The Large Hadron Collider (LHC) has become one of the coldest regions in the universe.
All eight sectors of the Large Hadron Collider have now been cooled to an operating temperature of 1.9 Kelvin (-271 degrees Celsius), which is lower than the temperature of outer space.
Sina Technology News — According to foreign media reports on October 20, Beijing time, after a cooling process, the highly anticipated Large Hadron Collider (LHC) has become one of the coldest regions in the universe. All eight sectors of the LHC have now been cooled to an operating temperature of 1.9 Kelvin (-271 degrees Celsius, -456 degrees Fahrenheit), which is lower than the temperature of outer space.
Large magnets are used to bend the particle beams around the LHC. These magnets utilize liquid helium to help the collider maintain this absolute low temperature. The LHC is located in a 27-kilometer-long circular tunnel deep underground on the Franco-Swiss border, with magnets placed from end to end throughout the tunnel. It is reported that the collider will restart in late November, and cooling it is a crucial step before the restart.
On September 19, 2008, the LHC was forced to shut down due to a so-called magnet “quench” that caused one metric ton of liquid helium to leak into the tunnel. Following the liquid helium leak, the collider had to be warmed up to reach the temperatures necessary for repairs. The LHC is the most powerful physics device ever built, capable of reconstructing the conditions of the early universe shortly after the Big Bang. It is operated by CERN (the European Organization for Nuclear Research) located in Geneva.
During the experiment, two proton beams will be guided through pipes passing through the magnets. Inside the circular tunnel, the proton beams will travel in opposite directions at speeds approaching the speed of light. At designated points around the tunnel, the high-energy proton beams will meet and collide. Scientists hope to discover new particles in the debris generated by these collisions to fundamentally deepen our understanding of the nature of the universe.
The operating temperature of the LHC is close to absolute zero, which is -273.15 degrees Celsius—the lowest possible temperature. In comparison, the temperature in remote regions of outer space is approximately 2.7 Kelvin (-270 degrees Celsius, -454 degrees Fahrenheit).
By design, the magnets used in the LHC are superconducting, allowing electric current to pass through with zero resistance, thereby minimizing energy loss. To achieve superconductivity, the magnets must be cooled to extremely low temperatures. For this reason, the collider employs a complex cryogenic circuit system using liquid helium as a refrigerant. To date, no particle physics research facility of this scale has operated at such low temperatures.
Before the proton beams can circulate through the 27-kilometer tunnel, engineers must test the collider’s new quench protection system and conduct magnet powering tests. Currently, the proton beams have been delivered to the “doorstep” of the LHC. It is reported that injecting a low-intensity proton beam into the collider will take at least a week. These initial tests involve only individual components of the collider rather than the entire circular tunnel.
Officials plan to have a proton beam circulate around the LHC tunnel in late November. Following this, engineers will conduct low-intensity proton beam collision experiments to provide scientists with their first set of data. The energy of the proton beams will then be increased for the first high-energy collisions. All of this marks the official launch of the LHC research program. High-energy collisions are expected to take place in December, but according to James Gillies, head of public relations at CERN, the collision schedule may likely be pushed back to January 2010.
Dr. Gillies stated that operating this accelerator is a very delicate task. “While accelerating the proton beams, you have to be deeply concerned about the distance between them. But when you want them to collide, you want them to be as close as possible.” He noted: “If an error occurs, you could lose the proton beam. The entire process takes some time to reach perfection; after that, all you have to do is wait for the collisions to happen. We can understand the distance between the final control elements of the collider and the collision point as being somewhat like two knitting needles, one on each side of the Atlantic, being made to collide.”
Officials plan to take a short break during the Christmas and New Year holidays, during which the laboratory will be closed. Although management has discussed how to complete relevant work during this period, Gillies mentioned that logistical support is a very complex task. The main factor prompting the decision for a winter shutdown is worker contracts, which would require renegotiation.
Officials stated that the upgrade of the early warning system (quench protection system) will prevent accidents similar to the 2008 shutdown from recurring. This upgrade includes the installation of hundreds of new detectors around the collider. Following the 2008 accident, CERN invested approximately 40 million Swiss francs (24 million GBP) to repair the LHC, which included upgrading the quench protection system. (Xiao Wen)
Source: http://tech.sina.com.cn/d/2009-10-20/07043520176.shtml
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