NONMONOTONIC MAPS AND RELATED BIFURCATIONS IN LASER ACCELERATORS

In this paper we analyze the orbital dynamics of electrons in a laser accelerator whose high-frequency laser wave is slowly modulated both i n space and time. Slow modulations are a natural result of modulationa l instabilities and wave-particle energy exchanges, and for typical sy stem parameters we focus our study on stability and bifurcations of pe riodic orbits. It is found out that the orbital nonlinear frequencies are nonmonotonic functions of the system energy. This leads to the app earance of peculiar reconnection processes and associated inverse sadd le-node bifurcations, in addition to the more usual period doubling ca scades preceding chaos.