1. Design and Optimization of Force-Reduced Superconducting Magnets
Szabolcs Rembeczki*
74th Annual Meeting of  Southeastern Section of the American Physical Society (SESAPS) November 8-10, 2007 Nashville, Tennessee
*Florida Institute of Technology,
Dept. of Physics and Space Sciences,
Melbourne, Florida

2. Why High Magnetic Fields ?
Reaching higher magnetic fields would open new areas in various fields of research.
Applications in:
Condensed matter physics
High energy physics
Spin physics
Materials chemistry
Structural biology
Power industry etc.
Several targets for magnet technology:
30 T Superconducting high resolution NMR
60 T DC Hybrid magnet
100 T Long-pulse magnet
Great demand on higher
magnetic fields !
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SESAPS

3. Current High Field Magnet Technology
45 T Hybrid Magnet at NHMFL
Hybrid concept:
Resistive insert Superconducting outsert
Layered structure
Normal Conducting
Water cooled
Superconducting
Liquid Helium cooled
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4. Operational Parameter Technical Superconductor
Superconducting Materials
Operational Parameter
Technical Superconductor
NbTi
(ductile)
Nb3Sn
(brittle)
HTS
Toper(K)
4.2
20-77
Boper(T)
< 10
< 25
>100
Promising HTS Materials:
MgB2
Bi2212
YBCO
Superconductors are pressure and strain sensitive !
H.J Schneider-Muntau et al.: Magnet Technology Beyond 50 T, Trans. Appl. Supercond., Vol.16, 2006
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SESAPS

5. Issue of Lorentz Forces in High Magnetic Field Magnets
High Field Magnets
High Stored Energy in the Magnet
Large Lorentz Forces
The main challenge of high field magnet development is the handling of the Lorentz forces.
The pressure due to Lorentz force in a thin winding cylinder:
Pm = Em = B2 / 2μ0
(Em – energy density)
For B = 50 T field: Pm = 1 GPa
(Yield tensile strength of maraging steel ~ MPa )
Lorentz force acting on SC coils: movement of the coil configuration can generate local frictional heat resulting in quench !
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SESAPS

6. Force-Free Magnetic Field
A magnetic field configuration
B is force-free in a
region if the j current(density) and B are parallel:
FL = i l × B = 0
and
j × B = 0
(G.J. Buck, Journal of Applied Physics, Vol.36.)
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7. Force-Reduced Superconducting Magnet
Method of Force Reduction:
solenoid & toroid with windings of variably directed currents in N layers
geometrical parameters, conductor materials, and operational parameters
needs to be optimized
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8. Concluding Remarks
State-of-the art high temperature superconductors allow realization of magnetic fields in access of 50 Tesla
However, the current carrying capacity of these conductors is compromised by stress and strain dependence of the materials
Reducing the forces acting in the winding configurations of high field magnets enables the application of such conductors
The main challenge of high field magnet development is the handling of the Lorentz forces
Force reduction is necessary in order to reach highest magnetic fields and to reduce the mass of the magnet support structure
Force-reduced coils are the enabling technology for highest magnetic fields needed for basic research and applications !
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SESAPS

9. Questions or Comments? Thank You!
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