Magnets for high energy colliders

The problem of producing, preserving and stably colliding low emittance bunches for long periods of time is a formidable problem involving questions of jitter, dynamic alignment and reproducibility associated with magnetic and mechanically hysteresis. Permanent magnets provide ideal solutions for lower capital and operating costs. Because they are light in weight, compact and require no power or cooling they are easy to use, stable and uniquely reliable. With their low permeability this implies a minimal impact on the surrounding environment and vice versa. For example, they are ideal for final focus systems embedded in particle detectors with strong solenoidal fields while their strength and compactness minimizes the solid angle they subtend around the interaction point (IP) as well as their target thickness along the beam line. We discuss calculations there /rvec B/ is a nonlinear, anisotropic function of /rvec H/. The results explain discrepancies observed measurement and calculation of permanent magnet systems and indicate good multipoles are possible with far higher strengths than previously obtained. We extend previous calculations on the obtainable gradients for different types of quadrupoles down to 1 mm bore radii where 2000 T/m appears possible with conventional designs and available materials. We discuss why much higher gradients are possible by the same means. Additional specifications for PM manufacturers are recommended. 14 refs., 5 figs