EXAMPLES OF PHASE SLIP STRUCTURES Cd - Off To rf \ - p - GENERIC STRUCTURE TWIST

It is well known that waveguides with no perturbation6 have phase velocities greater than the velocity of light c. If the waveguide dimensions UC chceen so that the phass velocity is only moderately greater than e, only rmall perturbation6 are required. to reduce the phsse velocity to be synchronous with a high energy particle bunch. Such a lightly loaded accelerator structure will have smaller longitudinal and transverse wake per tentials and hence will lead to lower emitknce growth in an accelerated beam. Since thsse structure6 ue lightly loaded, their group velocities ue only slightly less than c and not ln the order of O.Olc, as is the csse for the standud disk-loaded structures. To ascertain that the psak and average power re quire?nents for these structure6 are not prohibitive, we examine the elastance and the Q for several traveling wave structures: phase slip structures, bellows-like structures, and lightly loaded disk-loaded structures. 2. Introduction