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Cryomodule string assembly in SM18 (II)
Present: Paul Kohler, Chiara Pasquino, Nuria Valverde
Chiara presented a planning of the vacuum components for the CERN DQW cryomodule.
It was agreed to prepare pieces in advance when there is availability from SRF colleagues.
Extremity vacuum chambers:
Gate valves and pumping cross are ready and available. Ionic pump and various gauges or angle valve are known pieces and were not discussed further in detail.
Chiara will provide a pumping cross to Paul to check it and maybe do some cleanroom measurements. If rinsing under nitrogen is needed (to avoid oxidation) then we will need a dedicated tooling.
Chiara will check on her side if coating of the pumping cross will be needed. This has an impact on the unti-dust preparation.
EN-MME developed together with SRF some dedicated tooling to stock in cleanroom for leak check or intermediate steps, and assemble the entire extremity chambers, plus mount them on the string line.
Depending on the first tests done with the pumping cross during summer, it should be re-discussed if the secondary line should not also follow the process flow of the primary line.
PIMs:
First PIM will be ready by the end of September.
Paul would like to perform a rinsing on a final assembled PIM. The assembly process pollutes the PIM components from ~ISO 3 to ~ISO 6. If we could rinse it afterwards, it would improve the quality and we could be less strict on the assembly process itself (in cleanroom).
Chiara will check if she has a prototype that Paul can use for this test.
Beam screen:
There is one ready and the series will come gradually. They will be stored under vacuum in separate chambers.
Paul would like to rinse a beam screen to check if the ~ISO 8 measurements done on the RFD beam screens can be improved and assess if an assembly in cleanroom directly as part of the cavities assembly flow can be an option (even if they have to be taken out of cleanroom for plasma cleaning and welding).
Chiara explained that TE-VSC is doing some studies to check if the screens can be cleaned after coating.
For the moment we keep the strategy as done for RFD with no rinsing.
Paul recalls usually if components can handle chemical degreasing and rinsing done by TE, Paul considers the component can handle SRF anti-dust preparations as well. More discussions to come.
For the moment it is considered that the extremity vacuum chambers and PIMs of the non-beam line (secondary line) will be assembled by TE-VSC (leak check an RGA as well). However depending on the assembly strategy, they might need to be assembled in cleanroom by SRF.
Chiara will discuss internally the involvement of TE-VSC on the leak checks and RGAs in cleanroom of all the components during string assembly. We can continue with the same strategy as for the cavities or someone from TE-VSC should be available to perform those tests in SM18.
The cleanroom team is always open if it can help TE-VSC that anti-dust preparation tests are conducted on TE-VSC thickness samples, dummy samples, or prototypes, to understand better how the thin films are behaving.
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