A joint Fermilab/SLAC publication

This week at the LHC

A dimuon event recorded by CMS on December 14.

A dimuon event recorded by CMS on December 14.

The LHC had a successful weekend, with the experiments recording a total of 50,000 collisions at 2.36 TeV, the LHC’s maximum energy for 2009. Collectively, the six LHC experiments saw over one million collision events at 900 GeV, which also provided enough data to characterize the accelerator. Last night, the LHC circulated the highest intensity beams yet, with 16 particle bunches per beam. Each bunch contained approximately 20 billion particles.

The weekend’s collision events are an exciting confirmation of the machine’s abilities, but there is still a long way to go. This year's LHC run ends this week. The LHC will restart in the first quarter of 2010, following maintenance and hardware preparation for the next milestone, collisions at an energy of 7 TeV (3.5 TeV per beam).

“Our main goals for this year were to fully characterize the machine, have collisions at whatever energy to prove that they are feasible, and to try to increase the energy. Things for this year are on schedule,” explains Mirko Pojer of LHC operations. “To reach 7 TeV next year will be again a huge effort but increasing energy this year was easier than anybody was expecting. Ramping up in energy went very well.”

At the moment, many beam injections are essentially pilot runs. A beam with one particle bunch is sent around the ring at a low energy and intensity to probe that it can traverse the ring smoothly and that the entirety of the LHC is operating as one. In addition, the longevity of the beam is studied to assess how long the particles can circulate before decaying.

As plans are made to increase the accelerator’s energy and intensity in 2010, the balance of protecting the machine and maximizing scientific potential remains at the core of the decision-making process. The LHC will be switched off on December 16. CERN will close from December 19 to January 4. Following a period of hardware preparation and maintenance, the LHC will ramp even higher in energy, aiming for collisions at 7 TeV in the first quarter of 2010. The intensity will also be increased to the ultimate goal of 2808 proton bunches per beam, with 100 billion particles in each bunch.

Further LHC reading/viewing:

  • On Friday, December 18 at 6:15 a.m. Eastern time, the second public status report on the progress of the LHC and experiments will take place in CERN's Main Auditorium. The seminar will be webcast.
  • The ATLAS e-news provides an experiment’s perspective of the events over the last three weeks, plans for the next two months, as well as explaining what scientists are doing with these first LHC collisions at low energy.
  • You can follow events seen by CMS on their e-commentary, read more on CMS Times, and view event displays on the CMS public website

by Daisy Yuhas

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