The mightiest accelerator at CERN, the European particle physics laboratory near Geneva, has rebounded from a fire that struck in May (Science, 23 May, p. 1183 ). Late last week, after an intensive effort to clean sensitive instruments coated with soot, physicists at the Large Electron-Positron collider (LEP) began their first experiments at enhanced power levels.
The fire took place on 13 May when a power supply for the accelerator shorted out, shutting down the Super Proton Synchrotron (SPS), which feeds particles to the LEP. At the time, the LEP was closed down for an upgrade. No one was injured, but smoke and soot coated a large amount of equipment. "The scale of the pollution from the smoke was a big surprise," says Roger Bailey, deputy group leader of the operations group for SPS and LEP.
After the fire, a team of 100 began a thorough cleaning. "They took everything into pieces, cleaned it, and put it back together again," says Bailey. Once the soot was removed, scientists returned to their task of upgrading the power of the accelerator's two colliding beams from 89 GeV (billion electron volts) to 91.5 GeV. "We are still increasing the energy by adding more superconducting cavities, and eventually we will reach 100 GeV per beam in 1999," says Luigi Rolandi, head of the ALEPH experiment, in which unexpected data from one of the four large detectors on the accelerator is being examined.
The increase in energy will help LEP create and study large numbers of so-called W particles, which convey the weak force responsible for radioactive decays. Another quarry is the Higgs particle, a particle that would give other particles mass and has yet to be observed. Many physicists hope that the enhanced LEP may inch just close enough to spot it.