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All sectors cold, powering tests ongoing. After cavern closure (24th March) Sector 23 needs a new magnet training campaign: ~20 quenches, 2 weeks estimated, then ready for beam injection.

A nice demonstration of gas-filled particle detectors fulfilling a secondary/unintended function as barometers

https://alice-collaboration.web.cern.ch/node/35254

Here's my cartoon guess of what happened: Essentially, the finger must have buckled somewhat at low temperature, then at the warm-up in Feb 2019, it was bent even further by the gap closing due to thermal expansion.

Here's a description of RF fingers from the ESRF website To absorb chamber-to-chamber misalignment and thermal expansion, [...], bellows are used to inter-connect a large number of chambers along the ring circumference. These bellows, however, are seen as resonant cavities by the beam hence breaking...

Since we're (slowly) discussing YETS, I've added it to the topic. I suggest making a new thread "2022 operations" in March

Here is the aforementioned buckled RF finger found in 21L3

Beam test summary in these slides from Evian: https://indico.cern.ch/event/1077835/co ... s/4533367/

In November there was the "Evian" Workshop (actually held at CERN due to COVID)
Slides available here: https://indico.cern.ch/event/1077835/timetable/
For the impatient, I recommend checking out the summary talk at the end.

The "ULO" has been identified as a buckled RF finger, so sector 23 will be warmed up for an intervention. This delays the restart by several weeks. (However, better to catch it now than then!)

Highlights from the beam tests:

• High machine availability throughout the tests (~90%)
• 40 hours of stable beams over 5 nights (6 hours planned)
• All key instruments working, mostly from day 1
• ULO found at 21L3
• Opportunistic ramp to 3.5 TeV with pilot beams

Aperture scans found a "unidentified lying object" (ULO) at 21L3. A bump of a few mm is sufficient to clear it with no problem.
This mirrors the 2015 post-LS1 commissioning, where a ULO was found at 15R8, which turned out to be a piece of plastic

Now stable beams!

Welcome. I did see you pop in to the IRC channel the other day. Be aware that it moves fairly slowly (at the moment dominated by LHC comments) but there are a few human users who pay attention. I recommend using a bouncer or something like IRCCloud to stay connected.

First colliding single bunches at 450 GeV in 'adjust' at all IPs! First stable beams scheduled for tomorrow

B1 was struggling a bit with high losses, but now it has made an appreciable number of turns (small blue blip!)

One probe in B2 now circulating stably