by Physics Today

November 2, 2009

from PhysicsToday Website
 

Myers, director of accelerators at the CERN particle physics laboratory outside Geneva, is clutching a section of copper piping from which a flat electrical cable is protruding.

It looks unremarkable. Yet a piece of cable like this one was responsible last year for the world's most expensive short circuit.

More than $50 million-worth of damage was done to the Large Hadron Collider (LHC), the most advanced particle accelerator ever built, a few days after its ceremonial opening.

It has taken Myers - and hundreds of other CERN scientists - more than a year to pinpoint the guilty piece of cable and repair the wreckage.

"It was a very small piece, but it did immense damage," he said.

It remains to be seen whether Myers can fix CERN's tattered technological reputation in the process - when his team restart their great machine in a few weeks.

"I am not a nervous person," said the 63-year-old Belfast-born engineer. "And that is probably just as well."

Second Chance for Large Hadron Collider to Deliver Universe's Secrets
One Year After £30m Meltdown, 'God Machine' Is Ready to Run Again in Switzerland
by Robin McKie

Geneva
The Observer

November 1, 2009

from Guardian Website

The view from the central axis of the Large Hadron Collider.

Photograph: CERN
 

At first glance, the piece of metal in Steve Myers's hands could be taken for a harmonica or a pen. Only on closer inspection can you make out its true nature. Myers, director of accelerators at the CERN particle physics laboratory outside Geneva, is clutching a section of copper piping from which a flat electrical cable is protruding.

It looks unremarkable. Yet a piece of cable like this one was responsible last year for the world's most expensive short-circuit. More than £30m-worth of damage was done to the Large Hadron Collider (LHC), the most advanced particle accelerator ever built, a few days after its ceremonial opening.

It has taken Myers - and hundreds of other CERN scientists - more than a year to pinpoint the guilty piece of cable and repair the wreckage.

"It was a very small piece, but it did immense damage," he said.

It remains to be seen whether Myers can fix Cern's tattered technological reputation in the process - when his team restart their great machine in a few weeks.

"I am not a nervous person," said the 63-year-old Belfast-born engineer. "And that is probably just as well."

The LHC had been inaugurated at 9.30am on 10 September 2008 to a barrage of global media attention.

This was the God Machine that would unravel the secrets of the universe, it was claimed. Beams of protons, one of the key constituents of the atom's nucleus, were successfully fired round the machine's subterranean 18-mile circular tunnel under the Jura mountains outside Geneva.

Over the following weeks, it was predicted, scientists would recreate conditions that existed a trillionth of a second after the universe's birth and start making sensational discoveries as they smashed beams of protons into each other.

Discoveries would include the God Particle, a tiny entity also called the Higgs Boson, which is believed to give objects - including people - their mass.

In addition, dark matter, a mysterious, invisible form of matter that permeates the universe, would be uncovered, along with a host of other revolutionary discoveries.

"It was all looking so good," said Myers.

Then, at 11.45am on 19 September (2008), things went spectacularly wrong. Faulty soldering in a small section of cable carrying power to the machine's huge magnets caused sparks to arc across its wiring and send temperatures soaring inside a sector of the LHC tunnel.

A hole was punched in the protective pipe that surrounds the cable and released helium, cooled to minus 271C, into a section of the collider tunnel.

Pressure valves failed to vent the gas and a shock wave ran though the tunnel.

"The LHC uses as much energy as an aircraft carrier at full speed," said Myers. "When you release that energy suddenly, you do a lot of damage."

Firemen sent into the blackened, stricken collider found that dozens of the massive magnets that control its proton beams had been battered out of position.

Soot and metal powder, vaporized by the explosion, coated much of the delicate machinery.

"It took us a long time to find out just how serious the accident was," said Myers.

A 400-metre chunk of the £2.5bn device had been wrecked, it was discovered.

Worse, when scientists traced the cause to a tiny piece of soldering, they realized that they would have to redesign major parts of the collider's entire safety systems to prevent a repeat event. That has taken more than a year to achieve.

Now CERN scientists have begun firing protons round one small section of the collider as they prepare for its re-opening. Over the next few weeks, more and more bunches of protons will be put into the machine until, by Christmas, beams will be in full flight and can be collided.

The LHC will then start producing results - 13 years after work on its construction began.

"There was so much expectation that we were about to make great discoveries last year and then the accident occurred," said CERN researcher Alison Lister. "Morale was very low when we found out just how bad it was. However, we should now be getting results by Christmas, and you couldn't get a better present than that."

When fully operational, the LHC will soak up 10 times more power than any other particle accelerator on Earth, consuming 120 megawatts of electricity - enough for an entire Swiss canton - to accelerate bunches of protons, kept in two beams, each less than a hair's breadth in diameter, to speeds that will come "within a gnat's whisker of the speed of light", according to Myers.

One beam will circulate clockwise, the other anti-clockwise. Then, at four points along the collider's tunnel, the beams will cross.

Bunches of protons - each containing 100bn particles - will slam into other oncoming bunches, triggering collisions that will fling barrages of sub-atomic detritus in all directions.

These explosive interactions will form the core of the great collider's operations and will generate new types of particle, including the Higgs, that will pop fleetingly into existence before disintegrating into a trail of other sub-atomic entities. New physics will be uncovered with Nobel prizes following in their wake. And that is not all, say skeptics.

They argue that miniature black holes will be created and one of these could eventually grow to swallow up the Earth. The LHC would then not only be the world's biggest experiment - but its last. This fear has led protesters to make legal attempts to close down the LHC, one even making it to the European Court of Human Rights. All have failed, though one case - in Germany - has still to be resolved.

Even stranger is the claim by another group of physicists who say the production of Higgs bosons may be so abhorrent to nature that their creation would ripple backwards through time to stop the collider before it could make one, like a time traveller trying to halt his own birth.

"All Higgs machines shall have bad luck," said Dr Holger Bech Nielsen of the Niels Bohr Institute in Copenhagen.

Thus the cable meltdown that afflicted the LHC was an inevitable effect of the laws of time, a notion that leaves most CERN scientists scratching their heads in bafflement.

In fact, the real problem facing the LHC is simple. It is a vast device the size of London's Circle Line but is engineered to a billionth of a meter accuracy. Ensuring that no flaws arise at scales and dimensions like these pushes engineering to its absolute limits.

CERN almost succeeded last year. Now it is convinced that it has got it right this time.

"All I can say is that the LHC is a much safer, much better understood machine than it was a year ago," said Myers.

Most physicists believe he is right.

"If it works, we will have built the most complex machine in history," said one. "If not, we will have assembled the world's most expensive piece of modern art."

Scientists at CERN Hold Their Breath As They Prepare to Fire Up The LHC
If all goes to plan, beams of particles will begin whizzing around the LHC on Friday evening

for the first time since last year's explosion
by Ian Sample

Science Correspondent
18 November 2009

from Guardian Website

CERN scientists anxiously monitor their screens during the switch-on of the LHC in September last years.

Photograph: AFP
 

A giant scientific instrument that was designed to recreate the big bang but blew itself up in the process will be back in business on Friday.

Scientists at the Large Hadron Collider (LHC) at CERN, the nuclear research organization near Geneva, aim to have beams of subatomic particles whizzing around the machine on Friday evening, and will begin smashing them together soon after.

The first collisions will mark the end of a long and frustrating period for the researchers, who waited eight years for the machine to be built only to see it explode shortly after being switched on in September last year. Repairs and a new safety system cost an estimated £24m.

The machine, which occupies a 27km tunnel 100m beneath the French-Swiss border, will probe some of the deepest mysteries of the universe by crashing subatomic particles into one another at close to the speed of light.

The collisions are expected to reveal tantalizing signs of new physics that could include extra dimensions of space and "super-symmetry", a theory that calls for every particle in the universe to have an invisible partner.

Scientists also hope the machine will finally discover the elusive Higgs boson, aka the God Particle, which imbues other particles with mass. It may also expose the nature of dark matter, a mysterious, invisible material that stretches across the cosmos and collects around galaxies.

The £6bn machine was shut down last year after a spark caused by faulty wiring tore a hole in the collider and released liquid helium, wrecking surrounding equipment and encasing it in a layer of ice. Engineers have spent the past year checking the wiring in the rest of the machine and installing safety measures to prevent another catastrophe.

Work on the machine was interrupted earlier this month when a short circuit took out an electrical substation. The incident was blamed on a piece of baguette dropped by a passing bird.

The first collisions will be at low energies but will give scientists working on the machine's four giant detectors their first real data to work on.

Two beams of subatomic particles called protons, traveling in opposite directions around the tunnel, will be accelerated to almost the speed of light. At four points around the ring the beams will cross over, slamming the protons into each other head-on. The violent impacts will release fleeting bursts of energy that will recreate in microcosm the conditions that existed only a fraction of a second after the big bang.

Lyn Evans, who has overseen the construction of the LHC for the past 15 years, said CERN hoped to get two beams of protons circulating in the machine on Friday evening.

"Then we just have to steer them into one another," he said.

Collisions are expected to reach an energy of 2.2 trillion electronvolts by Christmas, enough for the LHC to take the title of the most powerful particle collider in the world.

By January, the machine should be running with at least three times as much energy as the current world-leading particle smasher, the Tevatron at Fermilab near Chicago.

"It's been a frustrating time, but what we do know is that the machine works beautifully," Evans said. "By Christmas, I expect we will take the high-energy frontier, if only by a whisker."

CERN engineers have already sent beams of particles half way around the machine. Their first goal later this week will be to circulate two beams of protons at low energy, the stage they reached this time last year before the machine exploded.

The first low-energy collisions will give scientists a chance to check the machine is working properly and ensure its detectors are recording the beautiful streaks of subatomic debris created when the particles crash into one another.

The machine will close for a couple of weeks over Christmas while engineers finish installing safety measures to prevent the machine exploding again when it is running at higher energies next year.

Jim Virdee, a physicist at Imperial College, London, and spokesman for the machine's giant CMS (Compact Muon Solenoid) detector, has spent the past year calibrating the detector by watching high-energy particles in cosmic rays hurtle through it.

"There's a mood of great anticipation here. We're cautiously optimistic and looking forward to finally getting going," he said. "We will soon be making great inroads into new territory. We'll be looking for new things, but what we find depends on how kind nature is to us."

Some scientists are relying on the LHC to pull physics out of at least a decade in the doldrums.

While theoretical physicists have pushed ahead with string theory and other models that describe the particles and forces of nature, experiments to prove any of them right or wrong have been lacking.

Last year, an American court dismissed a legal challenge that claimed the LHC might destroy the planet by creating a black hole or a clump of matter known as a strangelet. This year, physicists at the Niels Bohr Institute proposed an even more extraordinary possibility.

Their calculations suggested that the long-sought Higgs boson was so abhorrent to nature that any machine that tried to make it would be "sabotaged" from the future.

Few scientists are losing sleep over the prospect.

"We are absolutely and totally confident that the machine is perfectly safe, just as we were last year," said Evans. "And I'm not at all worried about the it being destroyed by its own future."