Superconductors are materials that conduct electricity with zero resistance when cooled below a critical temperature, and they show up in more places than most people realize. They’re inside every MRI scanner, they power the world’s fastest trains, and they form the backbone of quantum computers. Here’s a closer look at the major applications.
MRI Scanners and Medical Imaging
The most common encounter most people have with superconductors is inside an MRI machine. Clinical MRI scanners use large superconducting magnets to generate a stable magnetic field of 1.5 tesla, roughly 30,000 times stronger than Earth’s magnetic field. That powerful, uniform field is what allows the scanner to produce detailed images of soft tissue, organs, and joints. Without superconducting magnets, generating and sustaining that kind of field strength would be wildly impractical in terms of both energy consumption and heat.
Beyond standard MRI, superconductors enable an even more specialized sensor called a SQUID (superconducting quantum interference device). These sensors can detect magnetic fields at the femtotesla level, which is roughly a billion times weaker than what a fridge magnet produces. That sensitivity makes them useful for magnetoencephalography, a technique that maps brain activity by picking up the tiny magnetic signals generated by neurons firing. Researchers are also working on combining this brain-mapping capability with ultra-low-field MRI into a single hybrid system.
High-Speed Maglev Trains
Japan’s SCMaglev is the fastest train ever built, and it runs on superconducting magnets. In 2015, a test run hit 603 km/h (375 mph), a record certified by Guinness World Records. The system’s planned operating speed is 500 km/h (311 mph) for passenger service.
The train floats above the track entirely. Superconducting magnets mounted on the train pass over coils embedded in the guideway at high speed, which induces electric currents in those coils and turns them into temporary electromagnets. The interaction creates both lift and lateral guidance. If the train drifts to one side, the coils on the far side pull it back while the closer coils push it away, keeping it centered automatically. Because there’s no physical contact between the train and the track, there’s no friction from wheels or rails, which is what makes those extreme speeds possible.
Particle Accelerators
The Large Hadron Collider at CERN uses 1,232 superconducting dipole magnets to bend beams of protons around its 27-kilometer ring. Each magnet is 15 meters long, weighs 35 tonnes, and generates a magnetic field of 8.3 tesla, more than 100,000 times stronger than Earth’s. Those fields are what keep particles on their circular path at near-light speed. Conventional electromagnets simply can’t produce fields that strong without melting from their own resistive heating, which is why every major particle accelerator built in the last few decades relies on superconducting technology.
Quantum Computing
Most of the quantum computers built by major tech companies use superconducting circuits as their qubits, the quantum equivalent of a classical computer’s bits. The key component is a tiny device called a Josephson junction, which is a thin insulating barrier sandwiched between two superconductors. This junction behaves like a nonlinear electrical element, and that nonlinearity is what makes it useful. A simple superconducting loop would act like a basic oscillator with evenly spaced energy levels, which isn’t helpful for computation. The Josephson junction breaks that even spacing, creating two distinct low-energy states that can represent 0, 1, or a quantum combination of both. That’s the foundation of a qubit. These circuits must be cooled to temperatures near absolute zero (around 15 millikelvin) to maintain their quantum properties.
Power Transmission
Conventional copper and aluminum power lines lose up to 10% of the electricity they carry as heat, simply because the metal resists the flow of current. Superconducting cables eliminate nearly all of that waste. In one study modeling power delivery to a 100-megawatt data center, superconducting cables reduced total transmission losses to just 1.7% of what conventional cables would produce. Over a 10-year period, the superconducting system was also cheaper overall despite higher upfront costs, because the energy savings accumulated year after year.
High-temperature superconductors have made this more feasible. These ceramic materials lose all electrical resistance near the boiling point of liquid nitrogen, around minus 196°C. Liquid nitrogen is far cheaper and easier to handle than the liquid helium required by older superconducting materials, which need to be cooled to minus 269°C. For power cables, the nitrogen circulates through the cable’s cooling system and is periodically rechilled, keeping the superconductor well below its critical temperature.
Energy Storage
Superconducting magnetic energy storage (SMES) systems store electricity as a magnetic field inside a superconducting coil. Because the coil has no resistance, current circulates indefinitely without losing energy. When power is needed, the system can discharge in under 100 milliseconds, far faster than batteries or most other storage technologies. The expected round-trip efficiency for a large unit is 90% or greater. That combination of speed and efficiency makes SMES particularly useful for stabilizing power grids during sudden demand spikes or brief outages, acting almost like a shock absorber for the electrical grid.
Fusion Energy
The ITER experimental fusion reactor, currently under construction in southern France, depends on some of the largest superconducting magnets ever made. Fusion works by confining a plasma heated to hundreds of millions of degrees inside a magnetic “cage” so it never touches the reactor walls. Creating that cage requires enormous magnetic fields sustained continuously, something only superconducting magnets can do efficiently.
ITER’s magnet system uses two superconducting materials. The toroidal field coils and the central solenoid (the vertical column at the reactor’s core that drives plasma current) are wound from niobium-tin strands. The poloidal field coils, which shape and position the plasma ring, use niobium-titanium. All of these magnets operate at around 4 kelvin (minus 269°C), cooled by supercritical helium. The central solenoid alone is built from six stacked coil packs and functions as the backbone of the entire magnetic confinement system.
Ship Propulsion and Industrial Motors
Superconducting electric motors can generate the same power as conventional motors in a fraction of the size and weight. This matters most in applications where space and mass are at a premium, like naval ship propulsion. Military and commercial ship designers have explored superconducting motors because a smaller, lighter motor frees up room for cargo, equipment, or fuel. The same principle applies to other heavy industrial uses where conventional motors are limited by their sheer bulk.