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October 14, 2009

High Field Superconducting Magnets and Applications


Superpower Inc a subsidiary of Philips talked about a potential 70 Tesla Superconducting magnet based on REBCO. they built a 26.5 Tesla magnet but the REBCO has 70 Tesla critical field. (17 page pdf)

Aug 2009 Superpower presentation indicates a 33.8 Tesla superconducting magnet was created and 35 Tesla is "within their grasp"

REBCO: melt-processed REBa2Cu3O7−δ (RE: rare earth, REBCO) superconductors can be magnetized to a strong bulk magnet and have high critical current density JC.

Superconducting magnets have been an enabling technology for magnetic resonance imaging (MRI), particle accelerators and colliders and play an essential role in fusion devices
•The development of high magnetic field superconducting solenoidshas been increasing the sensitivity and resolution of nuclear magnetic resonance (NMR) and opening opportunities for advancements in condensed mater physics, biology, chemistry, material sciences, physiology and psychology
•Superconducting magnets have some advantages over resistive electromagnets:
–The field is generally more stable, resulting in less noisy measurements
–They can be smaller

The applicability of a superconducting wire for a high field magnet is mainly determined by
–superconducting property Je(B) = Ic(B)/Ae
–mechanical properties
–lengths of the wire

Improved in-magnetic-field performance
•Approaches to higher Ic(B):
–The composition or the ratios of RE to Baand RE to Cu is the key to achieving high Ic
–Substituting rare-earth in superconductor composition, such as Smand Gd, for Y in the YBCO film has been proved to be effective in improving in-magnetic-field properties
–Zr additions in REBCO films were shown to be effective pinning centers








University of Mississippi had a talk which projected 45 Tesla BSCCO solenoids near term and 50 Tesla solenoid potential.

5 pages on superconductor magnets used in VASIMR plasma propulsion rocket (2005 paper)



Space superconductors are critical to the development of a high power plasma rocket such as VASIMR. Their use is also natural in addressing the radiation problem that threatens astronauts in long space missions.

The choice for VASIMR has been the high temperature superconducting compound Bismuth
Strontium Calcium Copper Oxide (BSCCO;) however, more recently, the less expensive and easily manufactured Magnesium diboride (MgB2) is providing intriguing possibilities currently under study.

The first prototype BSCCO magnet was an 8 superconducting pancake set, assembled under an axial compression load. With approximately 500 turns and a current of about 110 amps, it produced a field on axis of about .3 Tesla. The unit was cooled to about 800K with an industrial, low power cryocooler.

While testing with BSCCO continues, new superconducting wire is also being developed by investigators from the Texas Center for Superconductivity and Advanced Materials (TCSAM) at the University of Houston. This material is based on Magnesium diboride (MgB2) superconductor, which has a lower (20-250K) operating temperature than BSCCO. Operation at this temperature may be feasible with liquid hydrogen or deuterium propellant in a regenerative mode. The use of MgB2 is attractive as the critical field is significantly higher (up to 7 Tesla) and the conductor is also lighter and less expensive.




In July 2009, the 200 KW VASIMR powered up a 2 Tesla superconducting magnet for its plasma engine.

FURTHER READING
There were proposals for 50-60 Tesla high temperature superconducting solenoids for working with muons.

Superconducting bulk magnet for maglev vehicle: Stable levitation performance above permanent magnet guideway (2008)

High-temperature superconducting (HTS) maglev vehicle is well known as one of the most potential applications of bulk high-temperature superconductors (HTSCs) in transported levitation system. Many efforts have promoted the practice of the HTS maglev vehicle in people's life by enhancing the load capability and stability. Besides improving the material performance of bulk HTSC and optimizing permanent magnet guideway (PMG), magnetization method of bulk HTSC is also very effective for more stable levitation. Up to now, applied onboard bulk HTSCs are directly magnetized by field cooling above the PMG for the present HTS maglev test vehicles or prototypes in China, Germany, Russia, Brazil, and Japan. By the direct-field-cooling-magnetization (DFCM) over PMG, maglev performances of the bulk HTSCs are mainly depended on the PMG's magnetic field. However, introducing HTS bulk magnet into the HTS maglev system breaks this dependence, which is magnetized by other non-PMG magnetic field. The feasibility of this HTS bulk magnet for maglev vehicle is investigated in the paper. The HTS bulk magnet is field-cooling magnetized by a Field Control Electromagnets Workbench (FCEW), which produces a constant magnetic field up to 1 T. The levitation and guidance forces of the HTS bulk magnet over PMG with different trapped flux at 15 mm working height (WH) were measured and compared with that by DFCM in the same applied PMG magnetic field at optimal field-cooling height (FCH) 30 mm, WH 15 mm. It is found that HTS bulk magnet can also realize a stable levitation above PMG. The trapped flux of HTS bulk magnet is easily controllable by the charging current of FCEW, which implies the maglev performances of HTS bulk magnet above PMG will be adjustable according to the practical requirement. The more trapped flux HTS bulk magnet will lead to bigger guidance force and smaller repulsion levitation force above PMG. In the case of saturated trapped flux for experimental HTS bulk magnet, it is not effective to improve its maglev performances by increasing of charging magnetic field, when the guidance force at WH 15 mm is 5.7 times larger than that by DFCM of FCH 30 mm. So introducing HTS bulk magnet into the present maglev system is feasible and more controllable to realize stable levitation above applied PMG, which is an important alternative for the present HTS maglev vehicle.


78 page presentation on using superconducting magnets for conventional tokomak fusion projects. Reviews HTS superconductors and what can be achieved with them. The magnets would be good for any other application as well. The tokomak projects get the best magnets and are pushing the tech envelop.

August 2009, 40 page presentation by LLNL and Superpower on superconductors.

The 2g Superconductor program has a direct impact on OE sub program goals namely, development of prototype wire achieving 1,000,000 A-m and production of HTS coil operating in applied magnetic fields up to 5 T at 65 K


Superpower technical documents.

The magnet lab in August 2009 described the rapid progress over the last two years in high field superconducting magnets.

In just two years, the National High Magnetic Field Laboratory and SuperPower have made great strides in improving the performance of the material for applications that range from electric utility transmission to high-field magnets.

"High-temperature superconductors have shown rapid progress, especially YBCO conductors, and 30 tesla, while challenging, is still far away from any fundamental limit," said Huub Weijers, who oversees coil testing at the Mag Lab. "With continued R&D, even stronger all-superconducting magnets are possible."



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