Choose timezone
Your profile timezone:
Meeting to Discuss PC06 Cold Test Results and Future Plans
→
Europe/Zurich
Zoom (CERN)
Zoom
CERN
Meeting Summary:
Presentations:
Shahnam and Guillaume each presented their respective slides.
From Shahnam’s Presentation:
- PC06 exhibits a similar Q-drop behavior as PC04.
- PC04 is currently on the optical bench and will subsequently be sent to Building 107 for coating thickness measurement.
- The same procedure is planned for PC06.
- The current SM18 testing plan through the end of the year was presented showing only one slot for FCC 400 MHz R&D in December.
From Guillaume’s Presentation: Two potential causes were presented for the observed layer peel-off:
- Surface contamination with stains, oxidation spots, and residues suggests insufficient surface control
- Coated layer might be thinner than expected
To investigate this issue, the thickness of the Nb coating on cavities PC04 and PC06 must be measured. The coating thickness is typically around 2 μm. Increasing the thickness would incur additional cost and processing time and is therefore only considered if thin or weak spots are detected.
Cavities available for FCC-related research:
- PC04
- PC06 (with wall thickness concerns)
- Two bulk-machined 1-cell 400 MHz cavities
- One of these is expected to be ready this summer.
- The second to be clarified.
Wall Thickness Concerns (PC06): The wall thickness of PC06 is in a critical range, especially near the iris region. As a result, regular wall thickness checks are required after each Nb stripping step to ensure we stay above the minimum limit. The measurements are done using the Magna-Mike system (see for example: Magna-Mike 8600), which uses a magnetic probe and a bead in contact with the cavity surface. This method may leave minor surface traces (<100 nm), which can be polished off in the next steps.
The minimum safe wall thickness is approximately 2.2 mm (to be confirmed). If the wall thickness falls below this limit, the cavity should be discarded from FCC R&D, reducing the number of usable cavities. Alexandre Porret is typically the contact person for such thickness measurements.
Regarding NC04 (LHC spare cavity): NC04 may follow a different surface preparation route using the SUBU polishing method to avoid the issues encountered with PC04 and PC06. This diverges from the FCC R&D strategy.
Open Questions and Action Items:
- Clarify who is responsible for the production and follow-up (material specification, etc.) of the bulk-machined 1-cell 400 MHz cavities.
- Determine when the two bulk-machined cavities will become available.
- Perform the wall thickness measurement of PC06.
- At SM18, only test stands V3 and V6 are suitable for LHC-size cavity tests.
- Coordination with Crab cavity measurements is necessary to ensure access to V3 (if needed).
- Guillaume should be informed of the earliest available time slot at SM18 so that he can assess whether PC04 can be prepared in time for the next cold test.
There are minutes attached to this event.
Show them.
