Studies of the Cryogenic Part with Load Lock System T. Eisel, F. Haug CERN TE-CRG-CI October 19 th, 2011, Page 1 Superconductivity years Heike Kamerlingh Onnes (Leiden) 1908 liquefaction of helium 1911 electrical resistance measurements of mercury at low temperatures (< 4.2 K) 1913 Nobel Prize

Studies of the Cryogenic Part with Load Lock System T. Eisel, F. Haug CERN TE-CRG-CI October 19 th, 2011, Page 2 Bardeen –Cooper –Schrieffer (1957) – e - are fermions, Pauli exclusion principle – Energy reduction for F A Superconductivity Theory behind – BCS theory

Studies of the Cryogenic Part with Load Lock System T. Eisel, F. Haug CERN TE-CRG-CI October 19 th, 2011, Page 3 Cooper pairs – Between e - (different spin) – Attractive force (i + and e - ) – Positive charge attracts the following e - Time delayed due to heavy i + Large distance between the e - F C → 0 Energy drop for the e - of a Cooper pair Superconductivity Theory behind – BCS theory Presentation of P.Hedegard: “Theory_Behind”

Studies of the Cryogenic Part with Load Lock System T. Eisel, F. Haug CERN TE-CRG-CI October 19 th, 2011, Page 4 T C of pure metals: – 1.2 K – 4.15 K – 9.2 K Not superconducting: – Good normal electrical conductor (Cu, Ag, Au) – Ferromagnetic materials (Fe, Co, Ni) Superconductivity Energy gap, T C Superconducting Normal conducting

Studies of the Cryogenic Part with Load Lock System T. Eisel, F. Haug CERN TE-CRG-CI October 19 th, 2011, Page 5 Superconductivity Meissner Ochsenfeld effect Superconductor is diamagnetic – Shielding of external magnetic flux by electrical currents at its surface Transition to normal conducting state – For B ≥ B C → E kin,shield_e - ≥  – For both: shield current or transport current (j C )

Studies of the Cryogenic Part with Load Lock System T. Eisel, F. Haug CERN TE-CRG-CI October 19 th, 2011, Page 6 Superconductivity Types of Superconductors Type 1 Superconductor – Meissner phase Type 2 Superconductor – Shubnikov phase (alloys) – Magnetic flux is entering the superconductor in quantum (normal conducting islands) Meissner Shubnikov Normal conducting /10/07-01.html

Studies of the Cryogenic Part with Load Lock System T. Eisel, F. Haug CERN TE-CRG-CI October 19 th, 2011, Page 7 Superconductivity CERN: – electrical conductors (cables) at the LHC for magnets (di-, quadro- sextupol), cavities – NbTi (T C =9.2 K, B C2 =15 T; workhorse among superconductors) Else: – MRI (Magnetic Resonance Imaging) Tim Havens – GE Healthcare 1977 first clinical imaging, scanners worldwide in 2011, > 50% of superconductor worldwide, Script of TU Dresden – SQUID (Superconducting Quantum Interference Devices), – Transport (ship motor, train, centrifuge, clean room) – SMES (Superconducting Magnetic Energy storage) – FCL (Fault Current Limiter) is promising