LHC experiences close encounters with UFOs

On 29 May, yet another record was set as 1092 bunches per beam were injected into the LHC, hitting a peak luminosity of 1.26x1033 cm-2 s-1. While running at 3.5 TeV each beam now packs a total energy of over 70 MJ – equivalent to a TGV travelling at a 70 kph.


Operators in the LHC Control Centre happily show off their display screens after succesfully injecting 1092 bunches injected into the machine for the first time. 

As the total beam intensity has been pushed up, the LHC has encountered a number of related problems, such as the so-called UFOs (Unidentified Falling Objects). These are thought to be dust particles falling through the beam, causing localized beam loss. The losses can push nearby beam loss monitors over the threshold and dump the beam. This is more of an annoyance than a danger for the LHC, but UFOs do reduce the operational efficiency of the machine.

Despite this, the luminosity delivered to the experiments has steadily increased. On three occasions there have been over 40 inverse picobarns (pb-1) delivered in a single fill. The total for the year, at the time of writing, stands at over 800 pb-1 or 0.80 inverse femtobarn (fb-1) – well on the way to the target for the year of 1 fb-1. The program of the coming weeks is to push for even more luminosity, maximizing the total delivered to the experiments before the summer conferences.

by Mike Lamont for the LHC Team