Physicists set the 'speed limit' for superconducting magnetic fields in the future

A team of researchers led by Northwestern University physicists has identified a high-temperature superconductor - Bi-2212 , a bismuth-containing compound that can be suitable for all types. New magnet wire, necessary to create the strongest superconducting magnet in the world, a magnet with a magnetic field strength of 30 tesla (magnetic induction unit, 1 tesla = 20,000 times the Earth magnetic unit).

The material currently used in magnetic resonance imaging in hospitals and laboratories - a low temperature superconducting niobium metal element - has been developed to the best, reaching about 21 tesla. No superconducting magnet wire can currently produce magnetic field strength of up to 30 tesla

(Artwork: scientificmagnetics) 'New material technology - like high-temperature superconducting technology - requires a leap from 21 tesla up to 30 tesla,' Mr. William P. Halperin, Weinberg College of Physics and Astronomy at Northwestern College of Science and Arts, who led the research, said: 'We have shown that Bi-2212 can operate at the same temperature. with the current temperature for magnets made of niobium - 4 degrees Kelvin - and also achieving the steady state needed to make a magnet with a magnetic field of 30 tesla . "

'We are exploring the limits of nature, and our discovery has very basic ideas for studying superconductors and for applications in magnetic field imaging photography,' he said. Halperin said. 'The dream is to have powerful magnets that don't require helium to cool. One day, new materials can be discovered at a level that exceeds the limit, but of course it cannot be done at the present time. '

A superconductor, when cooled to its proper temperature, will conduct electricity without resistance . Superconductivity first appeared in Bi-2212 at 90 degrees Kelvin, but Halperin and colleagues found that the steady state that requires a large magnetic field can only be produced when heat is lower than 12 degrees Kelvin. Halperin's team is the first team to set this limit for Bi-2212

'Sometimes what seems bad may be good,' said Mr. Bo Chen, author of the article. 'Our findings set a speed limit. If you exceed this speed, you may encounter problems. Knowing the temperature limit is a way to get safety. '

'To create a magnet with a magnetic field of 30 tesla, we need a superconducting material that can carry the necessary amount of electricity without exploding,' Halperin said. 'We found that the operating temperature for Bi-2213 must be below 12 degrees Kelvin. The good news is that this temperature can be achieved by cooling the magnet with a helium liquid. If we previously found the upper limit of 2 degrees Kelvin, it would be difficult to handle the frozen requirements. '

Magnetic resonance imaging is widely used in hospitals to diagnose medicine and scientists at universities, national laboratories and pharmaceutical companies even use additive technologies. enjoy stronger magnetic fields to study DNA, proteins and other complex molecules

About a dozen labs in the US are taking advantage of the largest magnetic field that has been put into use at a intensity of 21.1 tesla, this intensity produces a magnetic field 10 times stronger than the average machine in a hospital. Just increasing the field of magnets to a very small amount, from 21.12 to 22.2, will also increase the cost of the machine to $ 2 million.

'In magnetic resonance imaging, the larger the magnetic field, the higher the resolution, and can give scientists more detailed analysis. Magnets with a magnetic field of 30 tesla can greatly accelerate advances in chemistry, biology and medicine. ' Mr. Helperin said

By using magnetic resonance techniques at the National High School Laboratory in Tallahassee (Florida), Mr. Halperin and his team studied Bi-2212, one of the ' lovers ' of super though. To measure its properties, they introduced a rare oxygen isotope 17 - into the Bi-2212 crystal, which acts as a detector, very much like a fluorescent dye. They then decided on a phase diagram of the material, the position where the material achieved stability, which proved that it was impossible to achieve high temperatures and large magnetic fields at the same time.

'Since we now have Bi-2212 information, the question is,' Is it possible to actually create such a magnet? ' Mr. Halperin said. 'I don't really know - this depends on building and making materials to turn them into magnetic wires. My fellow scientists and engineers will solve these material problems and they don't like to accept 'no' answers to this question. '

Thanh Van