Hot test of gyrotron cavity interaction using a 3D CFDTD PIC method

Modeling a gyrotron cavity interaction in 3D and time-domain is very challenging due to the open-end features of cavity structure and higher-order mode excitation employed to achieve high efficiency. In this work, a 3D conformal finite-difference time-domain (CFDTD) particle-in-cell (PIC) method has been developed to perform a hot test of gyrotron cavity interaction. With a tailored gyrobeam emission, not only forward wave but also backward wave interactions have been observed in an MIT gyrotron cavity, consistent with a recent experiment at MIT. Our preliminary results show that the 3D CFDTD PIC method could provide an alternative modeling tool for studying the gyrotron cavity interaction for further improving efficiency and studying mode competition.