APPLICATIONS OF TECHNOLOGY:
- Ion-beam cancer therapy gantries
- Superconducting magnets
- High energy physics
- Simpler, more cost effective mandrel construction
- Reduces field ramping and eddy currents
- Enables piecewise construction using small laminations
A Berkeley Lab team of engineers led by Shlomo Caspi has invented a technology to construct a curved superconducting magnet capable of bending an ion beam 90° in a cancer therapy gantry, where it can be precisely aimed at tumors. (See Compact Toroidal Magnet for Carbon Ion-beam Therapy, IB-3054, for more details on the superconducting toroid magnet itself.) Critical to the design is an innovative method of constructing a curved tube, or mandrel, that has a precise pattern of grooves on its exterior. The computer-designed pattern of grooves serves as a template to guide electric wires as they are wound around the mandrel to build the magnet, which would operate as a highly efficient superconducting magnet when chilled to near absolute zero (4.5K).
The Berkeley Lab team discovered that the optimal method of fabricating the complex mandrel is to assemble it from a succession of thin rings, or vertical slices, which when fully laminated form a pipe that curves 90°. The piecewise construction using a laminated approach opens up the design to a greater number of manufacturing techniques and materials choices to reduce cost. Sectioning the mandrel reduces eddy currents produced during field changes accommodating the scan of beam energies during treatment.
The symmetrical geometry of this grooved toroid dictates that nearly the entire curved structure can be fabricated from dozens of identically shaped rings. Each ring — a vertical slice of the curving pipe — has exactly the same pattern of notches on its outer edge. The slices and notches are slightly canted, however, so instead of forming a corduroy of straight grooves on a straight pipe as they are laminated, they form instead a curved pipe with grooves on the surface that twirl around the mandrel in the prescribed fashion. These grooves (azimuthally separated by ribs and radially connected to a spar) assure that the electromagnet wires are properly positioned as they are spun around the pipe and are sufficiently stiff to resist Lorentz forces from accumulating during operation.
DEVELOPMENT STAGE: Modeled concept
STATUS: Patent pending. Available for licensing or collaborative research.
FOR MORE INFORMATION:
Caspi, S., Arbelaez, D., Brouwer, L., Dietderich, D.R., Felice, H., Hafalia, R., Prestemon, S., Robin, D., Sun, C., Wan, W. “A superconducting magnet mandrel with minimum symmetry laminations for proton therapy,” Nuclear Instruments and Methods in Physics Research AVol. 719, pp. 44-49, April 2013.
REFERENCE NUMBER: IB-2013-021