LHC Back With Gusto

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.

18 Responses to LHC Back With Gusto

  1. Luboš Motl says:

    Good news after that lazy week. ;-) My TRF sidebar currently says:

    highest luminosity:
     210/μb/s = 6.7/fb/year

    recorded luminosity:
     30/pb

    total collisions:
     2.1 trillion

    The numbers are per detector (CMS, ATLAS).

  2. Luboš Motl says:

    BTW I propose to switch to 1,000 times bigger units for the initial top luminosity, to avoid the annoying hard-to-type Greek letter. ;-)

    So the top luminosity so far is 0.21/nb/s.

  3. Philip Gibbs says:

    I can’t wait for the next physics conference. This one looks promising http://www.umich.edu/~mctp/LHC2010/prog.html

  4. Luboš Motl says:

    By the way, why do they consider 9 TeV and not the 10 TeV center-of-mass energy – with the latter figure’s having been studied at many places and papers previously?

  5. Philip Gibbs says:

    Good question. It may just be a question of how far they think they can go without taking extra risk. I know there are two problems which limit them from going all the way to 7+7 TeV, but they have said they think they could get to 6.5+6.5 TeV before it breaks. 5+5 TeV would be a nice round number though.

  6. Eric says:

    Is there some place on the web that publishes a schedule of past and/or future LHC runs and the energies generated?

  7. Kea says:

    Off topic … you’re getting a bit lazy with vixra uploads, no?

    • Philip Gibbs says:

      Sometimes I takes two to three days but it is always done. I have a lot of other things to do. Sometimes I dont get many papers for a while, then a whole lot at once, e.g. ten today.

    • Willard Mittelman says:

      The uploads for my articles and replacements (only four altogether, admittedly) have always been prompt, including a replacement today. Thanks so much for all you’re doing, Phil.

  8. [...] y en este momento están siendo barajadas varias opciones. Nos lo ha contado Philip Gibbs, “LHC Back With Gusto,” viXra log, 25 october [...]

  9. Kea says:

    Yeah, thanks Phil.

    I find this LHC progress both exciting and troublesome. At this rate, we only have a few months to figure out some decent post Tevatron spectra. We need all the string theorists to start working on Koide matrices ASAP …

    • Ulla says:

      I have thought of one thing. So many Nobelists can be linked to this new approach. This is something we have just not seen. It cannot be a mistake. But the scenario is breathtaking, an enormous task. We already have got those pictures from LHC. Look at them and compare to Keas approach. Just take a deep look.

  10. Luboš Motl says:

    We’re going for physics at 424 bunches per beam now! ;-)

    • Philip Gibbs says:

      Yes they tried it last night but lost the beams just at the end of the ramp, possibly due to beam gas scattering. They want to try again today. ATLAS now has nearly 40/pb which means they dont worry too much about collecting more data. Tomorrow they will try to use 50ns spacing. If it goes incredibly well we may see even more bunches before the end.

  11. Luboš Motl says:

    The LHC is now running two 3.5 TeV proton beams at 50 ns! ;-)

    • Philip Gibbs says:

      It’s a real bonus that they got to 50ns this year. I dont know if they will have time to reach a new luminosity record straight away. They failed to inject 424 bunches with 150ns spacing a few days ago but they might succeed with 50ns. The run with 109 bunches just ended, next they will try 205 then 400+ tonight. Luminosity was not looking optimal though.

      Even if they don’t get more luminosity today, this sets them up for a factor higher luminosities early next year, if the UFOs don’t get in the way. The experience of doing this now means that they can make better informed decisions during the winter break.

    • Philip Gibbs says:

      Apparently they are no longer UFOs, they are Ufinos :D, the superpartner to the UFOns maybe.

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