Stability of electron orbits in the strong wake fields generated by a train of fsec bunches

A tall, dielectric-lined rectangular wake field microstructure is being analyzed as a possible stageable element of an advanced linear wake field accelerator, to be driven by a train of fsec microbunches. These microbunches would be chopped out of a longer bunch using a powerful CO₂ laser and formed into a rectangular-profile bunch using a quadrupole. The fsec bunches set up a periodic wake field in the microstructure that can be built up to 600 MV/m, for example, using ten 3-fsec bunches each containing 2 pC of charge. Results are described from computations of test particle electron orbits in the longitudinal and transverse wake fields excited by these fsec bunches. It is found that test electrons in drive bunches will be well confined within the structure for a travel distance of ∼10 cm and test electrons located in an accelerated bunch will have stable motion for at least 50 cm.