Latest news from the LHC

Last week the LHC passed the threshold of 3 pb-1 total integrated luminosity delivered to the experiments, of which about half was delivered in just one week. These excellent results were achieved by operating the machine with up to 50 nominal bunches per beam.

After a very successful week that saw intense beams circulating for long periods (a total of 76.5 hours of stable beams, corresponding to about 40% of the time), there has been a technical stop this week. Over the coming days, experts will work on bunch trains with 150 ns spacing between bunches (the current minimum spacing is 1000 ns). This will involve making the necessary changes throughout the injector chain, as well as in the LHC itself. In the LHC, bunch trains imply working with a crossing angle throughout the machine cycle, in order to avoid unwanted parasitic collisions, which means that the whole process of injection, ramp and squeeze will have to be re-commissioned. The task also includes re-commissioning all the protection systems, both at injection and elsewhere in the cycle. This is particularly important now that the energy stored in each beam is about 3 MJ and is set to increase further in the coming weeks.

In parallel with these operations, the LHC teams will bring the higher speed energy ramp (10A/s) into operation, which will reduce the time needed to fill the machine.

The initial aim of this re-commissioning phase is to bring a few high intensity bunches in trains into collision for physics and later move from 50 up to 96 bunches injected in each direction. Once again, this should result in a significant increase in the luminosity delivered to the experiments.




by CERN Bulletin