Beam dynamics design and simulation studies of the APT superconducting linac

Our design approach takes advantage of the large velocity acceptance of the superconducting cavities. As a guide to an initial layout, an analytic model of multi-cell cavities excited in a n-mode was used to provide an expression for the transit-time factor as a function of particle velocity. A simple cavity-field distribution was assumed where the fields are uniform in the accelerating gaps and zero immediately outside the gaps. For APT the RF power delivered to the beam greatly exceeds the power dissipated in the superconducting walls. Then, the RF power required per cavity is approximately equal to the beam power, which is given as the product of the beam current times the particle energy gain per cavity