LHC Update: Last proton run begins with better squeeze

The final proton physics run for 2011 is starting after the latest technical stop, and the plan is to go for a squeeze of beta* = 1m in place of the 1.5m used so far this year. This may mean it takes a little longer to get back up and running at full pace because of the change in the beam parameters, but once they are back to former bunch numbers, emittence and  intensity, the luminosity should pass 3.6/nb/s compared to the previous 2.4/nb/s record.

Further luminosity increases are possible by increasing bunch intensity again and I have seen 5/nb/s suggested as the target, but as always this will depend on how well the machine runs. We have seen it run supersmoothly for a week only to be followed by a week of long cryogenic outages, so I am going to give up on predicting total luminosities until it runs smoothly all the time, maybe.

However there will be eight weeks for this run and best performance has been about 400/pb per week, so make your own guesstimate.

Update: See also report at quantum diaries


13 Responses to LHC Update: Last proton run begins with better squeeze

  1. carla says:

    6 week slot in June they collected 1/fb, the following 6 week slot another 1.5/fb so 8 weeks they should collect between 2 and 2.5/fb giving a total of 4.5-5/fb which will be a fantastic achievement. Increasing the beam intensity by 1.5 doesn’t mean the average integrated luminosity increases by the same factor because of reduced beam half life: At 1/nb/s it was over 21 hours, whereas at 2/nb/s it was around 14 hours.

    Wasn’t 10/nb/s something they were going to achieve over a number of years after 2014? Seems incredible they’re talking of 5/nb/s this year which is 20 x 0.2/nb/s that was planned at the start!.

    • Philip Gibbs says:

      It depends how they increase luminosity. Emittance improvements only help the early part of the run because the emittence is eventually degraded by blow-up. Intensity increases also bring stability problems. However, the squeeze may not affect the beam so badly and the luminosity advantage may last for the whole run. I could be wrong.

      If it were not for problems with lost cryo etc they would have collected much more and could have easily been on target for 10/fb this year. However 5/fb is a great result and such problems are to be expected at this stage, so we shouldn’t moan.

  2. saibot says:

    We know that you’re fast, but 2012? Now you’re overdoing it ;)
    (Just a tiny typo.)

  3. briv1016 says:

    What’s the maximum luminosity before pile-ups become an issue? Also, do ATLAS and CMS have the ability to do lumi leveling?

  4. [...] al LHC. Sobre la reanudación de las colisiones en el LHC puedes leer a Philip Gibbs, “LHC Update: Last proton run begins with better squeeze,” viXra log, Sep. 2, 2011, y a Ken Bloom, “Coming attractions at the LHC,” US LHC [...]

  5. [...] al LHC. Sobre la reanudación de las colisiones en el LHC puedes leer a Philip Gibbs, “LHC Update: Last proton run begins with better squeeze,” viXra log, Sep. 2, 2011, y a Ken Bloom, “Coming attractions at the LHC,” US LHC Blog, [...]

  6. Tony Smith says:

    Phil, I just saw on LHC twitter that there are cryo problems with injection for the new run.

    You said that the LHC has “… run supersmoothly for a week only to be followed by a week of long cryogenic outages …”.

    Would it be a good idea to forget about improving performance and just go back to whatever was the machine state as of the supersmooth week ?

    Tony

    • Philip Gibbs says:

      Seems OK now and they are aiming for 36 bunches already.

      It is a tough call but I think they are right to push for higher luminosities as soon as possible. Even if it causes some hiccups early on it will highlight problems sooner that will need to be fixed eventually. Given that progress is well ahead of schedule they can afford to take that kind of risk for the long term advantage.

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