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Superconductive magnets in LHC.

Superconductive magnets in LHC. The limits of traditional magnets force physicists to use superconducting magnets in LHC experiments. Special situations. The internal Weiss areas play a keyrole in this. The easier these align along the H-field, the bigger µ of the material

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Superconductive magnets in LHC.

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  1. Superconductive magnets in LHC. The limits of traditional magnets force physicists to use superconducting magnets in LHC experiments

  2. Special situations • The internal Weiss areas play a keyrole in this. The easier these align along the H-field, the bigger µ of the material • If H is very big, the increasing alignement of the Weiss areas slows down, because there are at a certain moment no more magnetic dipoles to align • In practice, B reaches a maximum value of 2T, increasing H does not help. CERN HST2001

  3. Limits • They use concrete to stabilize the form of the ferromagnetic yoke. • For a magnetic field of 0,3 T as in the LEP injection dipole magnet, you need a power of 20 kW per magnet. There are some 500 magnets in LEP, this means a total power for these magnets alone of 10 MW. CERN HST2001

  4. The cooling problem • They need lots of water to cool the magnet. • This is a enormous loss of energy. CERN HST2001

  5. One solution: superconductivity! • The LHC requires bending fields of 8,5T to 9T and even more. The current is 13000A • In and µ is constant, a yoke is necessary to make a strong construction, and to guide the return field. To have strong magnetic fields mainly the current should be increased to very high values. To avoid losses due to Ohm’s law-and the corresponding cooling problem- the wires must be superconductive: a temperature of 1,7 K. CERN HST2001

  6. The coil is now crucial. • Since the surface of the yoke no longer determines the form of the magnetic field anymore, only the form of the coil itself can. • The surface of the coil must lie perfectly horizontal, with a perfect vertical field. • This vertical field must be extremely homogenious. • The wrapping of the coil must be very precize: a tolerance of only a few µm is allowed, with a length of 12 meters. CERN HST2001

  7. The magnetic field • The field must also be very stable:constant electrical current • Both beams must be bent: the current goes through both coils (series) • For a vertical field the wrapping must be sinusoidal CERN HST2001

  8. Look carefully CERN HST2001

  9. More about wires CERN HST2001

  10. Cross section CERN HST2001

  11. CERN HST2001

  12. As a consequence • The helium must flow constantly and cool permanently, taking all the heat 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 HST2001

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