Category: Physics

[/caption]First there was a glitch with one of the huge 30-tonne transformers causing a delay of a few days, then a quench leaked a tonne of helium coolant into one of the tunnels, forcing a two-month shutdown while repairs could be made.

Brace yourselves for some more bad news.

In a statement released by CERN today, due to an obligatory maintenance period, the LHC will have to remain off-line until late March or early April 2009. Problems with an experiment as huge as the worlds biggest particle accelerator can be expected, but this will be a costly delay and a psychological setback after the initial excitement of the first particle circulation on October 10th. The elusive Higgs Boson will have to wait a few more months…

I had a nagging feeling over the weekend after writing about the LHC quench and the two month delay in operations – what if the delay is longer than we think? The severe damage was caused by faulty wiring between two supercooled electromagnets when scientists carried out electrical tests at the facility Friday morning, resulting in a helium leak between sections 3-4 of the 27 km (17 mile) accelerator ring. Although no one was injured, the emergency services had to be called and the electromagnets heated up well beyond operational temperatures. Initial reports suggested experiments would be put back until the end of the year, but now it would seem the LHC won’t accelerate particles again until spring 2009.

“Coming immediately after the very successful start of LHC operation on 10 September, this is undoubtedly a psychological blow. Nevertheless, the success of the LHC’s first operation with beam is testimony to years of painstaking preparation and the skill of the teams involved in building and running CERN’s accelerator complex. I have no doubt that we will overcome this setback with the same degree of rigour and application.” – CERN Director General Robert Aymar.

This is indeed a severe blow to CERN and the scientists at the LHC, but the delay is necessary as the time required to warm up the accelerator, fix the problem and cool it down again will extend into CERN’s obligatory winter maintenance period. Therefore we won’t see any more accelerated protons until 2009.

Once again, in light of these setbacks, physicists are keeping positive and hoping for success in the near future. “The LHC is a very complex instrument, huge in scale and pushing technological limits in many areas,” said Peter Limon in the CERN press release, who was responsible for commissioning the Tevatron at Fermilab in the USA. “Events occur from time to time that temporarily stop operations, for shorter or longer periods, especially during the early phases.”

There have been delays in the commissioning of the LHC (after all, it was originally planned to be operational in the mid-2000s) and setbacks in the last few days, but after two decades of planning and construction, a few more months isn’t that long in the grand scheme of things…

Source: CERN press release

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It’s this sort of news I really did not want to wake up to. At 0927 GMT Friday morning, a fault known as a “quench” resulted in the leakage of a tonne of helium coolant causing 100 of the LHC superconducting magnets to heat up 100°C. The fire services had to be called and it was some time before engineers could access the tunnels to assess the damage. It was worse than they were expecting. Although no one was hurt and there was no danger to the public, the once-supercooled magnets were one hundred times warmer than they should be and optimal vacuum conditions had been lost. To perform repairs, the rest of the damaged sector will need to be warmed up and then slowly cooled down again, resulting in a shutdown of LHC operations for at least two months…

The leak occurred between the Alice and CMS detectors (sectors 3-4) after repairs to the faulty 30-tonne transformer were being finalized and the systems were being powered up to begin a new series of commissioning tests. According to the LHC logbooks, temperatures rose by 100°C and the vacuum required within the equipment for particle circulation to be possible was lost. Engineers had to wait for oxygen levels to return to normal within the tunnels before they could investigate the “meltdown.”

Although last week’s fault with the transformer caused frustration, setting LHC experiments back by a few days, scientists were optimistic the incident would have minimal effect on the first scheduled particle collisions in October. Friday’s quench, however, is a serious incident, knocking the largest experiment mankind has ever attempted offline for at least two months. Although this is sad news, many scientists are keeping a positive attitude:

“This kind of incident was always a possibility with such a unique and demanding project, that’s why we were so tense on the 10th [of September]. Having seen those tantalising first signs of beam in our detectors, everyone is raring to go. So it’s really disappointing, and hard for us to keep in perspective right now. But a delay like this in a 20-year project isn’t an utter disaster and I’m sure the team at Cern will fix it, and make it more robust as they go.” – Prof Jonathan Butterworth of University College London, the UK head of the Atlas detector.

So what happened? The basic operating conditions for the LHC depend on very low temperatures and a very high vacuum state. It would appear both key conditions were lost as engineers tested the electrics of the LHC in the run-up to full commissioning. There was a faulty connection between two of the superconducting magnets, so when the system was switched on, the high current melted the connection, causing the helium leak. The loss of supercooled helium caused a rapid release of stored energy (an event known as a quench), heating the magnets and destabilizing the vacuum conditions.

After such a smooth start to the first proton circulation on September 10th, these setbacks may come as a surprise. However, probing the frontier of physics rarely happens without a few hiccups along the way, so let’s hope this incident will be the last and we can once again look forward to the first particle collisions toward the end of the year…

Sources: BBC, Telegraph

[/caption]According to reports, only a day after the first successful circulation of protons in the Large Hadron Collider (LHC) last week, operations at the world’s largest particle accelerator had to be stopped due to a fault with a 30 tonne transformer used to cool part of the facility. The protons were not being accelerated at the time and there was no risk to safety at the LHC.

Rather than maintaining the equipment below the operational 2 Kelvin, the transformer glitch caused temperatures to rise to over 4 Kelvin (which is still cold, after all it is only 4 degrees above absolute zero – but it’s not cold enough). The transformer failed after the successful anticlockwise circulation of protons on the evening of September 11th and rumours about LHC problems have only just been confirmed…

This was bound to be a frustrating problem for the LHC engineers, but in many respects it was inevitable. This is a facility more complex than any technology ever built; a 27 km ring of 1000 supercooled electromagnets, operating at a temperature colder than anything in the Universe, with 2000 separate power supplies and a vast number of synchronized detectors and sensors… it’s little wonder the LHC may experience one or two technical hitches.

“This is arguably the largest machine built by humankind, is incredibly complex, and involves components of varying ages and origins, so I’m not at all surprised to hear of some glitches. It’s a real challenge requiring incredible talent, brain power and coordination to get it running.” – Steve Giddings, physics professor at University of California, Santa Barbara

However, this fault was critical to LHC operations, ultimately shutting the experiment down until technicians find the problem. Judith Jackson, spokesman for the Fermi National Accelerator Laboratory, is not surprised the LHC should suffer the occasional setback. “We know how complex and extraordinary it is to start up one of these machines. No one’s built one of these before and in the process of starting it up there will inevitably be glitches,” she said.

Apparently, transformer malfunctions are commonplace in particle accelerators. “These things happen,” she said. “It’s a little setback and it sounds like they’ve dealt with it and are moving forward.”

According to CERN scientists, the proton beams made “several hundred orbits” clockwise and anticlockwise before the experiment had to shut down.

The Associated Press investigation into the September 11th transformer glitch indicates that the problem has been identified and CERN scientists are still on track for the first particle collisions in October.

Source: AP

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I apologize that Universe Today has been a little slow over the last couple of days. That’s because my webserver is completely bogged down with Google searchers worried that the world is going to end thanks to the Large Hadron Collider.

Don’t worry, it’s not. In fact, the twin proton beams fired for the first time today. Since you’re reading this, the Universe wasn’t torn apart.

But let’s just say that the Large Hadron Collider does create a microscopic black hole? What then… are we doomed? Nope. Ethan Seigel over at Starts With a Bang has done the calculations to figure out how massive a black hole would be created, and how much of the Earth it would consume if it fell down into the planet. He also calculates how long it should last before evaporating away. There you go, you can use these calculations to help your panicked friends realize there’s no need to worry about microscopic black holes.

Check out Ethan’s post, I won’t give away his final numbers.

And in a strange twist of irony, Google has changed today’s logo to celebrate the Large Hadron Collider. At least, that’s what I’m seeing here in Canada.

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We don’t mean to beat a dead horse – both Fraser and Ian have already covered this topic quite thoroughly — but just in case anyone still has any fears about the Large Hadron Collider meaning the end of the world, a new report published today provides the most comprehensive evidence available to confirm that the LHC’s switch-on, due on Wednesday next week, poses no threat to mankind. A copy of the report is available HERE. In a nutshell, it says nature’s own cosmic rays regularly produce more powerful particle collisions than those planned within the LHC, and nothing bad has happened to Earth from those quite natural and frequent events. The LHC will be studying nature’s laws in controlled experiments. So just relax and watch the LHC rap video.

The LHC Safety Assessment Group have reviewed and updated a study first completed in 2003, which dispels fears of universe-gobbling black holes and of other possibly dangerous new forms of matter, and confirms that the switch-on will be completely safe.

The report, ‘Review of the Safety of LHC Collisions’, published in IOP Publishing’s Journal of Physics G: Nuclear and Particle Physics, proves that if particle collisions at the LHC had the power to destroy the Earth, we would never have been given the chance to exist, because regular interactions with more energetic cosmic rays would already have destroyed the Earth or other astronomical bodies.

The Safety Assessment Group compares the rates of cosmic rays that bombard Earth, other planets in our solar system, the Sun and all the other stars in our universe itself to show that hypothetical black holes or strangelets, that have raised fears in some, will in fact pose no threat.

The report also concludes that, since cosmic-ray collisions are more energetic than those in the LHC, but are incapable of producing vacuum bubbles or dangerous magnetic monopoles, we should not fear their creation by the LHC.

LHC collisions will differ from cosmic-ray collisions in that any exotic particles created will have lower velocities, but the Safety Assessment Group shows that even fast-moving black holes produced by cosmic rays would have stopped inside the Earth or other astronomical bodies. Their existence proves that any such black holes could not gobble matter at a risky rate.

As the Safety Assessment Group writes, “Each collision of a pair of protons in the LHC will release an amount of energy comparable to that of two colliding mosquitoes, so any black hole produced would be much smaller than those known to astrophysicists.” They conclude that such microscopic black holes could not grow dangerously.

As for the equally hypothetical strangelets, the review uses recent experimental measurements at the Brookhaven National Laboratory’s Relativistic Heavy-Ion Collider, New York, to prove that they will not be produced during collisions in the LHC.

Source: EurekAlert