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Linac4 Spare RFQ - Preparation for IEFC
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Europe/Zurich
Linac4 Spare RFQ
Present: Agathe Fleury, M. Albert, G. Bellodi, F. Gerigk, S. Ramberger, R. Scrivens, R. Wegner
Note: The presentations on this indco page are draft version for discussion, they cannot be used as definitive information.
Richard outlined the reason for the meeting.
The Spare RFQ (RFQ2) could be exchanged in LS3 wit the operational RFQ (RFQ1). This should be a short point to be included in the SY-RF presentation at the LS3 Readiness Review, and in advance the IEFC has requested a presentation next week with more details.
Exchanging the RFQs would have benefits for alignment, and give a common RF window across the RF cavities.
BE-GM noted that although the RFQ1 is very difficult to align, they can maintain the RFQ/Linac alignment until LS4 at the least.
ABP asked that the exchanged RFQ2 be tested with beam (including conditioning) in the tunnel.
Sarah reported on the impact this would have in the planning.
Taking an exchange of the RFQ at the beginning of LS3 (in parallel with some maintenance), and a test period, still allows sufficient time to complete all the other Linac4 works.
In order to maintain the services, all groups that responded could provide the services for the tests (with the controls group still to confirm).
Hence there are no show stoppers seen for such a test.
It was questioned that if tests were not successful, it may be necessary to switch back to RFQ1 (which would have to be in the original configuration to be safe) or foresee another testing period for RFQ2 if some modifications were made. In response to Markus' question, the length of time needed should be considered to be the same as the RFQ1->RFQ2 exchange. It was concluded this is not needed on the planning, just kept in mind.
The risks of exchange were discussed. At the test stand the RFQ can be tested with only shorter pulses, and the low sparking rate of RFQ1 may take some time to achieve with RFQ2 (more than allocated here). Moving the RFQs is a delicate operation that could change the RFQ performance.
It was noted that the new RFQ2 might have better performance in terms of transmission, but this is only likely to be interesting and measurable if it is of the order of 10%.
It was also noted that the RFQ1 performance is good, and now very stable with no signs of degradation.
Rolf asked what would be the plan for RFQ1 if it is exchanged, it will be converted to use the same window as RFQ2 and be tested at the test stand to make it a full valid spare for Linac4. It would also then be available for testing.
In conclusion, currently no significant arguments are there for making the exchange in LS3. Therefore we decide to alter the baseline that the RFQs will NOT be exchanged in LS3.
Nevertheless, given that no impact was seen so far on keep a test period in LS3, EN-ACE will keep this period blocked in the LS3 planning. If there comes a show-stopper for maintaining this period blocked in the planning, the status of the RFQ can be reviewed and a further decision taken.
Unless another decision date is needed, we concluded that in September 2025 the situation can be revisited (with data on the RFQ2 testing, and present RFQ1 performance) and any change to the baseline made.
Richard will also note this conclusion to BE-GM, in case this does not fit with their understanding.
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