Superconductors:

Superconductors are electric conductors that have no resistance to the flow of an electric current, and because of this no energy is lost as heat. They also exhibit strong diamagnetism (they are repelled by magnetic fields). There seems to by many advantages with such conductors, but do they really work or are they just another theory? If they are known to work, why don't we utilize them for everyday use? These are some of the questions I will try to answer, and I will begin where everything begun: in the beginning.

In 1911 the Dutch physicist Heike Kamerlingh-Onnes discovered that if mercury is cooled to about 4.2 Kelvin (-451.8° F) it becomes superconductive and will have no electrical resistance.

In 1933 the Germans Karl W. Meissner and R. Ochsenfeld discovered that a superconductor has a strong diamagnetic field, and if it's exposed to a "normal" magnetic field stronger than a critical value it will loose its superconductivity.

In 1957 John Bardeen, Leon N. Cooper and John R, Schrieffer, three American physicians put forward the BCS theory, which describes superconductivity as a quantum phenomenon. For this theory they was awarded the Nobel Prize in Physics in 1972.

In 1962 the British physicist presented his theory, which stated that there would be oscillations in the electric current flowing through two superconductors separated by a thin insulating layer in a magnetic or electric field. This later proved to be true and is known as the Josephson effect. He got half of the Nobel Prize in 1973 for his speculations.

In 1986 came one of the greatest breakthroughs in the field of superconductors. J. Goerge and K. Alex Müller at IBM Zürich Research Laboratory succeeded to get superconductivity in a ceramic material at the temperature of 30K (-405.67° F), and within a year other scientists had found resembling materials where a temperature of 100 K and rising were possible. In 1987 they was awarded the Nobel Prize in physics. The record for a superconductive material is now abour 140 K (-207,67° F)

Here is a table with superconductivity temperatures for some materials:

Now you should have a grasp of the history of superconductors. But the question is: what's the use of a conductor that has to have a temperature of 140 K? Is it not cheaper and easier to use conventional technology? I will write about the advantages and drawbacks with superconductors as they are today and as they are meant to be in the future.

The main advantages of the superconductors are their lack of electrical resistance and their diamagnetic field. Here are some examples where superconductors are/will be used:

• Wires made of superconductors would save energy (because of their lack of resistance), and because of this we could minimize the cost of producing, transporting and storing electricity. The environment would be spared on account of us using fewer power plants. Prototype cables are mainly being developed by Pirelli Cable Company and Southwire Company.
• Motors containing superconductors will be smaller and more efficient. Reliance Electric Company is developing a 400-horsepower motor.
• A generator with superconducting wire instead of iron magnets would be smaller and lighter than a conventional, and in this moment General Electrics are developing a 100-megavolt-ampere generator.
• Very sensitive measuring instruments e.g. for voltage and currents.
• Very high-speed trains that moves with almost no friction by using the diamagnetic properties of superconductors to repel a "normal" magnetic field. Magnetic trains have been under development in Japan for more than two decades, and prototypes have reached speeds of over 540 km/h (335,5 miles/hour).

The drawbacks are that even high-temperature superconductors has to have fairly low temperatures to work, they are difficult to manufacture in larger quantities and are still very sensitive to magnetic fields. They are also expensive. All this does that in most situations conventional technology is still better/cheaper, but those working with superconductors seems optimistic and prays for "the big breakthrough".

Now I'd like to introduce you to two companies/institutions that are researching and manufacturing superconductors and applications. One of them is the Swedish company Nutek, and the other is a collection of American companies that cooperate under the name DOE-SPI. Incorporated.

Nutek

Nutek thinks that Sweden has done well in the field of superconductors. They started to invest in this technology in 1988, after the big breakthrough for hightemperature-superconductors, and initiated many projects in cooperation with the industry. They have now extended their cooperation to other Nordic countries. The goal has been to develop hightemperature-superconductors, to optimize the properties of the materials and to make applications perform better.

To be able to pursue the research one has to have a very flexible organization, where the different project-leaders cooperate with each other and with other scientists. Furthermore the management have been cooperating with experts from other countries and participated in a couple of European projects.

Nutek are quite happy with what they have accomplished, for example one of the first RSFO-circuits (rapid single flux quantum), and hopes that it will soon be possible to manufacture superconductors that works in room-temperature.

The United States Department of Energy’s Superconductivity Partnership Initiative

U.S. Department of Energy (DOE) began to investigate the superconductor field of science in the same year as Nutek. Since the beginning they have invested in developing applications and wires for superconductors.

1993 they started the SPI (Superconductivity Partnership Initiative), and from the start they let people from all parts of the industry cooperate with the scientists, so that fresh ideas could be carried trough and tested. This is one of the reasons why DOE/SPI have become so proficient.

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