LHC end of run troubles

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.

9 Responses to LHC end of run troubles

  1. Luboš Motl says:

    It’s annoying to see the “0 GeV, no beam” message… From a sociological viewpoint, it’s good to hear that the reason is not in vacations for their own sake but some technical glitch – that will hopefully be surmountable.

    So far, the highest lumo animosity 😉 was 150/ub/s, total collisions are 1.54 trillion, and 21.6/pb has been recorded, see atlas.ch

  2. Anders Lund says:

    It seems that the technical stop which was scheduled between the photon run and the ion run has been moved to this week, in order to cure the injection problems. This means that the photon run will be extended, and thus they will not loos days because of the technical stop. So the fact that they will have a hard time getting 50/pb is not because of the stop, but rather the problems they had getting stable beam last week.

    Cheers Anders

  3. Luboš Motl says:

    Around 2:30 in the morning, on Monday, the LHC began collisions with 368 bunches, achieving the initial luminosity of 215/ub/s or so!

    • Philip Gibbs says:

      The morning report said 206/μb/s. It’s much better than expected. I just did another post on it.

      • Luboš Motl says:

        Dear Philip, on the charts, ATLAS systematically has a higher luminosity than the CMS, by about 5 percent. I am confident that ATLAS will post it at least as 210/ub/s when they update their home page.

      • Luboš Motl says:

        Dear Phil, check atlas.ch now. The top luminosity has been updated exactly to 210/ub/s. Remember 1) I am always right, 2) if I am not right, then go the point (1). 😉

      • Philip Gibbs says:

        Yeah but there’s been another run since then 🙂

      • Luboš Motl says:

        But the other runs actually had a lower initial luminosity than the run we discussed at the beginning. Not sure whether they will show us graphs proving that.

      • Philip Gibbs says:

        I dare say you are right, although 2.1 could have just been 2.06 rounded up. 🙂 In any case it will be history if they ever get these 424 bunches in.

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