LHC Report: Towards stable beams and collisions

Over the past two weeks, the LHC re-commissioning with beam has continued at a brisk pace. The first collisions of 2011 were produced on 2 March, with stable beams and collisions for physics planned for the coming days.

Low intensity beams with just a few bunches of particles were used to test the energy ramp to 3.5 TeV and the squeeze. The results were successful and, as a by-product, the first collisions of 2011 were recorded 2 March.

One of the main activities carried out by the operation teams has been the careful set-up of the collimation system, and the injection and beam dump protection devices. The collimation system provides essential beam cleaning, preventing stray particles from impacting other elements of the machine, particularly the superconducting magnets. In addition to the collimation system, also the injection and beam dump protection devices perform a vital machine protection role, as they detect any beam that might be mis-directed during rare, but not totally unavoidable, hardware hiccups. In order to ensure this task is performed properly, they have to be carefully positioned with respect to the beam.

Teams were also busy preparing the bunch trains to be injected from the SPS into the LHC. The bunch spacing planned for this year is 75 ns and over the last days, operators have injected batches of 8 bunches with the nominal spacing. This is the first step towards the planned total of around 900 bunches per beam during the year.

The aim for the coming days is to complete the collimator set-up through the squeeze and in conditions for physics. After verification that everything is as it should be, the way will be open to first collisions and 'stable beams'. Initial runs will be with three widely-spaced bunches per beam as careful checks that everything is set-up properly continue.


by CERN Bulletin