Applications of Superconductivity - Civil Engineering (CE) PDF Download

Applications of Superconductivity
Superconducting Magnets:
We know that in ordinary electromagnet strength of the magnetic field produced depends on the number of turns (N) in the winding and the strength of the current (I) flowing through the winding. To produce strong magnetic field either N or I should be increased. If N is increased size of the magnet increases and if I is increased power loss (I²R) increases, which results in production of heat. Therefore there are limitations to increase N and I. If superconducting wires are used for winding in electromagnets, even with small number of turns strong magnetic fields can be produced by passing large current through the winding, because there is no loss of power in superconductors.

The type II superconductors, which have high H_c and T_c values, are commonly used in superconducting magnets. Ex: Niobium-tin, Niobiumaluminium, niobium-germanium and vanadium-gallium alloys.

The superconducting magnets are used in Magnetic Resonance Imaging (MRI) systems, for plasma confinement in fusion reactors, in magnetohydrodynamic power generation, in Maglev vehicles, etc.

Maglev Vehicles:
Vehicles, which float under the magnetic effect, are called MAGnetically LEVitated vehicles or simply MAGLEV vehicles. Such vehicle offer benefits like no friction, less power and noiseless transportation.

Cross section of the Maglev vehicle is as shown in the Fig 4.8. The system uses direct current superconducting magnets fixed under the carriage, which in turn induce eddy currents in the aluminium guide way. Eddy currents in the guide way generate repulsive force, which pushes the carriage up. Then forward motion of the vehicle is achieved by the principle of synchronous linear induction. The superconducting magnets and the cryogenic system for cooling the magnet are mounted below the carriage isolating them from the passenger compartment.

SQUIDS:
SQUID is an acronym for Superconducting Quantum Interface Device. SQUIDs are highly sensitive device, which can detect even weakest magnetic fields of the order of 10⁻¹⁴T. Squid is formed using two Josephsons junctions in the form of a loop. When a magnetic field is applied to this loop it induces circulating current in the loop which produces magnetic field which is just enough to exclude the magnetic flux inside the loop. It was found that the super current I_s induced in the loop is periodic in nature with the variation of applied magnetic field.

When squid is brought under the influence of an external magnetic field the flux through the loop changes and this causes the change in loop current. This variation of current in

the loop can be detected with the help of an induction coil kept adjacent to the loop. Thus SQUID can detect even a very sensitive magnetic field.

Squids are used to measure very small magnetic fields produced by heart and brain. They are used as voltmeter to measure the Hall effect and Thermoelectricity. They are used to detect ore and oil deposits