3-D simulation of higher order modes in MILO

The C band MILO is simulated by the 3-D PIC code KARAT program in order to study the reason of frequent higher order modes in experiment and their influence on the performance of MILO. Higher order modes are caused by wave-beam action under condition of non-symmetry excitation mechanism in simulation, similar to those found in experiment. The mode of 4.01 GHz is identified and concluded as transformed through coaxial- line from the TM11 mode rising in slow-wave cavities. The other two higher order modes of 3.67 GHz and 4.53 GHz could not be concluded now.