Small Accidents Mean Big Trouble for Supercollider

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Fri Sep 26 01:02:07 CEST 2008


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Small Accidents Mean Big Trouble for Supercollider

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 Scientists expect startup glitches in the massive, complex machines
they use to smash atoms.

But the unique qualities of the world's largest particle collider mean
that the meltdown of a small electrical connection could delay its
groundbreaking research until next year, scientists said Sunday.

Because the Large Hadron Collider operates at near absolute zero —
colder than outer space — the damaged area must be warmed to a
temperature where humans can work. That takes about a month. Then it
has to be re-chilled for another month.



As a result, the equipment may not be running again before the planned
shutdown of the equipment for the winter to reduce electricity costs.
That means Friday's meltdown could end up putting off high-energy
collisions of particles — the machine's ultimate objective — until
2009.

"Hopefully we'll come online and go quickly to full energy a few
months into 2009 so in the long term, this may not end up being such a
large delay in the physics program," Seth Zenz, a graduate student
from the University of California, wrote on the site of the U.S.
physicists working at the European Organization for Nuclear Research,
or CERN.

"It's obviously a short-term disappointment, though, and a lost
opportunity," he wrote.

CERN spokesman James Gillies said the repair operation will last until
close to the usual winter shutdown time at the end of November. There
has been some discussion that the new equipment could operate through
the winter, but no decision has been made, he said.

The melting of the wire connecting two magnets Friday would have taken
only a couple of days to repair on smaller, room-temperature
accelerators that have been in use for decades, Gillies said.

Gillies said particle accelerators using superconducting equipment at
Fermilab outside Chicago and at Brookhaven National Laboratory in New
York state had similar problems starting up, but have been operating
smoothly since then.

"Once they settled in they seem to be pretty stable," Gillies said.

At the Sept. 10 launch of the collider, beams of protons from the
nuclei of atoms were fired first at the speed of light in a clockwise
direction though a fire-hose-sized tube in the tunnel. Then proton
beams were fired in the counterclockwise tube.

Jos Engelen, CERN's chief scientific officer and deputy director-
general, said the startup showed that the LHC can handle complex
operations.

"We have encountered a weakness in one particular connection during
very final hardware commissioning," Engelen told The Associated Press
by e-mail. "It is tough, but it can happen. We will make the repair
and resume the very successful operation of the accelerator."

A transformer failed outside the cold zone about 36 hours after the
collider's launch. That was repaired and the machine was ready again a
week after it was shut down.

But the goal of the LHC — shattering protons to reveal more about how
the tiniest particles were first created — was still weeks away
because the equipment has to be gradually brought to the higher
energies possible at full power.

"This was the last circuit of the LHC to be tested at high current
before operations," Gillies said. "There are an awful lot of these
connections between wires in the machine. They all have to be very
well done so that they don't stop superconducting, and what appears to
have happened is that this connection stopped being superconducting."

Superconductivity — the ability to conduct electricity without any
resistance in some metals at low temperatures— allows for much greater
efficiency in operating the electromagnets that guide the proton
beams.

Without the superconducting, resistance builds up in the wires,
causing them to overheat, he explained.

"That's what we think happened," Gillies said. "This piece of wire
heated up, melted, and that led to a mechanical failure."

Gillies said experts have already gone down into the 27-kilometer (17-
mile) circular tunnel under the Swiss-French border to inspect the
damage.

"By Monday I suspect we'll know more," he said.

Gillies said there is plenty for scientists at CERN to do between now
and the startup of experiments, including studying cosmic rays that
pass through collider's massive detectors.
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