CERN has announced that the Large Hadron Collider will initially run at an energy of 3.5 TeV per beam when it starts up in November, ending months of speculation about the LHC's restart energy, generated by the discovery of a number of bad connections between superconducting magnets in the machine. CERN completed tests on all 10,000 of the LHC's connections last week, and results indicate that no further repairs are necessary to run the machine safely.
"We've selected 3.5 TeV to start," said CERN's Director General Rolf Heuer, "because it allows the LHC operators to gain experience of running the machine safely while opening up a new discovery regime for the experiments."
Scientists on the LHC experiments, who will use the LHC's high-energy collisions to search for new discoveries about the nature of the universe, welcomed the planned initial run at 3.5TeV - half the machine's design energy.
"CERN has determined that the machine can operate safely at this level," said UCLA's Bob Cousins, deputy spokesperson for the CMS experiment. "At the same time, it’s an energy high enough to produce interesting physics and to start looking for discoveries."
The restart plan for the LHC includes first injecting and capturing beams in both directions--repeating the feat originally achieved on September 10, 2008. The beams will next be directed into collision at the injection energy of 0.45 TeV, and data will be collected by the LHC experiments for a day or two. Then the first acceleration of beam in the LHC will begin, with beams being taken up to world-record energies of 3.5 TeV and directed to collide. The first high-energy collisions are expected a few weeks after the restart process begins.
"We are eager get started," said Argonne National Laboratory's Tom LeCompte, physics coordinator for the ATLAS experiment. "The LHC gives us an extraordinary physics opportunity. There is plenty of good science we can do this year--the first year of what's probably going to be a more than ten year run for the LHC."
Scientists expect to run the machine for several months at this energy, giving accelerator physicists time to gain experience operating the LHC and the experiments time to collect a significant data sample. Then CERN will increase the beam energy towards 5.0 TeV for the remainder of the 2010 run. The first run of the LHC will end in late 2010, when work will start to prepare the machine to run at its full design energy of 7 TeV.
"CERN has done a stupendous job over the past year going over the machine making sure that all systems are in place to operate the LHC safely," said Fermilab Director Piermaria Oddone. " I am very optimistic that they will have an extremely successful run."
Preparing the LHC to run at its design energy will include additional repairs to the connections between superconducting magnets. More details about these repairs can be found in the full CERN press release.