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LHC Report: Standing strong through the storms

As I write this report, the integrated luminosity counter for ATLAS and CMS is at 23.1 fb-1, exceeding our goal of around 18 fb-1


May 2018 was one of Switzerland’s warmest Mays since meteorological measurements started in 1864. However, it is not so much the temperature but the associated thunderstorms that can have an impact on our accelerator complex and, in particular, its subsystems. Météo France declared May 2018 the month with the most thunderstorms since records began in 2000.

Over the last few weeks, nearly every evening has been marked by thunderstorms of varying degrees of violence. This has caused regular temporary drops in voltage on the national power distribution networks, which have had an impact on our equipment, resulting in some systems switching off, while others suffered from digital communication errors, leading to malfunctions. So far this year, the CERN Technical Infrastructure operators have recorded twelve serious electrical disruptions, eight of which have occurred since the end of April.

In recent years, work has been undertaken to make our systems less sensitive to these electrical power glitches. As a result, their impact has been mitigated and the subsequent recovery has become more efficient. Despite the large number of thunderstorms and thanks to the efficient recovery work, the LHC and its injector complex are performing well and the beam availability ratios are not very different from previous years.

The volunteers of the Django Girls workshop attending the talk by the Deputy Head of CERN’s IT department, Maite Barroso Lopez
LHC time distribution over the period from 17 April to 7 June 2018. The most important figure in this pie chart is the stable beam statistic of 49.7%, which is very close to our goal of 50%. This can be achieved only when machine availability is high – for a machine as complex as the LHC, 80.7% is very good.

On Tuesday, 12 June, luminosity production was interrupted for a block of machine development sessions, during which no fewer than fifteen different aspects were addressed by experts. This will be followed by a four-day technical stop to perform the necessary maintenance, repairs and minor upgrades to the machine, as well as the experiments. Before resuming luminosity production on 4 July, the experiments will perform special physics runs, for which low luminosity is generally needed. Until then, the aim is to keep the luminosity production high – as I write this report, the integrated luminosity counter for ATLAS and CMS is at 23.1 fb-1, exceeding our goal of around 18 fb-1, while for LHCb, we are at 0.8  fb-1 with a goal of 0.6 fb-1.