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WP11 meeting
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Europe/Zurich
Present: A Lombardi, R Scrivens, A Grudiev, H Pommerenke, G Bellodi
AL summarised the list of parameters of the baseline RFQ3 beam dynamics design, for hand-over to the RF group for RF design. These are essentially:
R0=0.33cm, rho=0.28cm, L=352cm, V=85kV.
The simulated modulation profile is sinusoidal, though this is not completely fixed yet.
AG asks to have more detailed information on the cells, in order to identify the most critical one and make sure the max Efield is not exceeded. They would also like to have information on how the Efield varies along the vanes.
AL will provide the surface field profile along the vanes and more detailed modulation info, sharing files on th Indico page of the meeting.
Next step for ABP is to create a field map file of the baseline RFQ3 solution described, to be integrated in PATH simulations for detailed studies of losses distribution and final confirmation of the beam dynamics design.
It is proposed to converge on a baseline design to be presented at the March 2022 internal review and continue the studies to explore solutions quite radically different (for example employing two RFQs with a chopper in between) and check possible advantages of these out of the scope of a more 'standard' design.
aiming at 100% transmission would give very long length probably (IPHI example) - what is achievable?
Doubting that the observed Linac4 RFQ blistering could be detrimental in the long term, AG asks if we should not aim at having a design with 100% transmission. AL replies that this would most probably entail having very long structures (e.g. 6m long IPHI example).
RS replies that stripping induced losses at the RFQ entrance are in any case unavoidable, thus setting already a non-zero lower limit for losses. A few per cent losses in the paper design are thus deemed acceptable.
AG also asks about the duty factor assumed, since this would influence the design of the cooling channels.
RS replies that at the moment there is no stated interest from the LHC towards a higher rep rate. He will enquire with the Physics Beyond Colliders group to see if there are any specific requests in that direction.
The next meeting is scheduled for Thursday November 25th, with a first presentation on the RF design.
Minutes by GB, 04/11/2021
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