Design of a superferric quadrupole magnet with a high field gradient

FAIR, a new international accelerator complex is' now being developed by GSI (Darmstadt, Germany). The synchrotron SIS100 is a part of this complex and will be equipped exclusively with fast-cycling superferric magnets. The magnet system of this accelerator includes 168 identical quadrupoles with a maximum gradient of 33.4 T/m in an elliptical useable aperture of 120 min x 65 mm. An important requirement of the quadrupole design is a field gradient uniformity better than +/- 0.06% for field gradient variation range of 3 T/m-3.3 T/m. This goal is achieved by introducing slots in the central part of the magnet poles, creating the effect of artificial saturation. Simultaneously, these slots reduce the eddy currents in the yoke, induced. by the current ramp in. the magnet coil. This is important because the whole magnet will be operated near 4.2 K, so the power loss in the yoke should be minimized. Additionally, the shape of the quadrupole pole ends was optimized to provide the necessary integral field quality.