LHC delivers 5/pb and accelerates plans

This week the Large Hadron Collider has been demonstrating unprecedented success and exceptionally smooth running. When the present fill is terminated at around 6pm European time the collision data delivered this year will amount to 5/pb. This has been achieved in the space of just 50 hours with a total time in stable beams of about 32 hours. During that time they have only experienced two significant problems; one unplanned dump and a brief loss of cryogenic status. Last year when the systems were being commissioned it was normal for every other attempt to reach stable beams to fail for some reason. In comparison we now see almost every fill being completed with a planned dump and no problems. This bodes very well for the 2011 physics runs and the beam team must be very happy with the LHC today.

At the end of the present fill using 64 bunches they should have the all clear to increase luminosity again. I am told that previous plans to go up in three steps at 104, 152 and 200 bunches have now been replaced with a two step plan at 136 and 200 bunches. This will probably require switching from the present 8 bunch injection to 24 bunch injection. At each step they need to complete three fills totalling 20 hours of stable beams. The new goal is to reach last year’s highest luminosity in just a few days so that the schedule can be brought forward. According to the draft schedule of last week they had intended to do an intermediate energy run during April. The purpose of this run is cross-calibration between proton and heavy ion collisions which requires a proton run at the same energy per nucleon as used for the lead ion runs last year. If possible this will now be brought forward to complete it before the scheduled technical stop on 28th March.

There is one other chore that must be undertaken before serious proton physics data taking can begin. There will be a scrubbing run during the first two weeks of April to clear the collider of dust particles and other unwanted effects. As far as I know this will still proceed as planned. This leaves 7 weeks of data collection before the “Physics at LHC 2011” conference. They should be able to deliver as much as 200/pb (or even more) in that time if everything continues to run as smoothly as it has his week. That’s enough to significantly advance the ongoing  searches for SUSY and other exotic physics.

Thanks to “pcatom” on the lhcportal forums for the detailed info

Update: A new run with 136 bunches is now in progress giving a peak luminosity of 150/μb/s


7 Responses to LHC delivers 5/pb and accelerates plans

  1. Luboš Motl says:

    Wel, if two days were enough for 5/pb, one year is equivalent to 180 times 5 i.e. 3.6/fb – which is OK but not excessively spectacular. I hope there will be more progress in the luminosity.

  2. Luboš Motl says:

    Sorry, I am an idiot, I meant 5 x 180 is 0.9/fb per year. That’s bad!

  3. Philip Gibbs says:

    Don’t worry, they are only at 64 bunches and will aim for 900 by the end of the year. It should be 200 in a couple of days. They are filling with 136 as we speak.

    Of course they wont run for anything like 365 days this year, more like 150

  4. Bill K says:

    The UFOs are still on holiday. But have no fear, they’ll be baack! Things are going rather well so far — ‘Latest News’ says 8.7/pb gathered during the past week.

    You know, what they could benefit from is a way to abort a ramp. Often, considerable time is spent stepping gradually all the way up to 3.5 TeV, sitting there awhile, then ramping gradually back down again — even when the beam had already been dumped way back at the beginning and the machine is empty.

  5. Philip Gibbs says:

    Now they have 10.7/pb

    The UFOs will show up more as the intensity increases, but perhaps they have taken other steps to avoid unnecessary dumps.

    Good point about the ramp. There must be some reason why they cant stop it. At least they can ramp up and down more quickly now

  6. Anders Lund says:

    They cannot stop the ramp if the beam is dumped, because the magnets has a property called Hysteresis (http://en.wikipedia.org/wiki/Hysteresis) which means that the behaviour of the magnets are not the same at 450 GeV if they have not been cycled through a full ramp down and pre-cycle.

    Also, thank you Philip for keeping us up to data on the progress.

  7. […] A few weeks ago I said the LHC should be able to deliver 200/pb before the conference. In fact they have already surpassed that figure for 2011 and can add last years 40/pb as well to make nearly 240/pb. I will also be tracking this number above. Two weeks ago I upped the estimate to 500/pb for the conference but even that is looking a little unambitious now. According to the plan there are about 30 days left for physics before the 6th June and they can now easily collect about 30/pb each day. My new estimate is at least 1000/pb which is 1/fb in time for the conference assuming they don’t lose too many days to machine development or faults. Recall that 1/fb is the official target for the whole of 2011! It may sound like their original expectations were a bit low but really this amazing result is due to the exceptional early performance of the collider when compared with previous models. […]

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