Sinclair- Applications

Question 1

Application of power lines

Answer 1

Significant amount of electrical energy lost as heat when using cables made of traditional metal conductors. SC can conduct electricity with 0 electrical resistance and so be vastly more efficient and can also carry much more current. SC câbles more expensive but could find applications in metropolitan areas as existing cable pits of conventional conductors are approaching full capacity

Question 2

Name the applications for high field magnets

Answer 2

Nuclear magnetic resonance (NMR) spectrometers.
Magnetic resonance imaging (MRI).
Particle accelerators.
Nuclear fusion.
Energy storage devices.
Transport.

Question 3

NMR and MRI

Answer 3

NMR can need 7, 14 and now 21.1T magnets. Is technique for studying chemical structure of large molecules like proteins. Very sensitive to protons.
MRI good at measuring proton density. Need large sized magnet for whole body scanners and large magnetic fields 3-8T. Most based on Nb-Ti coils

Question 4

Particle accelerators

Answer 4

Particles accelerated up to energies in TeV range. Need large magnetic fields to keep them on their trajectories. Easier when using high fields or for a constant energy the diameter of the accelerator can be made smaller using stronger magnets. LHC has thousands of magnets

Question 5

Nuclear fusion

Answer 5

Need to heat H2 to 10s of millions of degrees. Plasma consists of protons (H+) and electrons but can’t be kept in a material container. These charged particles can be bent by a strong magnetic field. Can retain particles in a suitable chamber in spite of their high velocity using sufficiently high magnetic fields of suitable geometry. Needs a SC magnet

Question 6

Energy storage devices

Answer 6

Use large coils to store energy in the form of magnetic fields. Can store 1-100MJ very effectively and deliver it back very fast with power in range of a few MW. Energy is stored with purpose of stabilising power supply in times of peak consumption

Question 7

Transport

Answer 7

Magnetically levitated (maglev) trains using SC magnets could be cheaper, faster and more efficient variants. High speed (550km/h Japan). Use SC coils mounted in trains that generate large magnetic fields (5T). Floats about 10mm above guideway on a magnetic field. Propelled by the guideway itself rather than onboard engine by changing magnetic fields. Magnetism switches for acceleration/deceleration. The electromagnets run the length of the guideway.

Question 8

Conductor requirements for power technology

Answer 8

Multifilament wires or tales that contain many SC filaments embedded in a normal metal such as Ag or Cu.
Need good mechanical and electrical properties (Jc>10^4A/cm2).
Need to carry large currents in small volumes and be cost competitive with existing technology (Cu wires).
Use in niche applications where high Tc have advantages over low Tc (like higher Jc and at higher fields compared with Cu (1-2T)).
Inexpensive refrigeration

Question 9

What is H*?

Answer 9

The irreversibility field. It is the point where resistance becomes finite and Jc vanishes. It depends on the crystal structure of the material and how well it has been processed. It between Hc1 and Hc2. If you go back down to 0T then SC will return.

Question 10

H* and BISCCO (2223) and YBCO

Answer 10

H* is much less than Hc2 for both because of their large anisotropy. H* is 0.2T at 77K for 2223 but could still be used for power cables as the self generated field is well below H* at 77K.

Question 11

What is true for all high Tc cuprates about their fields?

Answer 11

Hc2 and H* are lower for the field applied parallel to the c axis and perpendicular to the ab (SC) planes.
η=Hc2(para to SC layers)/Hc2(perp to SC layers)