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Precursors to flattop quench in CP and Q3
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Europe/Zurich
Dear all,
First thanks for your participation this morning.
A quick summary of our meeting:
- Jordan showed all relevant active controls, regulations and measurements. The temperature and pressure variations cannot be traced back to issues with the cryogenic control system, and with the existing data we can conclude that the cryo control system is functioning correctly. There were no new conclusions or discoveries compared to the earlier discussed data a few weeks ago. We all agreed that the synchronization of the data is good and that there is in fact a precursor/transient happening before the quenches and that it is therefore very unlikely that the magnet itself produces the quench.
- Torsten explained how the slow process of condensation of helium particles on 1.9 K surfaces could lead to a more sudden/transient event where the helium particles are released and provoke the precursor as discussed. At a vacuum pressure of 5*10-5 with an existing leak of helium gas into the vacuum, this could be a likely explanation. This would be good news, since with the leak repaired the following magnets should not suffer from the same events.
- No further detailed calculations of how enough heat can leak to the magnet were performed. There are a large set of unknown parameters, which makes it a complex calculation.
- Action points: The next CP is planned for testing mid-august.
- Additional measurements (need to be ready by end of July for preparation):
- Additional temperature measurement in the vacuum on the MRB side (similar to TT151).
- Verification if a PT100 temperature probe can be placed on the anti-cryoststat
- Additional pressure sensor for the vacuum (use the entry port of the second vacuum pump system).
- changes in measurement of actual sensors:
- Increase sampling and database storage frequency of the main temperature and pressure probes to 10 Hz if possible (TT151, PT181, TT821, TT106, etc.)
- Ensure anticryostat data (heating power and temperatures) are stored with 10 Hz.
With a bit of luck, the helium leak was the source of the problem, but if not, it is important we have all data available to investigate in more detail.
Please let me know if I need to correct something, or if there is something to be added. I will also attach this summary to the indico page.
Best regards,
Gerard
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