Following a four-day technical stop to fix a restriction at the injection point, the Large Hadron Collider is back up and running with even more power. A few days before the stop they passed the target luminosity of 100/μb/s, but this morning they reached 206/μb/s. This is much better than expected and they are not finished yet.
Six weeks ago they had collected 3.6/pb and were at the end of a three-week commissioning phase for bunch trains. I predicted then that by the end of the pp run they would be collecting that much data in a single run. Yesterday they collected 4.2/pb in a single run of 10.5 hours with 312 bunches. In another run with 368 bunches still ongoing this morning, they have collected 3.8/pb in just 6.5 hours.
With 12 days left they could easily collect another 50/pb or more, but they have a long list of measurements and tests that need to be done. In fact their aim now is to switch to higher density bunch trains and push towards even higher luminosities. Going for higher intensities now is a good idea because new problems keep cropping up as they step up (e.g. the injection restrictions, UFOs and electron cloud background were only found at high intensity.) If they know about these things now then they have time to fix them properly while the machine is shut down during December to February.
Next year they aim to collect 1/fb of data per experiment. They can reasonably expect to have 200 days of running with pp collisions, so they need to be able to deliver 5/pb per day. The luminosities they have now reached mean that they can achieve this quite comfortably. In fact they have scope to increase luminosity by a considerable factor with tighter bunch trains and smaller beta*. When you do the maths, even peak luminosities approaching 1/nb/s are starting to look possible for early next year. How far they choose to go is up for discussion at a technical meeting in Evian in December.
This means that the target of 1/fb could be reached much sooner than expected in 2011. They will then have several options: They could close down early to ready the LHC for nominal energies of 7 TeV ahead of schedule, they could carry on and collect more data during the year, or they could aim for slightly higher proton energies straight away. Operation at 4.5 TeV per beam next year is a possibility already being considered.
Update: The latest fill ended with 6/pb collected by ATLAS.
On this version of the plan from a meeting this afternoon, they intend to run with the current 368 bunch scheme for three more days. This should take the collected data up to the 50/pb that the experiments were hoping for. If all goes well they can then spend the last week trying out 50ns separations which will allow them to push the bunch numbers over 400 for even higher luminosity.