Lattice design of the 144 MeV induction microtron for C-60

A recently proposed racetrack-shape fixed field induction accelerator has been more specifically refined as the 144 MeV Induction Microtron for C-60. Two approaches of tracking simulation taking 3D magnetic fields of a 90 degree bending magnet into account and linear optics calculation have been developed for refining design. It turned out that an inherent feature originated from a finite magnet length and the incidence/exit angle of 45 degree produces a kind of systematic closed orbit distortion depending on particle energy. Orbit stability in the horizontal direction can be achieved by introducing steering magnets or improving the magnetic field homogeneity in the Z direction. Dispersion function of another important lattice function is analytically evaluated and compared with the result obtained through the 3D beam tracking. (author)