the start up and linear growth process of the microwave within the foldaway-concentric cylindrical resonant cavity are analyzed based on the one dimensional model firstly, then a 2.5-d pic code is employed to study the nonlinear interaction 由于电子束在同一个腔内受到了100深度的调制,可以直接加微波提取腔进行微波提取。然后用二维半pic程序对它进行数值模拟研究。