Magnets for high energy colliders

The strengths of conventional quadrupole designs based on coil, steel, and PM (permanent magnet) dominated systems are compared. In each case, detailed 2-D calculations were made for a range of radii consistent with known constraints. The results yield a straightforward comparison of the limiting gradients achievable as a function of radius and thus provide useful guidelines for various magnetooptical calculations as well as benchmarks for magnet designers, including those interested in alternative approaches. Previous calculations on the obtainable gradients for different types of quadrupoles are extended down to 1-mm bore radii where 2000 T/m appears possible with conventional designs and available materials. Why much higher gradients are possible by the same means is discussed. Additional specifications for PM manufacturers are recommended