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865/1-D17 (CERN)
BWS Taskforce meeting 02.08.2023
Present: William Andreazza, Nabil El-Kassem, Raymond Veness, Michael Stephen Sullivan, Christine Vollinger, Anthony Harrison (Zoom), Benoit Salvant (Zoom), Giannis Papazoglou, Elena De La Fuente Garcia, Leonardo Sito, Federico Carra, Rama Calaga, Tom Levens, Carlo Zannini, Giovanni Rumolo
https://indico.cern.ch/event/1311626/
Ray: Schedule for YETS
William: Two WS ready. We're ready to replace the BA4 WS if needed. Week 47 removal of the BA5 BWS. Week 2 2024 BA5 installation. Week 3 2024 BA4 BWS installation. Should we also do the tank modification at Weeks 47,2,3? If the wires in BA4 don't break, we'll refurbish them at Week 47. Anthony is okay with William's plan.
Nabil: MD on the 27th of July, 4x72 bunches, 224 cycles recorded, intensity up to 2.2e11ppb, significant difference of temperature between H (6 Ferrites) and V (5 Ferrites and coupler), V temperature measurements shows a exponential drop with the increase of the intensity (thermionic emissions?) and shows less heating in general. it is difficult to say what it could be the cause. Data seems not so easy to interpret as the bunch lengths are varied because of RF instabilities. The difference between the ambient temperature in the tunnel and the temperature measurement from the probes is around 1⁰c to 1.5⁰c with no difference between H and V.
Michael: Why is the blue Temperature kind of constant but the orange one dropping towards the end?
Leonardo: The coupler has a big but overall positive impact on the impedance. The peaks are lower. With 6 Tiles there is more power dissipated on the wires than with 5 Tiles plus coupler. The dissipated energy on the 6 Ferrites is lower than what we have on the 5 Ferrites. Coupler has a big positive impact on the impedance. It must be noted that even though the maximum temperature in the tank with 5 tiles and the coupler is lower than that in the tank with 6 tiles, the average temperature with the coupler is higher than with 6 Tiles.
It would be interesting to do a simulation with 6 tiles plus the coupler and 5 tiles without coupler.
Also simulate the MD conditions in terms of bunch length and intensity. This will allow the thermal simulations.
Ray is asked if this is the best Ferrite we could use. Christine answered that this is the best available Ferrite within the ones available for vacuum. In damping properties there could be better ones. But these are not vacuum approved.
Ray: We need to urgently acquire at least 13 Ferrites.
We can find ferrites possibly with Oliver Aberle in stock. Mike Barnes may also have some - but perhaps not the good type. We can also probably acquire some ferrites from the former PS WS tank in the long-term storage, though they are a bit radioactive.
Christine: The supplier is known.
Federico Carra has multiple Ferrites with different dimensions.
The simulations are showing no difference caused by the orientation Vertical or Horizontal.
Rama: Significant power is coming out mainly from 160MHz and 800MHz modes. Additional slides shown of the spectra from couple. Data exists on power from coupler, and this has been scanned.
Ray on Microscopy results: The results from April are not quite conclusive. Both forks at the motor end and shaft end are still attached. Some of them had a piece of wire remaining (41677). The wire looks as if it melted. Perhaps caused by sublimation. On the shaft end piece, the diameter gets smaller and smaller and its surface looks like it boiled out. It seems like the shaft end melted and then the wire on the motor end just broke. However, the copper looks almost intact on the shaft end, and it looks bad on the motor side. Which opposite to what you'd expect.
Preliminary conclusion: Shaft end shows failure consistent with wire sublimation. Tapered transition to necked end. The surface damage consistent with phase transition. Motor end shows failure consistent with mechanical wire breakage. It appears that material has been deposited on the ends. We are waiting for the material type results from the metrology.
William: Which type of modification should we use for the modification of the tanks. 5 Ferrites with coupler or 6 Ferrites. Should we go to the original layout? Vertical WS in BA4 and horizontal in BA5. Ferrite tiles need time to be procured, we need more time. When will final decision be taken? Shall we change the BA4 WS wires even if they will survive the 2023 run? This way we will be able to take the wires in one piece to metrology. These questions should be answered by September. However, we shall proceed with the procurement of the Ferrites ASAP.
We should try and reach 2.21e11 ppb intensity and 1.4ns bunch length by the end of August. However, we should probably wait till everyone is back from their vacation.
Next meeting is around the 20th of August, when everyone is back from their Holidays.
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