Incident in the LHC - Sector 34

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Source: CERN
Content: Press Release
Date Issued: 20 September 2008
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Incident in LHC sector 34

Geneva, 20 September 2008. During commissioning (without beam) of the final LHC sector (sector 34) at high current for operation at 5 TeV, an incident occurred at mid-day on Friday 19 September resulting in a large helium leak into the tunnel. Preliminary investigations indicate that the most likely cause of the problem was a faulty electrical connection between two magnets, which probably melted at high current leading to mechanical failure. CERN[1]’s strict safety regulations ensured that at no time was there any risk to people.

A full investigation is underway, but it is already clear that the sector will have to be warmed up for repairs to take place. This implies a minimum of two months down time for LHC operation. For the same fault, not uncommon in a normally conducting machine, the repair time would be a matter of days.

Further details will be made available as soon as they are known.

Contact information:
James.Gillies@cern.ch
+ 41 22 767 4101

1 CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. India, Israel, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have Observer status.

CERN Opens Its Doors to the World - April 06, 2008

On 6 April 2008, CERN will open its doors to the public, offering a unique chance to visit its newest and largest particle accelerator, the Large Hadron Collider (LHC), before it goes into operation later this year. This scientific instrument, the largest and most complex in the world, is installed in a 27km tunnel, 100 metres underground in the Swiss canton of Geneva and neighbouring France. CERN will open all access points around the ring for visits underground, to the tunnel and the experiment caverns. On the surface, a wide-ranging programme will be on offer, allowing people to learn about the physics for which this huge instrument is being installed, the technology underlying it, and applications in other fields.

In the LHC, particles such as protons or heavy ions will be accelerated to close to the speed of light in two tubes. At four intersection points the particles will collide at an energy never before reached in a particle accelerator to study new areas of physics that so far have not been accessible. Experiments at the LHC expect to be able to answer a number of fundamental questions, such as the origin of mass or the nature of the so-called “dark matter”. However, since the LHC will explore a new energy range, there will also be unexpected results, resulting in new questions and new physics.

On the Open Day, many visitors to CERN will be able to descend and see the LHC and its big experiments, ALICE, ATLAS, CMS and LHCb in place in their underground caverns.

A central theme apart from the LHC, its magnets and experiments, will be superconductivity, the principle on which the operation of the LHC is based. At the heart of the LHC magnets lie 7000 kilometres of superconducting cables, cooled to a temperature close to absolute zero,
which are able to conduct electricity without resistance. Spectacular experiments, exhibitions and films will introduce the public to this exciting phenomenon, visitors will be able to meet physicists to “ask an expert” and there will be the chance for an encounter with two Nobel laureates who will give lectures about their prize-winning discoveries.

Research overturns accepted notion of neutron's electrical properties

For two generations of physicists, it has been a standard belief that the neutron, an electrically neutral elementary particle and a primary component of an atom, actually carries a positive charge at its center and an offsetting negative charge at its outer edge.

The notion was first put forth in 1947 by Enrico Fermi, a Nobel laureate noted for his role in developing the first nuclear reactor. But new research by a University of Washington physicist shows the neutron's charge is not quite as simple as Fermi believed.

Using precise data recently gathered at three different laboratories and some new theoretical tools, Gerald A. Miller, a UW physics professor, has found that the neutron has a negative charge both in its inner core and its outer edge, with a positive charge sandwiched in between to make the particle electrically neutral.

"Nobody realized this was the case," Miller said. "It is significant because it is a clear fact of nature that we didn't know before. Now we know it."

The discovery changes scientific understanding of how neutrons interact with negatively charged electrons and positively charged protons. Specifically, it has implications for understanding the strong force, one of the four fundamental forces of nature (the others are the weak force, electromagnetism and gravity).

The strong force binds atomic nuclei together, which makes it possible for atoms, the building blocks of all matter, to assemble into molecules.

"We have to understand exactly how the strong force works, because it is the strongest force we know in the universe," Miller said.

The findings are based on data collected at the Thomas Jefferson National Accelerator Facility in Newport News, Va., the Bates Linear Accelerator at the Massachusetts Institute of Technology and the Mainz Microtron at Johannes Gutenberg University in Germany.

The three labs examine various aspects of the properties and behavior of subatomic particles, and Miller studied data they collected about neutrons. His analysis was published online Sept. 13 in Physical Review Letters. The work was funded in part by the U.S. Department of Energy.

Since the analysis is based on data gathered from direct observations, the picture could change even more as more data are collected, Miller said.

"A particle can be electrically neutral and still have properties related to charge. We've known for a long time that the neutron has those properties, but now we understand them more clearly," he said.

He noted that the most important aspect of the finding confirms that a neutron carries a negative charge at its outer edge, a key piece of Fermi's original idea.

The strong force that binds atomic nuclei is related to nuclear energy and nuclear weapons, and so it is possible the research could have practical applications in those areas.

It also could lend to greater understanding of the interactions that take place in our sun's nuclear furnace, and a greater understanding of the strong force in general, Miller said.

"We already know that without the strong force you wouldn't have atoms -- or anything else that follows from atoms," he said.

Source: University of Washington

'Current' - Word of the Week

The term "current" in particle physics relates to the number of charged particles within an accelerator's beam and is expressed in "amperes." SLAC's SPEAR synchrotron at SSRL presently operates at a current of 100 milliamperes (one-tenth of an ampere), and the current must be topped off several times a day as the beam gradually loses electrons.
-Brad Plummer

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