LHC Report: Boost in bunches brings record luminosity

Having hit a luminosity of around 8.4x1032 cm-2 s-1 with 768 bunches per beam, the LHC went into a 5-day machine development (MD) program on Wednesday 4 May. Operators are now working on increasing the number of particle bunches in the machine towards a 2011 maximum of around 1380 bunches. The team is already hitting major milestones, recording another record-breaking peak luminosity on Monday 23 May.


Former LHC Project Leader Lyn Evans (to the right) and Laurette Ponce, the engineer-in-charge when the recent luminosity record was achieved.

The MD periods improve our understanding of the machine, with the aim of increasing its short- and long-term performance. This one also included tests of the machine’s configurations for special physics runs and a future high luminosity LHC.

It was an intense program and overall it went very well, with most measurements carried out successfully. Highlights included: commissioning a dedicated machine setup for TOTEM and ALFA; successfully colliding high intensity bunches with small transverse beam size, demonstrating the LHC's ability to push present parameters; and, an encouraging first look at a potential solution for the High Luminosity LHC (HiLumi-LHC).

This MD period led into a 4-day technical stop with the cryogenics, quench protection and other systems receiving some TLC (tender loving care). Quench tests were also performed to probe the potential for an increase in beam energy in the coming years. The technical stop was followed by a recovery period where a key priority was the careful validation of the machine protection system. On Sunday 15 May, a full set of luminosity (or Van der Meer) scans were performed. These are designed to allow the experiments to calibrate the measured luminosity - important input into analysis of the collected data.

Stable beams with 912 bunches were recorded on Sunday 22 May. The next day, the new peak luminosity record was brought to 1x1033 cm-2 s-1. Over the coming days, the LHC team aims to push the number of bunches towards a 2011 maximum of around 1380 bunches.


Mike Lamont for the LHC team