By Ron Cowen
After a year’s delay, the Large Hadron Collider near Geneva became the world’s highest-energy particle accelerator on November 30, revving up each of its twin proton beams to energies of 1.18 trillion electron volts. That smashes the record of 0.98 trillion eV held since 2001 by the Fermi National Accelerator Laboratory’s Tevatron in Batavia, Ill.
However, the researchers have yet to collide the beams at this record-breaking energy. So far, the highest collision energies at the LHC have only been 450 million eV.
The collision energies that the LHC can attain are critical for investigating the fundamental forces and particles in nature. That’s because the more powerful the accelerator, the heavier the particles it can produce. For instance, researchers hope the LHC may find the elusive Higgs boson, a proposed, extremely massive subatomic particle that, if found, would explain why elementary particles have the particular mass they do.
The Large Hadron Collider shut down for a year beginning in September 2008 — soon after its first collisions — when a faulty electrical connection between two magnets led to a leak of helium gas in a section of the accelerator.
Engineers restarted the collider on November 20, injecting the first beams since 2008 into the accelerator. The first low-energy collisions since the breakdown took place November 23 and were recorded by the accelerator’s four major detectors. Scientists hope to collide each beam at energies of 3.5 trillion eV by March 2010. The LHC won’t operate at its highest possible energy, corresponding to 7 trillion eV per beam, until 2011, said a spokeswoman from CERN, the European Organization for Nuclear Research, which hosts the LHC.
At the time of the electrical mishap last year, about 10,000 amps of current were flowing through the collider’s magnets. On November 30, when the collider’s proton beams achieved their record energy, only 2,000 amps flowed through the magnets, the spokeswoman said. A full 10,000 amps won’t circulate until early next year.
In addition to increasing the current, scientists are also working to collide the beams at higher intensities. So far, each colliding beam has contained only about 5 billion protons, but researchers ultimately want to achieve collisions with 110 billion protons per beam by early in 2010.
