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Challenges

The R&D process for magnets is like feeling one's way forward in a huge maze. Just like rocket launch doesn't allow real-world simulation in advance, the magnet can't be tested before execution or be repaired after failure. One failed trial will cost nearly RMB 1 million (over $150,000). Without a narrow trial-and-error strategy in advance, all resources could be used up in one fell swoop.

It's necessary to be very careful for every step. The superconducting wire that is tens of kilometers in the magnet is placed in -269℃ ultra-low temperature liquid helium, and the maximum force of the coil after power is on may exceed 1,000 tons, which is equivalent to the force produced by 10,000 horses running in one direction at the same time. Under the huge force and low temperature, all materials would have reached their limits. At that point, even if energy reaches the coil that's as small as the energy produced by a peanut slipping from the hand to the ground, it will cause the magnet to quench, instantly releasing several tens of thousands of volts of high voltage, and therefore huge energy. Any carelessness will pose a huge risk of partial burnout and complete failure.

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Solution

United Imaging Healthcare has created a rigorous and efficient innovation model in response to this dilemma: 30,000 hours of in-depth exploration of only one technical point. Engineers carried out a large number of joint designs of electromagnetic field and stress, seeking the balance point of electromagnetic field and stress in a small space, and selected aerospace-grade unique materials from the physical properties at extremely low temperatures. They conducted a large number of analyses and tests to avoid potential risks.

All those efforts were not in vain. In January 2014, in United Imaging Healthcare's 3.0T magnet workshop, the magnet reached an ultra-high field strength of 3.0 Tesla, marking the moment China had broken the standard in independently developed 3.0T magnet. Since then, our MRI systems equipped with the 3.0T superconducting magnet independently developed by United Imaging Healthcare have successively entered China's top 3A hospitals. The 3T MRI equipment is also available overseas. In October 2019, United Imaging Healthcare successfully developed the world's first large aperture 3.0T net magnet, with an unprecedented wide bore of 75 cm for patients. In June 2020, the world's first 5.0T magnet and China's first 9.4T magnet were successfully born at United Imaging Healthcare.

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The Process of Forging a Superconducting Magnet
The "Heart" of MRI
Magnetic field is something we can't capture physically but it is everywhere around us. It is a mystery leading to the nature of life.
Superconducting Wires Requires Fine Craftsmanship
The heart's meridians: superconducting wires less than 3 mm in diameter and 80 to 100 kilometers in length. Winding it on a special coil support in a specific way, the speed, gap, relaxation, flatness, all test the craftsman's skills, if it is missed by the slightest, it will be a thousand miles away.
Connecting Coils in Precise Way
The wound and cured coils are connected end to end. The more than 30 niobium-titanium filaments with a diameter of only 20 microns hidden in the superconducting wire are separated and precisely butted. A slight difference will seriously affect the superconductivity of the magnet.
Great Leakproofness
The connected coil is placed in the liquid helium tank to seal, and the aluminum foil used in the aerospace field, the force balance seal suspension design will withstand the temperature difference of nearly 300 degrees inside and outside the tank, ensuring zero volatilization of liquid helium.
Tolerate in Extreme Weather
Vacuuming, pre-cooling, and injecting liquid helium at minus 269 degrees Celsius, the constant ultra-low temperature will ensure that the resistance of the superconducting wire is zero, the current will run continuously, and the magnetic field will exist forever.
A Perfect Superconducting Magnet Final Journey
When the electricity turns on, the intensity continues to increase, and the magnetic field is generated. As the field intensity climbs, the current finally reaches the ideal power, and the magnetic field is captured in a stable attitude, we eventually get a perfect superconducting magnet.