THE EXCITEMENT may have died down but progress continues in efforts to start up the huge particle collider at the Cern complex near Geneva. Its operators are now well ahead of schedule in their attempts to achieve the first particle collisions in the machine by the middle of next month.
“There were hundreds of people in the control room yesterday but now it is down to those who are on shift,” said Cern’s head of communications James Gilles, adding that the commissioning programme had moved ahead of schedule.
“In the start-up schedule it was scheduled to take 31 days [before first collisions] but yesterday they got through days one to four so it is all going exceptionally well.”
The Large Hadron Collider (LHC), which ranks as the world’s largest single science experiment, only sent a bunch of particles on a first full lap of the 27km long beam channel on Wednesday morning.
This was repeated during the day, with bunches of particles sent round the LHC in a clockwise and then counter-clockwise direction.
The work continued into the night as the controllers injected a particle beam and circulated it for several hundred laps before stopping it, he said.
Ultimately the particles will be in a sustained circulation, completing more than 11,000 laps of the LHC circuit a second.
The plan was to follow yesterday’s progress by bringing in the LHC’s “radio frequency system”, Mr Gilles said. Radio frequency energy is used to speed up the beam but it also helps to keep the circulating bunches of particles in a tight group.
The work so far has involved sending single bunches of particles around the ring, each containing about one million particles, in this case protons. Mr Gilles said the radio system helped to keep the protons from spreading out along the beam line, holding them together over a space of about 20 to 30 centimetres.
The radio system holds the bunch together, while the powerful electromagnets installed around the LHC ring focus the bunch down to only half the thickness of a human hair and keep it in line and circulating smoothly around the beam channel.
Once in full operation, the beam will carry 2,808 separate bunches and each bunch will include 100 billion protons. The circulation tests proved the magnets can keep the beam contained and circulating while the radio system tests will show that the bunches can be prevented from spreading out along the beam. This involves the LHC making adjustments in as little as a billionth of a second to keep the particles in place.
The goal would be to “capture” the beam in this way, Mr Gilles said.
