The flagship particle accelerator at the European Organisation for Nuclear Research is to be restarted in October, as opposed to September.
The Large Hadron Collider has been offline since an incident on September 19, when an equipment failure caused extensive damage. James Gillies, CERN's head of communications, said on Monday that an internal schedule set in February to restart the experiment has been pushed back by two or three weeks, but that the restart would still commence in the fall.
"The situation is a retreat from February," Gillies told ZDNet UK. "We had aimed for the end of September, but we're now looking at somewhere in October."
CERN has revised its LHC restart date a number of times. An original October 2008 estimate of an April 2009 restart was pushed back to the end of the summer, and was then revised to September.
The experiment, which is designed to improve scientific understanding of the nature of matter, had to be halted nine days after it was fully powered up, after an electrical malfunction caused a leak of liquid helium.
In May, details emerged that the malfunction had been caused by a faulty splice between two of the busbars that carry the superconducting cable in the LHC. Gillies said that the problem had not been in the design, but rather in the implementation of the electrical circuits for the quench system.
"It was a quality control flaw," Gillies said. "Most of the splices were done well, but a few of the solder joints were not perfectly carried out. We know there were a number of faulty splices in the machine. We've repaired a few, and we'll be repairing more."
CERN has developed noninvasive ways of testing the electrical circuits in some of the systems, which have remained cooled to 80 Kelvin (negative 315.67 degrees Fahrenheit), Gillies said. In circuits where faults have been found, Gillies said the surrounding sectors will be warmed to room temperature, and then the circuits will be repaired and tested again.
Gillies said CERN won't be able to give an exact restart date until August, when testing is completed. CERN has not decided whether to run the experiment at 4 teraelecton volts or at 5TeV. The world's most powerful particle accelerator, the Tevatron at Fermilab near Chicago, runs at 1TeV.
Tom Espiner of ZDNet UK reported from London.