Preliminary Modeling and Simulation Results of a Megawatt HOM-IOT

Summary form only given. The high order mode inductive output tube (HOM IOT) is enabling technology for the Navy's MW-class FEL due to its high efficiency, compactness, low cathode voltage and standby characteristics. The only HOM IOT ever built is CPFs VHP-8330A1 prototype. It was developed for the APT program; unfortunately APT was cancelled in favor of reactor-based technology. The prototype achieved 920 kW of power when operated in pulse mode; unfortunately testing both long pulse and continuous wave was not possible due to problems associated with deformation of the annular control-grid. Recent advances in multiple beam klystron (MBK) electron optics technology have taken place which allows us to remove the problematic annular control-grid and cathode segments used on the VKP-8330A prototype and replace them with multiple, conventional IOT spherical control-grids and cathodes. We examine the effect of this change on performance and determine the number of electron beams a given design [frequency] can accommodate. Preliminary modeling and simulation results of a HOM IOT operating at 500 MHz, 625 MHz and 750 MHz isshown. We also provide maximum output power levels, size, and weight estimates for tubes designed to operate at each of the above frequencies