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Video: Superconducting Levitating Train
|What is a superconductor?
Cross section of a 5% carbon-doped MgB2 wire taken with polarized light.
What is a superconductor?
Superconductors are materials that conduct electricity with no resistance. This means that, unlike the more familiar conductors such as copper or steel, a superconductor can carry a current indefinitely without losing any energy. They also have several other very important properties, such as the fact that no magnetic field can exist within a superconductor.
Superconductors already have drastically changed the world of medicine with the advent of MRI machines, which have meant a reduction in exploratory surgery. Power utilities, electronics companies, the military, transportation, and theoretical physics have all benefited strongly from the discovery of these materials.
A brief history of superconductors
The first discovery of a superconductive material took place in 1911 when a Dutch scientist named Heike Kammerlingh Onnes, who was also the first person to liquefy helium, and reached temperatures as low as 1.7 kelvin (K).
In the 1960s, two unrelated discoveries made closely together ushered in a new era in which practical superconducting devices were developed and commercialized: one was the discrovery of NbTi superconductor, which provided the first material for the practical manufacture of superconducting wire and shaped components; the second was the Josephson junction, which continues to provide the basis for a variety of unique electronic devices.
|To this day, the largest successful applications of superconductors remains the powerful electromagnets used in Magnetic Resonance Imaging (MRI) systems (over 22,000MRI magnets made) and research magnets, and the RF accelerator cavities used in high energy physics experiments.||Courtesy of Paul E. Debevec|
Despite the enormous success of NbTi and similar materials, even broader application of superconductors has been restricted by the requirement for cooling to very low temperatures (1.5 - 5K)using liquid helium.
In late 1986 J. Georg Bednorz and K. Alexander Müller, two researchers at IBM's Zurich Lab, discovered announced an oxide material that superconducted at 30K. These two researchers were awarded the Nobel Prize in Physics 1987 for their work. Then, in 1987, Paul Chu at the University of Houston discovered YBCO, which became a superconductor at just 90K. Because 90K can be reached using liquid nitrogen, a common industrial refrigerant, these discoveries opened up for the first time the potential for a much wider range of devices. Over the next several months, discoveries of BSCCO and TBCCO brought the transition temperature of superconductors up to 127K.
This discovery of these "High Temperature Superconductors" sparked vast interest, and an entire industry dedicated to the research and commercial development of these materials and their applications has emerged. Today, an enormous range of devices are under development for both low and high temperature superconductors.
International competition is strong in these materials, and current efforts involve many facets of the electronics, communications, power, medical technology, transportation, military, and materials processing industries.
|High Tc||Low Tc||Various Tcoptions|
|Medical||Magnet Resonance Imaging (MRI)||MRI|
|Various||Nuclear Magnetic Resonance (NMR)||NMR (inserts)|
|Industrial||MRI, NMR, etc.|
|Magnetic Separation||Magnetic Separation|
|Sensors and Transducers|
|Electric Power||Power Cables|
|Fault Current Limiters|
|Flywheel Energy Storage|
|Magnetic Energy Storage (SMES)|
|Transportation||Magnetically levitated trains|
|Marine Propulsion (motors)|
|Marine Propulsion (magnetohydrodynamic)|
|High Speed Computing|
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