Search found 168 matches

by mfb
Mon Jul 18, 2016 5:35 am
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 29697

Re: 2016 operation

They re-optimize the beam parameters frequently. This is partially necessary due to the ... moon.

Seriously


First BCMS beams: A new luminosity record at 110% the design luminosity, achieved two out of two times so far.
by mfb
Sat Jul 16, 2016 11:31 am
Forum: The Accelerator
Topic: What are the current records for LHC fills?
Replies: 45
Views: 29485

Re: What are the current records for LHC fills?

The new BCMS ("Batch Compression, Merging and Splitting") works, the first run using it for a lower emittance directly reached 110% design luminosity, a new record but probably not the last one. More details on how it works (2012) . The basic idea: reduce bunch splitting in the PS to keep a lower em...
by mfb
Thu Jul 14, 2016 3:48 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 29697

Re: 2016 operation

Interesting news from the LPC meeting , first set of slides, in particular slide 14. Going from 96 to 144 bunches per injection can give up to 15% (ATLAS/CMS) or 20% (ALICE/LHCb) more bunch crossings - free luminosity increase without increasing pileup notably. Heat load would be worse but could be ...
by mfb
Mon Jul 11, 2016 8:25 pm
Forum: The Accelerator
Topic: What are the current records for LHC fills?
Replies: 45
Views: 29485

Re: What are the current records for LHC fills?

3.1/fb in a week (Monday->Monday) is a new record. 80% time in stable beams. 12 weeks of physics left this year. I don't expect all of them to be that good, but we are well on track for more than 30/fb. Looks like the SPS beam dump won't get fixed this year, but going to 144 bunches per injection (i...
by mfb
Sun Jul 10, 2016 6:23 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 29697

Re: 2016 operation

There's an interesting paper on BCMS mentioned in the link which is now being used for fills as we speak to increase the luminosity further: http://emetral.web.cern.ch/emetral/SomeOtherInterestingTalksAndPapers/BCMS@LMC_EM_18-02-14.pdf Note that the link is from early 2015. The current SPS limit wo...
by mfb
Thu Jul 07, 2016 7:26 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 29697

Re: 2016 operation

The luminosity lifetime might go down a bit, but for a given time in stable beams the luminosity should always be higher, so no disadvantages (higher pileup in the experiments, but that's what you get if you want more luminosity for a given number of bunch crossings). Just challenging for the preacc...
by mfb
Thu Jul 07, 2016 5:54 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 29697

Re: 2016 operation

They plan to reduce the emittance a bit, which could increase the luminosity further even without a fix of the SPS issue.
by mfb
Wed Jul 06, 2016 9:17 pm
Forum: The Accelerator
Topic: What are the current records for LHC fills?
Replies: 45
Views: 29485

Re: What are the current records for LHC fills?

Didn't hear anything new about the SPS beam dump for a while. I guess a replacement is in production, but it is unclear if it will be installed this year. Currently they can't get more bunches in simply because the LHC ring is full. See the end of the previous page and the start of this post for an ...
by mfb
Tue Jul 05, 2016 11:20 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 29697

Re: 2016 operation

I added the recent progress and extrapolated a bit, including the technical stop and the large beta* days, but not the weasel incident or the POPS PS issue. MD and TS can reduce that a bit, as can a worse machine performance. On the other hand, a fixed SPS beam dump vacuum could increase the luminos...
by mfb
Tue Jul 05, 2016 8:15 pm
Forum: The Accelerator
Topic: What are the current records for LHC fills?
Replies: 45
Views: 29485

Re: What are the current records for LHC fills?

They now plan to dump the current fill in about an hour, at ~40% design luminosity after 24 hours in stable beams. The second planned dump in the last days, at a similar time. Looks like they go for 24 hours now. CMS has some weird feature in OP VISTARS where they split up the luminosity data in mul...
by mfb
Sun Jul 03, 2016 1:52 pm
Forum: The Accelerator
Topic: What are the current records for LHC fills?
Replies: 45
Views: 29485

Re: What are the current records for LHC fills?

2 Build a curve fit for atlas and CMS delivered Data vs Time Atlas y = 5.067x + 28313 CMS y = 5.2158x + 35638 Chart 1 That would suggest a constant luminosity plus some magic lumi offset - clearly not a realistic model. Something your method is missing is the correlation between initial luminosity ...
by mfb
Sat Jul 02, 2016 2:42 pm
Forum: The Accelerator
Topic: What are the current records for LHC fills?
Replies: 45
Views: 29485

Re: What are the current records for LHC fills?

You cannot really "use" faults. They can happen, and ruin your fill. Maks keeping the beam a bit better, of course, if they occur frequently. They managed to get another luminosity record this morning, ~110% design lumi for ATLAS and more than 100% for CMS. The following run was worse again - but th...
by mfb
Fri Jul 01, 2016 11:15 am
Forum: The Accelerator
Topic: Interesting dump cause today
Replies: 1
Views: 1836

Re: Interesting dump cause today

They run tests with the system now, with low-intensity beams.

The event happened 8:24, 6 minutes before today's morning meeting started, so it didn't make it into the slides.
by mfb
Thu Jun 30, 2016 5:45 pm
Forum: The Accelerator
Topic: 30,000 AMPS, WOW!
Replies: 11
Views: 6042

Re: 30,000 AMPS, WOW!

I think you mixed the CMS solenoid magnet current with the LHC dipole magnet inductance, the dipoles have ~10 kA current.

The 2008 dipole quench incident was caused by the energy stored in the superconducting dipole magnets. In total over the ring about 11 GJ at 7 TeV, ~15% less at 6.5 TeV.
by mfb
Tue Jun 28, 2016 2:35 pm
Forum: The Accelerator
Topic: What are the current records for LHC fills?
Replies: 45
Views: 29485

Re: What are the current records for LHC fills?

~35 hours luminosity lifetime (approximated from last fill) and 4 hours turnaround time would suggest an ideal fill length of just ~16 hours, for 0.65 times the maximal luminosity as average over the whole cycle. With 7 hours of turnaround time ~20 hours of fill time are optimal (57%), and we need 1...