Applications of superconducting technology to ISABELLE detectors

The three familiar types of magnetic-field arrangements - polar, solenoidal, and toroidal - have their advantages and disadvantages, both intrinsically for particle resolution in detectors and also from the point of view of their various technological requirements. Iron is a wonderful magnetic material apart from being limited by its saturation induction of 1.5 to 2.0 T in return yokes. Its cost per unit weight in fabricated magnets is small compared with that of other parts of the systems. Nevertheless, for the very large magnetic detectors under consideration, it will dominate costs for conventional iron-determined magnetic circuits because magnet volume and weight grow more rapidly than magnetic rigidity with increasing dimensions. In principle, the iron in a magnet yoke can be replaced by current sheets on its surface. Thus, a circular-poled iron dipole is equivalent to the fringing field in a gap left between two series-aiding solenoidal coils. Similarly, the dipole can be considered as a gap in an otherwise continuously wound toroid. This simple visualization serves to illustrate some of the contrasting features of each topology