Registered: 28 Jul 2002
|The tremendous energy contained in the beams is so strong that stray particles could melt the superconducting magnets and damage or destroy the LHC. If enough stray particles hit the same magnet in succession, its operating temperature could raise from -271 degrees Celsius to 700 degrees in less than a second, causing a chain reaction as beams become unconstrained. As a result the ring is constantly monitored and as soon as temperature fluctuations occur a ‘quench’ is ordered which, in effect, causes the beams to be stopped and power to the affected magnets immediately cut. Then, to protect them, powerful heaters kick in and heat the 15 meter long magnets to 300 degrees Celsius in the space of two minutes. Beams have a maximum cycle life of about ten hours in the ring, and stopping them at the next cycle or if a quench occurs is another matter entirely – the energy contained in a single beam could melt through 40 meters of copper in less than a second. If this dissipation of energy occurred anywhere inside the ring, it would destroy whatever it penetrated. So, in a process known as ‘dumping’, beams are directed through exit segments in the ring by ‘kicker magnets’ that propel them into special dump blocks designed to absorb the energy. After first kicking them, the beams are then ‘diluted’ by a series of ten special magnets that scatter the beam and reduce its intensity by some 100,000 times. At this stage they’ll still bore a hole in most any substance, and so another set of magnets directs the diluted beam in a scanned pattern (similar to the way a CRT monitor is scanned) to dissipate heat over the surface area of what’s known as a dump block – a rather large eight meter long and one meter in diameter block of graphite composite, all secured within 1000 tonnes of concrete on all sides. Dumping takes just 80 millionths of a second, and heats the graphite to around 750 degrees Celsius in the process but does not melt it. |
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