The stochastic behavior of electrons in free electron lasers with variable parameter wigglers

In this article, the motion of electrons in free electron lasers with variable parameter wigglers is discussed. It is pointed out that, the more quickly the parameter varies, the more trapped electrons move stochastically. The influences of such stochastic motion on laser efficiency have been analyzed numerically. A statistical method to describe the beam behavior in strong stochastic limit has also been developed.