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Engineering Challenges In Construction of LHC

Tuesday, October 07, 2008 1 comments


What will Future Archaeologist Make of This Megalomania

>>The Circular Underground Tunnel of LHC was not built now, it was a pre-existing one housing an earlier Large Electron Positron Collider (LEP) built in 1980 for peak energy levels of 209 gigaelectronvolts (GeV).
>>Since the energy of LHC was upto 14 (Teraelectronvolt) Tev, for using the same low energy experiment tunnel, much stronger Magnetic Field was needed to move much higher energy particle on the same tracks. But at the same time all the magnets and other equipment had to fit into the existing small bore-tunnel. Thus the coils of the magnet had to be cooled to much lower temperature (1.9K or -217.1C) so that more currents could be carried.
>>Alas at these temperature, the liquid Helium used for cooling is superfluid with nil viscosity (i.e. the liquid can climb up a wall). Therefore all welds and joints had to be of same standard as in a Nuclear Power Reactor.
>>The Detectors for the experiments - ALICE. ATLAS, CMS and LHCb were construted anew.
>>The magnets used for ATLAS are world's largest Supeconducting Magnets. The cavern needed for these is so large(35 M high)at 100M below earth - that due to Archimedes Principle it tries to rise towards surface of earth like a bubble at the bottom of lake - though only 0.2 millimetres per year. So the floor of the Cavern is 5 M thick concrete to avoid distortions during upward movement.
>>CMS actually rechecks the results of ATLAS by another technology. It has to be diametrically opposite to ATLAS. But at that point there were very fast moving underground acquifiers. To build cavern there, brine (salt saturated water) at -5C had to be pumped there for 6 months and then liquid nitrogen at -196C for one month to freeze water into a 3 metre thick ice-wall - which held back the water of the acquifier. Then only digging and construction could be done.
>>CMS magnetic field had to be stronger than even ATLAS. The magnet weighed 10,000 tonne. The coils therefore had to withstand the magnetic forces (=60 atmospheres)on each other.
>>To carryout any repair, 40,000 tonnes of equipment has to be allowed to heat back unaided to normal temperatures - that takes 5 weeks. Then after repairs 10,000 tonnes of liquid nitrogen and 130 tonnes of liquid Helium are needed to cool it back in another 5 weeks.
What will the future archaeologist make of this megalomania!!

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