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Re: 2018 Operation

Posted: Wed Apr 25, 2018 7:50 am
by DCWhitworth
Wow, thanks for the really comprehensive report with fantastic detail. I love these sorts of little detail and the amazing detective work that goes into working out what's going on.

Re: 2018 Operation

Posted: Fri Apr 27, 2018 9:42 am
by dukwon
There's a new lumi plot interface on the LPC website:
https://lpc.web.cern.ch/cgi-bin/plots.py?year=2018

Re: 2018 Operation

Posted: Mon Apr 30, 2018 12:52 pm
by neocortex
Thanks for the lumi plots. Those would be the most accurate, right? Aside from the official atlas and cms estimates after van der meer calibration.

Re: 2018 Operation

Posted: Tue May 01, 2018 11:52 pm
by jmc2000
The 2018 data-taking run at the LHC has begun:
https://home.cern/about/updates/2018/04 ... -has-begun
The LHC operators will keep ramping up the number of bunches, aiming to hit 2556 bunches in total. This will help them achieve their target of 60 inverse femtobarns (fb-1) of proton-proton collisions this year delivered to both ATLAS and CMS, 20% more than the 50 fb -1 achieved in 2017
No mention of the 16L2 problem and the current instantaneous luminosity is already at 1.7\nb/s with 1887b. I don't quite see how they can go to 2556 bunches if the max luminosity is limited to 2.0\nb/s.

Re: 2018 Operation

Posted: Wed May 02, 2018 5:02 am
by dukwon
I don't quite see how they can go to 2556 bunches if the max luminosity is limited to 2.0\nb/s.
There are more ways to control luminosity than number of colliding bunches. All IPs have routinely used levelling since last year.

Re: 2018 Operation

Posted: Wed May 02, 2018 8:10 am
by dukwon
16L2 news: a combination of a bump and controlling the corrector current have dramatically reduced the loss spikes at 16L2 for B2. They are currently doing the same for B1, but it will only be effective until halfway through the squeeze.

B2 is also behaving weirdly: a larger satellite population, debunching at injection and lower intensity of the first train.

Re: 2018 Operation

Posted: Thu May 03, 2018 2:32 am
by neocortex
Thanks for keeping us informed about 16L2. Looks like they didn't get all the crap out of the beam screen during warm-up, but just enough to make the use of orbit bumps feasible again. Up to ~2100 bunches now with no signs of slowing :) The data haul for this year is going to be insane. Hopefully a 5 sigma gets spat out.

Re: 2018 Operation

Posted: Thu May 03, 2018 10:25 am
by dukwon
The threshold of 1200 bunches, which is considered significant in terms of data taking, was expected to be reached around 11 May, but it was already reached on 28 April. A revised 2018 LHC schedule, which takes into account the faster than anticipated commissioning, has been approved and published, providing 131 days of physics with 25 ns proton beams, 17 days of special runs with protons, usually at a lower luminosity production rate, and 24 days of lead-lead collisions at the end of the year.
https://home.cern/cern-people/updates/2 ... eaning-lhc

Re: 2018 Operation

Posted: Thu May 03, 2018 10:16 pm
by dukwon
2319b fill at the moment. There is a 2460b step before 2556b beams. Looks like they're just doing 1 fill per step now. LHCb is finally getting at least 400 Hz/μb. Loss spikes around 16L2 are dramatically reduced in both beams.

Re: 2018 Operation

Posted: Sat May 05, 2018 12:11 pm
by dukwon
Stable beams with 2556b. Intensity ramp is finished. Now we're really in full swing. :clap:
lhc1.png

Re: 2018 Operation

Posted: Sun May 06, 2018 10:49 pm
by andrewp
t(SB) or the current stable beams duration is DIFFERENT on the Page 1 display and the Dashboard display (currently 10:10 hrs on Page1, 11:xx on Dashboard). Fixable? Which is correct?

Re: 2018 Operation

Posted: Sun May 06, 2018 10:57 pm
by neocortex
Page1 is currently stuck, and so are many of the other pages. Notice the timestamp. Dashboard is currently still working and displays the correct duration for stable beams. The operators will fix the other pages when they realise they're stuck. It can happen from time-to-time.

Re: 2018 Operation

Posted: Mon May 07, 2018 6:47 am
by dukwon
Screenshot from 2018-05-07 08-41-10.png
Screenshot from 2018-05-07 08-41-43.png
ATLAS and CMS lumi:
Screenshot from 2018-05-07 08-41-27.png
LHCb lumi:
IntegratedLumiLHCbTime_Yearly.png
IntegratedLumiLHCbTime_Yearly.png (28.82 KiB) Viewed 10361 times

Re: 2018 Operation

Posted: Tue May 08, 2018 9:44 am
by dukwon
LPC minutes from yesterday: https://lpc.web.cern.ch/lpc-minutes/2018-05-07.htm
  • Unclear if dumps over the weekend were due to beam intensity. Bunch intensity has been reduced as a precaution.
  • Crossing angle and β* anti-levelling as standard in each fill. The latter causes jumps in lumi at IP2 and 8, which is a bit of a problem for ALICE
  • B2 debunching (mentioned here) was found to be primarily due to a saturating klystron. Its voltage has been raised to compensate, and the abort gap cleaning has also been modified.
  • The issues near 16L2 so far have been suppressed with the solenoid and nearby correctors which were adjusted to always have a non-zero current. After the introduction of the latter, no more spikes seen though steady state losses near 16L2 are still present.

Re: 2018 Operation

Posted: Wed May 09, 2018 2:35 am
by tomey36
Thank you so much for the updates!!! You rock!!