Increasing collision rate

1 April 2010 | By

Many collisions will be needed to unveil the secrets eventually hidden at the 7 TeV energy regime. Collisions are generated by the proton beams when crossing in the center of ATLAS after circulating in opposite directions inside the 27km vacuum pipes of the Large Hadron Collider. To increase the collision rate (or the luminosity as we call it) we have to concurrently play on three parameters: the beam intensity, the beam dimensions and the overlap of the two beams where they cross. The last parameter is the first to be optimized (and indeed it must be optimized from time to time depending on the LHC operation). This optimization has been done last night in ATLAS. It turned out the the beams were offset by slightly more than 0.1 mm. This may seem quite a small off-set after the 27 km trip around LHC, but putting them right head-on gave us an extra 60% collisions!

ATLAS 7 TeV Collision Events recorded, March 30th, 2010 (Image: Claudia Marcelloni/ATLAS)