Numerical study of the start-up scenario of a 670 GHz gyrotron operation at TE31,8 mode

Summary form only given. In order to develop a system to detect concealed radioactive materials, we are designing a 670 GHz gyrotron with enough power to cause breakdown in the air 1 . Design studies of the cavity and the magnetron injection gun (MIG) of this gyrotron had already been presented. Presently we are studying the simple start-up regime for this 670GHz gyrotron operating at TE318 mode. Stable operation at this mode was verified in experiments with a 170 GHz, 1 MW gyrotron . For such a high-order mode, it is important to study the excitation condition of different modes inside the cavity during the voltage rise phase, and how to avoid excitations of dangerous parasitic modes. Using available MIG data, we plan to perform numerical simulation using MAGY . The results of these simulations will be illustrative for our future experiments, and the results of the study will be presented at the conference.