China has created the world’s largest strong magnetic field, a technological breakthrough that paves the way for the construction of advanced medical scanning technology, according to the research team behind the feat.
The superconductive magnet, recently completed at the Chinese Academy of Sciences’ High Magnetic Field Laboratory in Hefei, Anhui province, has a field that can top 10 Tesla, about 200,000 times the earth’s magnetic field. It has an inner space 92cm in diameter.
By comparison, the superconducting magnet at the National High Magnetic Field Laboratory in Florida has an inner space just 2.5cm in diameter, and produces a field of just 3 Tesla.
It is more difficult to create and maintain a high, stable magnetic field in larger spaces.
“We have effectively caught up with the US and other developed countries in construction of the world’s most advanced magnets,” said Professor Gao Bingjun, a lead scientist. “Hopefully, we will overtake them in a few years’ time.”
The world record for the most powerful continuous magnetic field is held by the 45 Tesla, also in Florida. But Gao said it might soon be surpassed.
The Hefei team intends to put a smaller, more powerful water-cooled magnet inside the large 10 Tesla superconducting magnet to create a hybrid magnet which, with technical upgrades in the ensuing years, would generate magnetic fields stronger than 45 Tesla.
“Our goals is 60 Tesla,” Gao said.
Strong magnets play critical roles in scientific research and engineering problem solving. Researchers have discovered unknown physical properties by examining materials in high magnetic fields, leading to many applications, including miniaturising devices like mobile phones.
Stronger magnetic fields would also give physicists more a powerful tool to find the right materials to build quantum computers or high-temperature superconductive materials, allowing trains to exceed the speed of sound.
Another major application magnetic resonance imaging (MRI) in hospitals. When a patient enters an MRI scanner, the donut-shaped machine produces a magnetic field that stops the atoms in the human body from randomly spinning and reorients them to line up pointing either “north” or “south”.
When radio waves at certain frequencies are applied to the atoms, some resonate like strings being plucked by fingers, emitting radio waves that can be picked up by a detector to generate images of the inside of a body.
The stronger the magnetic field, the better the atoms can line up and the finer the resolution of the MRI image. It is believed that a 10 Tesla MRI scanner, which would not harm the body, could produce an image of an area as small as a tenth of a millimetre across, enough for scientists to examine neuron activities or heart disease in unprecedented detail.
There have been efforts to build large, powerful MRI scanners. In 2006, scientists in Britain and Germany launched a joint project to build the world’s most powerful MRI scanner, at 11 Tesla, but the machine has not been completed.
Gao said the magnets his team was working on could not be used directly for medical purposes, but the technology would lead to more powerful MRI scanners.
“With the next generation of MRI scanners we can see exactly what’s going on inside the human body, such as the thinking in our head and the metabolism in our stomach, like watching a high-definition movie,” he said.
However, researchers still have to solve many technological problems. For instance, existing coil materials lose their superconductivity beyond 20 Tesla, and metals inside the magnet would likely snap as they would not be strong enough to withstand the enormous force generated by a really powerful magnetic field.