LHC to Restart This Winter–at Half Capacity

The European Center for Nuclear Research announced today that when the Large Hadron Collider (LHC) goes online this November, it will be running experiments at half the energy it was designed for. This is in part because it is warming up, but it’s also a sign of bigger problems, according to the New York Times. At $9 billion, the LHC is the most expensive physics machine in the world and has been under development for 15 years. It was switched on nearly a year ago but has yet to collide any particles due to failed electrical connections. But a far bigger problem will remain after those connections are fixed–one that will prevent researchers at the accelerator from pursuing some of the big questions the machine was built to address, at least for a few years.

The LHC was designed to accelerate particles for extremely high-energy collisions, creating particles never before seen. These include the predicted Higgs boson–which, according to some physicists, gives other particles mass–and whatever it is that makes up dark matter, an unknown substance that constitutes 25 percent of the universe. But many of the LHC’s powerful magnets, which accelerate particles for these collisions, cannot operate at the energies for which they were designed and tested. Magnets have to be trained, pumped with higher and higher currents until they can handle tremendous energies. When the LHC’s magnets sat outside for some time between training and installation, a scientist told the Times, they might have lost this training. Until this is fixed, the accelerator cannot operate at its planned capacity of seven trillion electron volts.

The European Center announced today that the LHC will go online this November at 3.5 trillion electron volts until its operators gain experience, when it will be revved up to five trillion. At the end of 2010, it will be shut down to bring it up to the full seven trillion. However, even at 3.5 trillion, the LHC will be more powerful than today’s highest-energy particle accelerator, Fermilab’s Tevatron, which creates collisions at one trillion electron volts.

As Dennis Overbye reported in the Times, the decision to run the LHC at lower energies instead of first retraining the magnets was a tough one–and the decision illustrates how eager physicists are to tackle the really big questions. Overbye writes:

[S]ome physicists admit to being impatient. “I’ve waited 15 years,” said Nima Arkani-Hamed, a leading particle theorist at the Institute for Advanced Study in Princeton. “I want it to get up running. We can’t tolerate another disaster. It has to run smoothly from now.”

The delays are hardest on younger scientists, who may need data to complete a thesis or work toward tenure. Slowing a recent physics brain drain from the United States to Europe, some have gone to work at Fermilab, where the rival Tevatron accelerator has been smashing together protons and antiprotons for the last decade.