Superconducting Magnet

CONSTRUCTION

Composition

Coil windings

The coil windings of a superconducting Magnet are made of wires of a type 2 Superconductor (e.g. Niobium-titanium ).

Coil

The coil itself is made of tiny Filament s (about 20 Micrometers thick) of a type II Superconductor , coated with Copper . The copper coating is needed for adding Mechanical Strength to the fiber, and in case the temperature rises above ''T''_c Or ''I''_c at which point superconductivity is lost. These Filament s need to be this small because in this type of superconductor, the current only flows skindeep.

Cooling

Liquid Helium is used as a Coolant for superconducting materials with critical temperatures around 4.2 K. Liquid Nitrogen is used for higher critical temperatures, or (being significantly cheaper) to cool a jacket around the helium.

Materials

The superconducting portions of most such magnets are composed of Niobium-titanium . This material has Critical Temperature of 10 Kelvin s and remains in this state until about 15 Tesla s. More expensive Magnets can be made of Niobium-tin (Nb₃Sn). These have a ''T''_c of 18 Kelvin s. When operating at 10 Kelvin s they are able to withstand a much higher Magnetic Field Intensity . Unfortunately, it is far more difficult to make the required filaments from this material. This is why sometimes a combination of Nb₃Sn for the high energy parts and Nb₃Ti for the lower energy parts is used.

USE

Superconducting magnets can reach a much higher Magnetic Field Intensity than normal Magnets and they can hold this field for a long time. This is particularly needed in Particle Accelerator s and Nuclear Magnetic Resonance . For economic reasons these magnets are also used when a field of more than 1 tesla must be maintained for a long time.

for Neutron Scattering .]]

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Superconducting Magnet