Design study of the superconducting magnet for a large acceptance spectrometer

New generation of experiments in Nuclear Physics is requiring large spectrometers with typical width and height at entrance /spl sim/0.36 /spl times/ 0.32 m and /spl sim/1.2 /spl times/ 0.6 m at exit and field integral /spl sim/4.8 Tm. Very low fringe field is requested, especially upstream from the beam. The innovative design of the superconducting magnet for such spectrometers has been extensively studied on the base of active shielding method. The designed magnet is the combination of several tilted and graded racetrack-type trapezoidal windings for creating both main and shielding fields. This requires high mechanical rigidity by use of aluminum containers where windings will be encased. Indirect cooling with thermosiphon is suggested. The internal protection method is discussed. In the paper the details of the magnet design, magnetic field shape, cooling and protection are presented.