CST - Cannot simulate multipaction effect in cst

I'm trying to simulate the multipaction effect on a waveguide filter using CST Studio Suite PIC solver, and here is the problem: I cannot increase the power to see its result on the electron trajectory ... . I use waveguide port as a excitation and I increase the e-field but seems like it has no effect. maybe I'm wrong with the simulation procedure, can someone give a sample simulation file? or help me please?