Damped accelerator structures for future linear e± colliders

Preliminary work on accelerator structures for future teraelectronvolt linear colliders which use trains of e^± bunches to reach the required luminosity is described. These bunch trains, if not perfectly aligned with respect to the accelerator axis, induce transverse wakefield modes into the structure. Unless they are sufficiently damped, these modes cause cumulative beam deflections and emittance growth. The envisaged structures are disk-loaded waveguides in which the disks are slotted radially into quadrants. Wakefield energy is coupled via the slots and double-ridged waveguides into a lossy region which is external to the accelerator structure. The requirement is that the Q of the HEM₁₁ mode be reduced to a value of less than 30. The work done so far includes MAFIA code computations and low-power RF measurements to study the fields