Avoid accidents with superconductive magnets in LHC. - PowerPoint PPT Presentation

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Avoid accidents with superconductive magnets in LHC. PowerPoint Presentation
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Avoid accidents with superconductive magnets in LHC.

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Avoid accidents with superconductive magnets in LHC.
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Avoid accidents with superconductive magnets in LHC.

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  1. Avoid accidents with superconductive magnets in LHC. What if protons collide with the magnets?

  2. An important diagram • Only under the 2  dimensional surface in a 3 dimensional space the material used for the wires of the magnets, niobium-titanium, is superconductive • This surface is determined by temperature, magnetic induction and current density. CERN HST 2001

  3. An important diagram(2) • To be save it is necessary to stay far from the surface, it limits current densities, magnetic induction and temperature. • In LHC B must be some 9 T, current some 13 000 A, so a temperature below 2 K is needed for safety reasons CERN HST 2001

  4. What happens if a proton hits the magnet? • Sometimes a proton could hit de side of the tube, hitting a superconducting magnet • The collision point heats up • This spot is no longer superconductive CERN HST 2001

  5. This means on the diagram • If the temperature of the spot rises higher than 5 K, Niobium-titanium no longer is superconductive. CERN HST 2001

  6. Catastrophy? • Heat due to Ohm’s law is generated • This causes the non-superconductive spot to become larger quickly, and more heat is generated • Etc... • The experiment breaks down CERN HST 2001

  7. Unless... • The heat of the initial collision spot is taken away. • Superfluid helium takes care of that: • it flows all over, the magnets swim in this fluid • the heat capacity of helium becomes larger with lower temperatures, one of the reasons why the temperature is so low CERN HST 2001

  8. As a consequence • The helium must flow constantly and cool permanently, taking the heat of accidental collisions away • The circuit should continuously be able to cool all helium to this low temperature • They will need 5000 tons of helium in this giant magnet, the production of the whole world during one year CERN HST 2001

  9. If this is not enough • The beam must be taken out of the tubes • A kicker magnet kicks the 2850 bunches of protons into a larger magnetic field, allowing the protons to bend into a pipeline of 100m long. • Another magnet disperses the proton bunches to bigger surfaces to collide with, the energy is absorbed by special materials (mainly graphite) at the end of the tunnel CERN HST 2001