As the Large Hadron Collider approaches its end of proton-proton physics for 2010, the CERN bulletin reports on some of the problems that have hit the final runs. One particularly frustrating issue concerns beam losses at the time of injection. X-rays of the injection point have revealed a “non-conformity” in the mounting of the interconnection.
Despite this they managed to reach peak luminosities of 148/μb/s last week, but not without difficulty. To run efficiently at this luminosity and higher they need to remove the obstruction so the collider has been closed down for four days while they try to fix it. This is a blow for their hopes to collect 50/pb this year. So far they have about 20/pb, but there are now just 13 days of running left until they start setting up for Heavy Ion physics on 5th November.
How much more data the experiments can get in time to show at the winter conferences will depend on how fast they can get back up to speed after this technical stop.
update 24-Oct-2010: The technical stop is now over and beams are once again colliding with 312 bunches giving peak luminosities of 152/μb/s. The plan now is to move to 360 bunches as soon as possible. After that they may just continue running at that level for the remaining 12 days to see how much physics data they can collect, or they may try injecting with 50ns bunch spacing and push for even higher bunch numbers.
update: ATLAS collected 4.3/pb on this run! Next run increases to 368 bunches.