Cern collider ready for power-up

By Paul Rincon Science reporter, BBC News

The LHC has been in construction for some 13 years

Three decades after it was conceived, the world's most powerful physics experiment is ready to be powered up.
Engineers will attempt to circulate a beam of particles around the
27km-long underground tunnel which houses the Large Hadron Collider
(LHC).
The £5bn machine is designed to smash particles together with cataclysmic force, revealing signs of new physics in the wreckage.
This will re-create conditions in the Universe moments after the Big Bang.

But it has not been plain sailing; the project has been hit by
cost overruns, equipment trouble and construction problems. The
switch-on itself is two years late.

We will be looking at what the Universe was made of billionths of a second after the Big Bang Dr Tara Shears, University of Liverpool

The collider is operated by the European Organization for Nuclear Research - better known by its French acronym Cern.
The vast circular tunnel - the "ring" - which runs under the
French-Swiss border contains more than 1,000 cylindrical magnets
arranged end-to-end.
The magnets are there to steer the beam - made up of particles called protons - around this 27km-long ring.

Big Bang Day What is the Large Hadron Collider?

Eventually, two proton beams will be steered in opposite directions
around the LHC at close to the speed of light, completing about 11,000
laps each second.
At allotted points around the tunnel, the beams will cross paths,
smashing together near four massive "detectors" that monitor the
collisions for interesting events.
Scientists are hoping that new sub-atomic particles will emerge, revealing fundamental insights into the nature of the cosmos.
Major effort
"We will be able to see deeper into matter than ever before,"
said Dr Tara Shears, a particle physicist at the University of
Liverpool.
"We will be looking at what the Universe was made of billionths
of a second after the Big Bang. That is amazing, that really is
fantastic."
The LHC should answer one very simple question: What is mass?

LHC DETECTORS ATLAS - one of two so-called general purpose detectors. Atlas will be used to look for signs of new physics, including the origins of mass and extra dimensions CMS - the second general purpose detector will, like ATLAS, hunt for the Higgs boson and look for clues to the nature of dark matter ALICE - will study a "liquid" form of matter called quark-gluon plasma that existed shortly after the Big Bang LHCb - Equal amounts of matter and anti-matter were created in the Big Bang. LHCb will try to investigate what happened to the "missing" anti-matter

"We know the answer will be found at the LHC," said Jim Virdee, a particle physicist at Imperial College London.
The currently favoured model involves a particle called the Higgs boson
- dubbed the "God Particle". According to the theory, particles acquire
their mass through interactions with an all-pervading field carried by
the Higgs.
The latest astronomical observations suggest ordinary matter -
such as the galaxies, gas, stars and planets - makes up just 4% of the
Universe.
The rest is dark matter (23%) and dark energy (73%). Physicists
think the LHC could provide clues about the nature of this mysterious
"stuff".
But Professor Virdee told BBC News: "Nature can surprise us... we have to be ready to detect anything it throws at us."
Full beam ahead
Engineers injected the first low-intensity proton beams into the LHC in August. But they did not go all the way around the ring.
Now they will attempt to pass a proton beam around the full circumference of the LHC tunnel.
"We see how far the beam will go," said Steve Myers, head of the
accelerator and beams department at Cern, "we will try and make it go
round the full 27km sometime on Wednesday morning."







Superconducting magnets are cooled down using liquid helium












Engineers will be on the lookout for any potential problems: "There
are on the order of 2,000 magnetic circuits in the machine. This means
there are 2,000 power supplies which generate the current which flows
in the coils of the magnets," he told BBC News.
"If any single one of them has got the wrong polarity, or has
the wrong calibration constant, or whatever, then the beam will not go
round.
"If, in any of the channels [in the magnets], there is any
piece of debris - it is a very small channel - then the beam will not
go round."
Grabbing protons
Mr Myers has experience of the latter problem. While working on
the LHC's predecessor, a machine called the Large-Electron Positron
Collider, engineers found two beer bottles wedged into the beam pipe -
a deliberate, one-off act of sabotage.
The culprits - who were drinking a particular brand which
advertising once claimed would "refresh the parts other beers cannot
reach" - were never found.
If all goes well, and the beam makes one turn, engineers will
"close the orbit", allowing the beam to circulate continuously around
the LHC.
Engineers will then try to "capture" it. The beam which circles
the LHC is not continuous; it is composed of several packets - each
about a metre long - containing billions of protons.
The protons would disperse if left to their own devices, so
engineers use electrical forces to "grab" them, keeping the particles
tightly huddled in packets.
Once the beam has been captured, the same system of electrical
forces is used to give the particles an energetic kick, accelerating
them to greater and greater speeds.
After Wednesday's test, engineers will need to get two beams
running in opposite directions around the LHC. They can then carry out
collisions by smashing them together.
Long haul
The idea of the Large Hadron Collider emerged in the early
1980s. The project was eventually approved in 1996 at a cost of
SFr2.6bn.
However, Cern underestimated equipment and engineering costs
when it set out its original budget, plunging the lab into a cash
crisis.
Cern had to borrow hundreds of millions of euros in bank loans
to get the LHC completed. The current price is nearly four times that
originally envisaged.
During winter, the LHC will be shut down, allowing equipment to be fine-tuned for collisions at full energy.
"What's so exciting is that we haven't had a large new facility starting up for years," explained Dr Shears.
"Our experiments are so huge, so complex and so expensive that
they don't come along very often. When they do, we get all the physics
out of them that we can."
Steve Myers said engineers would break out the champagne if all
went to plan. But a particular brand of beer will not be on the menu,
he said.
Paul.Rincon-INTERNET@bbc.co.uk
http://news.bbc.co.uk/2/hi/science/nature/7604293.stm