LHC Report: protons to the right, ions to the left please!

The LHC finished proton physics for the year on Sunday 30 October at 17:00 after delivering around 5.6 fb-1 to both ATLAS and CMS, 1.2 fb-1 to LHCb, and 5 pb-1 to ALICE.


A number of factors have contributed to these impressive totals, including: the increase in the total number of bunches to 1380 during the first part of the year, the high bunch intensity and small beam sizes delivered by the LHC injectors, and the very good aperture in the regions around ATLAS and CMS which have allowed a squeeze to beta* = 1 m. Despite some persistent issues, overall availability has been acceptable. About 25% of the programmed physics time was spent with stable beams - not bad at this stage in the LHC’s career given its complexity and the operation with high intensity beams.

Over the last two weeks, the luminosity delivery has been a bit fractured, with timeouts for tests with 25 ns beam, and with a high number of events per bunch crossing. The squeeze to 1 m in ALICE was also commissioned in preparation for the forthcoming lead ion run.

As of last Sunday, the LHC has been in machine development. An early high point was the cohabitation of protons and lead ions in the LHC - low intensity beams of protons (clockwise) and lead ions (anti-clockwise) were successfully injected and ramped together. A test of proton-lead collisions will be attempted for the first time in a couple of weeks. This coming weekend (5/6 November) set-up begins for the lead ion run. There is then a five-day technical stop starting on the Monday 7 November, followed by the 4-week ion run.

by Mike Lamont for the LHC Team