For the past month there have been no physics runs at the Large Hadron Collider while the beam team prepare the systems necessary to start using higher intensity bunches of protons. The commissioning process is now deemed sufficiently complete and this evening they are making their first attempts to produce stable beams for physics runs with the new settings.
The current run has 3 bunches in each beam with about 90 billion protons per beam compared to just 20 billion the last time they did physics. With the new parameters they could achieve the highest luminosity yet seen at the LHC, but only if they can get everything perfectly tuned first time. More likely it will take a few shots to get there.
Getting to this point is an important milestone in the gradual buildup of the LHC’s power. From this point on further increases in luminosity this year will be gained mostly by adding more bunches into the beam. That is an easier process in principle, but they still have to take it slowly because the more energy there is in the beams, the more risk there is that components of the machine can be damaged if they lose control of them. By the end of the year there should be 240 bunches circulating in each beam, well on the way to the design limit of 2808.
Update: They did indeed reach stable beams with high intensity bunches for the first time. Luminosities of 2.5 x 1029 Hz/cm2 were reported which is about 20% up on the previous LHC record
Further Update: On a subsequent run over Saturday night they doubled the luminosity to 5 x 1029 Hz/cm2 The run lasted 14 hours and the integrated luminosity should be about 15 inverse nano-barns, enough to just about double the accumulated luminosity up to this point in one run (again!) To put this in perspective, the planned-for luminosity up to end of 2011 is 1,000,000 inverse nano-barns and that may still not be enough to find the Higgs boson. There is a long way to go, but this step up to nominal intensity bunches was one of the hardest challenges in the process of building up the power of the LHC.