Thoughts about Gantries

The section 2007 FFAG gantry reviews an FFAG gantry, which transport beams with momenta varying by about a factor of two at constant excitation, well matched to FFAG accelerators. The section FODO gantry describes pulsed gantries with magnet excitation proportional to the beam momentum, and a small difference between beam and design momentum. They are well matched to pulsed synchrotrons. The dispersion in the bending plane need not be controlled as tightly as in the FFAG gantries. Nearly round beams are obtained in the tumor at the rotation axis by operating with much smaller phase advances in the plane perpendicular to the median plane. Scanning, installed between the end of the gantry lattice and the rotation axis, is briefly discussed in the section Scanning.