Implications of the Low Field Levels in the LEP Magnets

For the C-shaped laminated magnet cores, which have been adopted in the recent versions of LEP, advantage has been taken of the required low field levels to reduce the filling factor to less than one third. This both improves the performance and considerably reduces the price of the magnets. Starting from magnetic measurements on different steels, and by using a semi-quantitative model, it is shown that a satisfactory field uniformity can be maintained at an injection field of 0.017 T with a medium grade, low carbon steel, owing to the mutual compensation between the reduction in permeability with field level and the effect of coercivity. A novel method is being developed for fabricating these magnets using a cement mortar to fill the interlamination spaces and bind the laminations together. A 60 cm long, ¿-scale model has produced excellent mechanical and magnetic results.