Applications of Superconductor

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI), is primarily a medical imaging technique most commonly used in radiology to visualize detailed internal structure. and limited function of the body. By impinging a strong superconductor-derived magnetic field into the body, hydrogen atoms that exist in the body's water and fat molecules are forced to accept energy from the magnetic field. They then release this energy at a frequency that can be detected and displayed graphically by a computer. Magnetic Resonance Imaging (MRI) was actually discovered in the mid 1940's. But, the first MRI exam on a human being was not performed until July 3, 1977. And, it took almost five hours to produce one image.

Maglev Trains

Magnetic-levitation is an application where superconductors perform extremely well. Transport vehicles such as trains can be made to "float" on strong superconducting magnets, virtually eliminating friction between the train and its tracks. Not only would conventional electromagnets waste much of the electrical energy as heat, they would have to be physically much larger than superconducting magnets. A landmark for the commercial use of MAGLEV technology occurred in 1990 when it gained the status of a nationally-funded project in Japan. The Minister of Transport authorized construction of the Yamanashi Maglev Test Line which opened on April 3, 1997. In December 2003, the MLX01 test vehicle (shown above) attained an incredible speed of 361 mph (581 kph).

This is some example of levitation magnet using superconductor.

Properties of Superconductor

In superconductor, the superconductivity will happen when the temperature of the metal is achieved below the critical temperature. the value of the critical temperature or Tc is different from material to material. when the material is in superconducting states, the resistance in that material is zero. The simplest method to measure the electrical resistance of a sample of some material is to place it in an electrical circuit in series with a current source I and measure the resulting voltage V across the sample. The resistance of the sample is given by Ohm's lawas R = V/I. If the voltage is zero, this means that the resistance is zero and that the sample is in the superconducting state.

The table below shows the different of critical temperature between material.

What are the different between superconductor and normal conductor?

In a normal conductor, an electrical current may be visualized as a fluid of electrons moving across a heavy ionic lattice. When the current moving inside the material, the electrons are colliding between the ions in the lattice and some current is absorbed by the lattice. Because of the kinetic energy, some energy are converted into heat.

The situation is different in a superconductor. In a conventional superconductor, the electronic fluid cannot be resolved into individual electrons. Instead, it consists of bound pairs of electrons known as Cooper pairs. This pairing is caused by an attractive force between electrons from the exchange of phonons. Due to quantum mechanics, the energy spectrum of this Cooper pair fluid possesses an energy gap, meaning there is a minimum amount of energy that must be supplied in order to excite the fluid. Therefore, if ΔE is larger than the thermal energy of the lattice, given by kT, where k is Boltzmann's constant and T is the temperature, the fluid will not be scattered by the lattice. The Cooper pair fluid is thus a superfluid, meaning it can flow without energy dissipation.

The picture below show us one of the example of the arrangement of superconductor atoms.

History of Superconductor

Heike Kamerlingh Onnes (1913)

The first superconductor was found by Heike Kamelingh Onnes from Leiden University in 1911. the superconductivity was first observed in mecury when the resistance of the metal suddenly disappeared after he cooled it to the temperature of liquid helium, 4 degree Kelvin (-452F, -269C). Onnes won the Nobel Prize in physics in 1913.

Walter Meissner (1933)

In 1933, Walther Meissner have iscovered that a superconducting material will repel a magnetic field. This phenomenon is known as strong diamagnetism and is today often referred to as the "Meissner effect". The Meissner effect is so strong that a magnet can actually be levitated over a superconductive material

Brian D. Josephson (1962)

Brian D. Josephson is a graduate student at Cambridge University found that electrical current would flow between 2 superconducting materials even when they are separated by a non-superconductor or insulator. he had won a share of the 1973 Nobel Prize in Physics. This tunneling phenomenon is today known as the Josephson Effect.

K Alex Mueller (1987)

In 1986, K Alex Mueller had found a brittle ceramic compound that superconducted at the highest temperature then known: 30 K. He is a researchers at the IBM Research Laboratory in Rüschlikon, Switzerland.

In 1987, he achieved an incredible 92 K Tc. For the first time a material (today referred to as YBCO) had been found that would superconduct at temperatures warmer than liquid nitrogen - a commonly available coolant. Mueller won the Nobel Prize in 1987.

What is Superconductor?

Superconductor is a compound that will conduct electricity without a resistance below certain temperature. Resistance produce losses in the energy flowing through the material.

When an amount of current flow in a super conductor, the current will flow forever in a closed loop of superconductor material. Making it the closest thing to perpetual motion in nature. this is known as "macroscopic quantum phenomenon".