1 / 22

i r . Erwin Bielert Promovendus (PhD student) Universiteit Twente / CERN

Dutch Outreach Program Thursday March 10 th 2011 CSG Dingstede ( Meppel ), Het Loo /Huygens ( Voorburg ) and Celeanum (Zwolle) Superconducting Cables. i r . Erwin Bielert Promovendus (PhD student) Universiteit Twente / CERN. Contents. Why Superconducting Magnets? A Dutch Nobel Prize

alice-goff
Download Presentation

i r . Erwin Bielert Promovendus (PhD student) Universiteit Twente / CERN

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Dutch Outreach ProgramThursday March 10th 2011CSG Dingstede (Meppel), Het Loo/Huygens (Voorburg) and Celeanum (Zwolle)Superconducting Cables ir. Erwin Bielert Promovendus (PhD student) UniversiteitTwente / CERN

  2. Contents • Why Superconducting Magnets? • A Dutch Nobel Prize • What is a Superconductor? • Introduction to Electrodynamics • Superconducting Cables • Measurement Techniques (building 163)

  3. Why Superconducting Magnets? E goes up -> m larger -> F larger -> B larger Conventional magnets can make fields only up to about 2T

  4. A Dutch Nobel Prize • 1908: in Leiden, KamerlinghOnnes cools down helium to the point where it becomes a liquid • 1911: he uses cryogenic techniques to cool down mercury, tin and lead and finds that they loose their electrical resistivity • 1913: Nobel Prize in Physics “for his investigations on the properties of matter at low temperatures which led, inter alia, to the production of liquid helium”

  5. What is a superconductor?

  6. What is a superconductor? (1/6) • A material which has an electrical resistance of exactly zero and behaves like a perfect diamagnet(expelling all applied magnetic flux) CRITICAL TEMPERATURE Meissner-Ochsenfeld effect

  7. What is a superconductor? (2/6) T Tc B 0 Time -> Ideal conductor Superconductor

  8. What is a superconductor? (3/6) T Tc B 0 Time -> Ideal conductor Superconductor

  9. What is a superconductor? (4/6) Meissner State Normal State CRITICAL FIELD Mixed State Normal State Meissner State

  10. What is a superconductor? (5/6) CRITICAL CURRENT n=1 n=10 n=40

  11. What is a superconductor? (6/6) • The critical surface • Working point • Temperature margin • Stability • Quench

  12. Introduction to Electrodynamics

  13. Introduction to Electrodynamics (1/1)Steady Charges and Steady Currents • Coulomb’s law: • When the distribution of charges is known the electric field can be calculated • Biot-Savart law: • When the distribution of line currents is known the magnetic field can be calculated

  14. Introduction to Electrodynamics (2/2)Maxwell’s Equations Gauss’s Law Faraday’s Law No name Ampère’s Law Electric fields can be produced by charges or changing magnetic fields Magnetic fields can be produced by currents or changing electric fields

  15. Introduction to Electrodynamics (3/3)Field Properties • Divergence • Rotation Gauss’s Law: the flux through any closed surface is a measure for the total charge inside it is a tool to calculate electric fields Faraday’s law: a changing magnetic field induces an electric field (direction: Lenz law) Divergence of B: the magnetic field lines are closed loops and the density of the lines is a measure for the strength of the field Ampère’s Law: the field along any closed loop is a measure for the total current inside it is a tool to calculate magnetic fields and it shows that a changing electric field induces a magnetic field

  16. Superconducting Cables

  17. Superconducting cables (1/5)Material properties

  18. Superconducting Cables (2/5)Copper matrix – parallel path T<Tc T>Tc I I R=0 -> Ohm’s Law: V=0 -> P=0 R=large -> Ohm’s Law: V=large -> P=large -> DANGER I I R=small -> Ohm’s Law: V=small -> P=small -> safe operation R=0 -> Ohm’s Law: V=0 -> P=0

  19. Superconducting Cables (3/5)Filaments • Pure and large superconductors are vulnerable to heat generation caused by flux jumps: thin geometries are needed: filaments in the order of some μm are used • In accelerator magnets, field errors and energy loss are mainly determined by the filament magnetization: smaller diameters reduce this undesired behavior

  20. Superconducting Cables (4/5)Strand and Cables • High-field or high-current applications require conductors with fully transposed current paths (twisting) to ensure low AC-loss and homogeneous current density

  21. Superconducting Cables (5/5)Why twisting? • Particles are accelerated • The centrifugal force increases • The magnets have to deliver a larger Lorentz force • The current has to go up (changes in time) • A current is induced in the cables (surface!!!) • Jc is exceeded • Heating occurs • Quench!

  22. Measurement Techniques (building 163) The quality of a strand and cable can be checked by doing measurements: • Magnetization • RRR • Critical current • Minimum Quench Energy (MQE) The experimenter controls the testing conditions

More Related