The strongest superconducting user magnet in the world currently has a field strength of 23.5 tesla. When this ambitious project is completed in 2017, the strongest superconducting magnet on the planet will be housed at the MagLab. At 32 tesla, it will be a whopping 8.5 tesla stronger than the current record – a giant leap in a technology that, since the 1960s, has seen only baby steps of 0.5 to 1 tesla. In June 2015, a test for the 32 tesla magnet set a new world record of 27 teslas for an all-superconducting magnet.
Among other innovations, it combines low-temperature superconductors commonly used in today’s superconducting magnets – niobium tin and niobium titanium — with “YBCO,” a superconducting ceramic composed of yttrium, barium, copper and oxygen. Although YBCO-coated conductors in this case operate at the same temperature and in the same helium bath as their metallic counterparts, they remain superconducting far above the practical magnetic field limits inherent to niobium-based superconductors. For this reason, YBCO can also be called a high-field superconductor; it superconducts at far higher temperatures than niobium-based materials but, like all superconductors, performs best at very low temperatures.
The 32 tesla will be the first high-field magnet available to researchers to incorporate YBCO, a finicky material a few commercial companies have been developing for years in collaboration with MagLab engineers and scientists. The finished, 2.3-ton magnet system will feature about 6 miles of YBCO tape, formed into 112 disc-shaped “pancakes.” Two inner coils of YBCO, fabricated at the MagLab will be surrounded by a commercial outsert consisting of three coils of niobium-tin and two coils of niobium-titanium.
The new magnet will particularly be more attractive for users whose experiments require lower noise and longer running times than the resistive magnets can offer, while the relatively fast ramp-rate of 32 T/hour in this superconducting magnet also allow for many field sweeps per day.
36 Tesla Hybrid Magnet
On Nov 8, 2016, after a decade of planning, designing and building, the National MagLab has successfully tested the latest addition to its world-record lineup: a 33-ton engineering marvel called the series connected hybrid (SCH) magnet. The instrument reached its full field, 36 tesla (tesla is a unit of magnetic field strength; a strong refrigerator magnet is .01 tesla, and a typical MRI machine is 1.5 to 3 tesla).
The SCH is not the strongest continuous-field magnet in the world — that honor goes to the MagLab’s 45-tesla hybrid magnet, which has held the record since 1999. It is, however, expected to become the strongest magnet in the world by far for nuclear magnetic resonance (NMR) spectroscopy, a powerful technique used by biologists and chemists to study molecular structures in proteins and materials.
What makes the SCH unique is that it can create a very high magnetic field that is also of very high quality. For magnets, “quality” means a field that remains constant over both the time it takes to run an experiment and the space in which the experiment takes place in the magnet. Unlike most of the physics research done in magnets, NMR requires fields that are very stable and homogeneous.
At 36 tesla, the SCH is more than 40 percent stronger than the previous world-record NMR magnet (the MagLab’s Keck magnet and more than 50 percent more powerful than the highest field high-resolution NMR magnet, a 23.5 tesla system in Lyon, France.
In NMR, scientists use magnets and radio waves to locate a specific element (commonly hydrogen) in proteins and other samples, which helps them figure out those complex structures. A powerful technique in health research, scientists use it, for example, to pinpoint a virus’ vulnerability to drugs.
Existing NMR magnets are limited to locating just a handful of elements, notably hydrogen, carbon and nitrogen. The SCH’s 36-tesla field could revolutionize NMR because it significantly boosts the instrument’s sensitivity, expanding the menu of elements scientists can see.
“There’s going to be a real increase in the reach of NMR into the periodic table,” said Tim Cross, who oversees NMR research at the MagLab’s Tallahassee headquarters. “So we’re going to be able to look at many more elements than we’ve really been able to in the past.”
Zinc, copper, aluminum, nickel and gadolinium — all of interest for battery and other materials research — will now be observable using the SCH. But for most biologists, the real prize will be oxygen.
“Oxygen is where so much biological chemistry takes place,” said Cross, “and until the SCH, we’ve just not been able to look at it.”
The new magnet will also allow researchers to vary the field strength and switch relatively easily from examining one element in a sample to another, which will help them to collect more and better data.
The SCH is also extraordinary for the size of its bore — that space in the middle of the cylinder where the experiment goes. As an engineering rule, the stronger you make a magnet, the narrower that bore needs to be: It’s just really hard to make a high-field magnet with lots of room in the middle. Yet in the SCH, the MagLab has achieved exactly that. The bore needed to be 40 mm wide (compared to the 32-mm-wide bore of the 45-tesla hybrid) because NMR experiments require sending a lot of instrumentation into the bore with the experiment.
Now that the SCH has passed its big test, scientists and engineers will spend about a year completing and testing the customized instrumentation required for NMR experiments in the SCH (funded with a separate $1.3 million NSF grant). The magnet is expected to be available for physics experiments in early 2017.
Commercial 18 Tesla Teslatron
Oxford Instruments sells an integrated cryogen free magnet and variable temperature insert, TeslatronPT – up to 18 Tesla, 1.5 K – 300 K
Cryogen free superconducting magnet system providing top loading access to a sample in a variable magnetic field / low temperature environment.
Standard magnetic fields up to 18 Tesla in a compact geometry
Other magnet geometries available including split pairs, vector rotate magnets, etc.
No cryogens needed, just electricity supply
The Oxford Instrument product range now includes:
High field wide bore research magnets
– 19 Tesla / 150 mm bore
– 15 Tesla /250 mm bore
Solenoid superconducting magnets up to 22 Tesla
Cryofree magnets up to 18 Tesla
Split pair superconducting magnets, typically up to 15 Tesla
Vector rotate magnets
Highly challenging custom designed superconducting magnets to suit specific applications
Integrated high field magnet with ultra low temperature fridge (up to 18 Tesla)
SOURCES – National Magnet Lab, Oxford Instruments