The latest from the LHC: a well-deserved break
A long and successful period of beam operation came to an end as scheduled on Monday 6 December . Since the first beam of 2010 was injected into the LHC on 28 February, a huge amount of progress has been made. After a technical stop of a few weeks coinciding with the end-of-year break, the LHC hardware systems will be restarted in January to be ready for the first beam of 2011 around 21 February.
The majority of the year has been dedicated to proton operation, with three distinct phases; (i) few (up to 13) low intensity bunches; (ii) a few (up to 50) high intensity bunches; (iii) many (almost 400) high intensity bunches using the bunch train scheme with 150 ns spacing. With peak luminosities of 2×1032
and almost 50 pb-1
of integrated luminosity delivered to the experiments by late October, attention switched to operation with ions, in November
After a rapid re-commissioning of the machine with ions, the physics run started on 8 November and continued for 4 weeks. The number of bunches was quickly increased to 121 per beam. Most of the run was made with this configuration, until the last weekend when the collider used 137 bunches per beam. During the last week, peak luminosities in excess of 3×1025
have been achieved and almost 10 µb-1
of integrated luminosity has now been delivered to the experiments.
While the LHC has achieved or exceeded all expectations for 2010, it should not be forgotten that this has only been possible thanks to the reliable performance of the injector chain. This is especially true for the ion beams, which underwent almost constant tuning in order to provide the beam quality required for the LHC. In particular, since the source has to be refilled with lead every 20 days, it then needs to be pumped, reconditioned and retuned to retrieve its performance. A shorted electrode in the source jeopardized the end of the run, but this breakdown was mitigated by a careful adjustment of the parameters, and by the implementation of a double injection into the LEIR machine, so that for the last fill of the year, as during most of the run, the bunch intensity was still 50% higher than foreseen in the design report.
by CERN Bulletin