Description

Superconductivity is celebrating its 100th anniversary. This phenomenon, in which the electrical resistance of materials suddenly becomes zero when cooled, was discovered in Leiden in 1911 by Kamerling Onnes and his collaborators when they cooled mercury to near absolute zero. Meanwhile, superconductivity grew from a scientific curiosity to an actual application, for instance in MRI scanners.

Only after 1954 did people discover a class of practically applicable superconductors, such as NbTi and Nb3Sn, referred to as LTS (Low Temperature Superconductors) due to their transition temperature being below 20 K. A few years later, it was possible to produce LTS wires and use them to make powerful magnets without dissipation. In 1985, the HTS class was discovered (High Temperature Superconductors) with transition temperatures from =50 to =130 K, so still very low cryogenic temperatures contrary to what the name suggests

The presentation discusses properties of various superconductors and the resulting application areas.

MRI scanners were initially equipped with permanent or resistance magnets. But, due to the demand for stronger fields, MRI scanners now usually have superconducting magnets. Around 2,500 s.g. MRI scanners are sold annually worldwide, of which =600 are sold by Philips Healthcare. This makes MRI the largest user of superconductor. To illustrate, a 3 Tesla magnet contains more than 1 tonne of superconductor. A characteristic of superconducting MRI magnets is the strong magnetic field combined with very low energy consumption. There is no dissipation (current circulates infinitely in the short-circuited coil) and only 4 to 8 kW is needed to keep the magnet cold. Various aspects of superconducting MRI magnets will be explained.
In conclusion, superconductivity plays a crucial role in current MRI scanners.

Speaker(s)

dr Gert B. J. Mulder, Magnet expert at Philips Healthcare.

Location

Hall centre Prinsenhof, Hoofdstraat 43,

5683 AC Best

Organiser

Region South

Name and contact details for information

ing. Koos Mulder; t: (040) 2762182 or via the e-mail address below:

koos.mulder@philips.com