REVIEW OF BEAM DYNAMICS AND INSTABILITIES IN LINEAR COLLIDERS

An important issue for a next generation e+e ¡ high energy lin-ear collider is the preservation of the beam quality through the acceleration in the linac. Recent design studies at different labo-ratories adopt very flat beams at the collision point to minimize beamstrahlung. Therefore most problems are related to the ver-tical single bunch dynamics which is determined by chromatic effects in the quadrupoles and wakefield effects in the accelera-tor structures due to the misalignment or vibrations of these linac components. Almost all linear collider designs consider mul-tiple bunches in each rf pulse to raise the luminosity. The cu-mulative beam break-up instability due to long range wakefields (HOMs,higher order modes) is a severe problem for all multi-bunch schemes. Only the damping and detuning of the HOMs in the accelerator structures can reduce the long range wakefield effects. This report reviews several topics with respect to the preservation of the longitudinal and transverse beam quality in next generation linear collider designs. Single and multi bunch issues are covered