A gantry is provided for focusing beams of charged particles having differing momentum to charge ratios to a substantially common point. The gantry comprises at least one toroidal magnet having a central bore and a primary axis extending along the central bore and configured to receive beams of charged particles at different radial locations dependent on the momentum to charge ratio of the beam. The toroidal magnet comprises a plurality of discrete, substantially planar coils spaced apart and extending radially from the primary axis and configured to produce a magnetic field that is periodically symmetric about the primary axis.