The Large Hadron Collider is now ready for its next step up to 248 bunches which should raise the peak luminosity to 85/μb/s. That will be one more step away from this years target of 100/μb/s which will require 296 bunches.
To progress at each step when they add another 48 bunches, they need three fills and 20 hours of stable beams. At 152 bunches they had a rough time and ended up with only 16 hours, but they decided that was OK because that’s 20 in octal (I’m not making it up). The latest run at 200 bunches has gone very well with one run of 14 hours delivering 2/pb. Two shorter runs take the total time to over 20 hours so they are preparing for the next step.
To inject 248 bunches they need to switch to injecting 24 bunches in one go. If all goes well they should be ready to set the new record tonight. There is no sleep for the LHC.
The plot above shows the delivered luminosity for each experiment which is now between 12/pb and 13/pb for the big three. However, the experiments do not collect everything that is delivered. The plot below shows that ATLAS has collected 11.5/pb. I don’t have the equivalent plot for the other but it is likely that CMS and LHCb are also past the 10/pb mark at least.
Update (8 Oct 2010): 248 bunches now running with peak luminosity in ATLAS of around 88/μb/s
update (11 Oct 2010): There was a three day interuption to LHC opperations due to a problem with cryogenics and other niggles. They are now back up and have increase luminosity to 94/μb/s for the second run with 248 bunches. Remember, the target for this year is 100/μb/s, so nearly there!
update (12 Oct 2010): In a surprise move they have switched to a new filling scheme with 256 bunches giving 3% more collisions for ATLAS and CMS. If they get a good fill they might just reach 100/μb/s which means party time! If they don’t get there with this fill but they keep it going for a few hours they will be able to add 48 more bunches and that will certainly do it. Of course that might be someone elses shift 🙂