frequency sweep. Discussion, not necessarily the case.
- Ray: Emphasizing the importance of gathering more information from wire breakages.
- TS1 actions and recommendations:
- Prepare two spare instruments.
- Prepare ferrites for installation.
- Modify BA4 layout to convert one vertical BWS to a horizontal BWS.
- Weld ferrite using a gun from the Vacuum group on the vertical BWS. (Action: Exact position for the ferrites needs to be provided by the impedance group)
These meeting notes summarize the discussions and action items from our meeting held on May 26, 2023.
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