3.magnetic levitation over a superconductor


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Magnetic levitation over a superconductor

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  • 1911 Onnes got Nobel prize for it Bednots and miller Bell labs Nobel prizes
  • 3.magnetic levitation over a superconductor

    1. 1. Magnetic Levitation Over a Superconductor
    2. 4. Evolution of superconducting materials with time Element / Compound T c Al 1 K Pb 7 K Nb 9 K Nb-Ti 9 K Nb 3 Sn 18 K Nb 3 Ge 23 K La-Sr-Cu-O 38 K Y-Ba-Cu-O 92 K Bi-Sr-Ca-Cu-O 110 K Tl-Ba-Ca-Cu-O 125 K Hg-Ba-Ca-Cu-O 165 K
    3. 5. <ul><li>Superconductivity history </li></ul><ul><li>Three Waves of Discovery of Superconducting Materials </li></ul><ul><ul><li>Normal superconductors - 1911 </li></ul></ul><ul><ul><li>Metals: Mercury, tin, lead, etc. </li></ul></ul><ul><ul><ul><li>Low Tc </li></ul></ul></ul><ul><ul><ul><li>Low Hc </li></ul></ul></ul><ul><ul><li>High-field superconductors - 1961 </li></ul></ul><ul><ul><li>Alloys: Niobium titanium, niobium tin, magnesium diboride (2001), etc. </li></ul></ul><ul><ul><ul><li>Low Tc </li></ul></ul></ul><ul><ul><li>High temperature superconductors - 1986 </li></ul></ul><ul><ul><li>Ceramics: bismuth strontium calcium & yttrium barium </li></ul></ul><ul><ul><li>copper oxides, etc. </li></ul></ul><ul><ul><ul><li>Low Jc (not inherent) </li></ul></ul></ul>
    4. 9. <ul><li>High Tc </li></ul><ul><li>Granularity </li></ul><ul><li>Large Anisotropy </li></ul><ul><li>Small coherence length </li></ul>
    5. 10. Melt Processed Nd-123 Excess Nd-422 precipitates - cause interfacial defects and aid flux pinning V. Seshu Bai et al. Eur. Phys. J. B 4 , 55 (1998)
    6. 11. <ul><li>Superconducting Magnets cooled by 77 K : </li></ul><ul><li>a) Trapped field magnets aimed at use in MRI </li></ul><ul><li> Being investigated at Cambridge, UK </li></ul><ul><li>b) Superconducting wires. </li></ul><ul><li>Superconducting Foam for use as Fault current limiters </li></ul><ul><li> being developed at Germany </li></ul><ul><li>Microwave cavities with High Q for finely tuned </li></ul><ul><li> communication devices </li></ul><ul><li>Magnetic bearings based on the large levitation force </li></ul><ul><ul><li>due to high Jc </li></ul></ul>Bulk Applications of RE-123
    7. 12. Nb 3 Sn Wire Fabrication Cu Ta-40wt%Nb Nb-1wt%Ti Sn-2wt%Mg
    8. 13. Shape Forming with high Jc IG processed Y- 123 cylinder Microwave Cavities Magnetic shields
    9. 14. <ul><li>Summary of classes of materials </li></ul><ul><ul><li>“ workhorse” LTS : NbTi </li></ul></ul><ul><ul><li>A15 class : Nb 3 Sn, Nb 3 Al, V 3 Ge, etc… </li></ul></ul><ul><ul><li>Medium T c HTS : BSCCO, MgB 2 , Chevrel phases </li></ul></ul><ul><ul><li>High T c HTS : YBCO </li></ul></ul>Vacuumschmelze 64000 filaments NbTi wire IGC 19 elements Nb 3 Sn wire
    10. 15. <ul><li>Example of Nb 3 Sn : NMR magnets </li></ul>NbTi Outer coils Nb 3 Sn Inner coils Potential upgrade to 1 GHz with BSCCO coils Systems used for chemistry, materials research, etc… NHMFL 900 MHz facility (21.1 T)
    11. 16. Magnetically Levitated Trains December 24,1997 Achieved world speed record for unmanned train 550km/h December 12,1997 Achieved world speed record for manned train 531km/h
    12. 17. Levitation Force on a magnet : Present experiment 1.Superconductor used : YBa 2 Cu 3 O 7-  … .. called (Y-123 compound) Melt-processed with extra Y 2 BaCuO 5 called (Y- 211 compound) T c = 92 K 2. Magnet used A permanent magnet SmCo 5 weighing ~ 8 gram
    13. 18. <ul><li>Measurements done </li></ul><ul><li>Zero field cooled : Levitation effect </li></ul><ul><li>a) Place the magnet on the pan of a balance </li></ul><ul><li>b) Keep the magnet far away so that H =0 and cool the superconductor from RT to 77 K </li></ul><ul><li>c) Note the change in weight of the magnet as the superconductor approaches it. </li></ul><ul><li>2. Field Cooled : Suspension effect </li></ul><ul><li>Repeat the above steps but ensure that the magnet is kept near the superconductor while it is getting cooled so that finite H exists. </li></ul>F d
    14. 19. <ul><li>Determination of T c : </li></ul><ul><li>Fix a thermocouple to the superconductor in order to measure the temperature of it </li></ul><ul><li>Cool the superconductor using liquid nitrogen (whose boiling point is 77 K) </li></ul><ul><li>Now levitate a magnet which signifies its superconducting nature </li></ul><ul><li>Record the temperature of the superconductor when the levitating magnet levitates no more </li></ul><ul><li>This recorded temperature will be the T c of the given superconductor. </li></ul>