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5th Quench Behavior Team meeting
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Europe/Zurich
Minutes of the 5th meeting of the Quench Behavior Team
Date: 2015-11-12, 10.30-12.15
Place: 927
Presents: G. De Rijk, P. Hagen, J. P. Tock, E. Todesco, D. Tommasini, B. Auchmann, A. Verweij, G. Willering, S. Le Naour, M. Modena
Differences between manufacturers [M. Modena]
In 2004, the magnet group launched a joint effort to summarize the differences in procedures between the three dipole manufacturers. A. Devred and M. Pojer went visiting each of the firm premises gathering information that has been summarized in the three EDMS reports
https://edms.cern.ch/document/501385/2
https://edms.cern.ch/document/486644/1
https://edms.cern.ch/document/486697/1
Michele presents a summary of the main findings of the time, complementing with the information of the production carried out after writing these reports. In June 2004, we were in the middle of the production with top speed of one magnet per day, and a total of ~450 manufactured collared coils, ~400 manufactured cold masses and ~100 magnets tested at SM18. Firm1 was at collared coil 150, Firm2 at 108 and Firm3 at 224.
Among the many small differences between manufacturing procedures, the presentation of Michele triggers a reflection about the following points.
- There was a non-negligible difference in the target for the azimuthal prestress in the ends between the three manufacturers. Firm3 had the lower target azimuthal prestress in coil ends.
- Firm3 used a metallic spacer
sas intermediate step during winding – Details will be clarified in the next meeting. - The three manufacturers had a different procedure to put longitudinal stress on the coil ends. In particular, to ensure that the bolts push uniformly on the whole coil,
- Firm1 was using several screws to push uniformly on each coil
- Firm2 used shims to compensate the difference in the length of the coils
- Firm3 was cutting the collared coil end spacers after layer assembly, and then shimming on poles.
Davide points out that a lack of longitudinal prestress according to the short dipole programme results does not produce loss of memory but rather endangering the magnet capability of reaching short sample.
- A difference in the resin used for impregnating the coil ends (STYCAST and/or ECOBOND), with Firm3 using ECOBOND, Firm2 STYCAST and Firm 1 both. To be clarified in the next meeting when the transition took place, and what happened after the date of the report.
Since the beginning of 3000 series production shows good performance, it is clear that none of the above differences can explain (alone) the loss of performance experienced after the 100th magnet.
Update on flattop quenches [G. Willering]
Gerard gives an update on the flattop quenches. Since the beginning of operation we had 5 quenches during flattop, all of them of 2000 series magnets, all of them of magnet that did not quench before, all of them quenching only once. The first three happened in sector 34, but 4th and 5th were in other sectors.
Gerard shows that the distribution in the sectors and along the production looks random. The 2000 series magnet suffered from high internal splice values. Indeed, since these magnets quench only once on flattop, it cannot be due to a resistance heating. A correlation to the internal splice values is not found. A correlation between cell temperature and flattop quenches is also excluded.
A working hypothesis could be that these are training quenches, i.e. that these magnets would quench, when pushed a few ampere above. And since they are on the edge of the stability, they quench at flattop. But why only the 2000 series? No answer here.
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