DESIGN AND SIMULATION OF ACCELERATING STRUCTURES FOR FUTURE LINEAR COLLIDERS

In order to obtain high luminosity and energy efficiency in future lin ear colliders, it is desirable to accelerate a train of closely spaced bunches on each rf pulse of the machine. There can be severe multibun ch beam break-up in such a collider unless some means of strongly supp ressing the transverse wakefield is incorporated into the design of th e accelerating structures. Two methods of wakefield suppression will b e discussed in this paper: (1) damping, i.e., lowering the external Q' s of the unwanted higher-order modes induced by the beam in the cells of the accelerating structures; and (2) detuning, i.e., varying the fr equencies of the higher-order modes (by varying the cell and iris radi i along the structure) so that the net induced wakefield rapidly decoh eres. The design and simulation of damped and detuned structures will be discussed. Beam dynamics simulations incorporating an accelerating structure design for the SLAG Next Linear Colider (NLC) are presented.