Generation of very high continuous fields by polyhelix and polyhelix hybrid magnets

Abstract

Polyhelix magnets have many advantages over Bitter magnets: they withstand higher Lorentz forces, supporthigher power densities and allow for more efficient radial current density distributions. As a result they can be more compact and generate higher fields. We describe the concepts and construction techniques we used to built a version of this new type of high-field magnet, which has recently generated, with a power of 10 MW and in a room temperature bore of 50 mm diameter, the record field of 25 T. Still higher continuous fields can be generated using hybrid magnets, i.e. by surrounding the resistive magnet with a superconducting magnet which provides a booster field of up to 13 T. Since polyhelix magnets are compact, they are also well suited for hybrid magnets. We give a short description of the Grenoble polyhelix hybrid magnet, which is to generate 30 T in a 50 mm room temperature bore. Calculations indicate that using the same technology continuous magnetic fields up to 40 T appear to be possible.