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

In this paper, we reported on the design of a 10 MW, 1300 MHz multiple beam klystron for TESLA superconducting linear accelerator. The multiple beam klystron is used in the accelerator because of its ability to produce high RF output power at moderate electron beam energies. The beam optics design has been verified by fully 3D simulations using the codes Michelle and Mafia. Electron trajectories in the gun region as calculated from Mafia codes.

A high-efficiency, Multiple-Beam Klystron (MBK), designated the VKL-8301, is being manufactured for the DESY Tera Electron volt Superconducting Linear Accelerator (TESLA) in Hamburg, Germany. There are a number of excellent reasons for using an MBK for this application. The primary reasons are reduced size and lower operating voltage with respect to the conventional, single beam counterparts. Once this decision has been made, the class of MBK must now be selected. MBKs can be divided into two categories: Fundamental Mode (FM) and Higher-order Mode (HM) devices, distinguished by the interaction mode of the cavity resonators. Each class has inherent advantages and disadvantages dependent upon end-user requirements. For the 10 MW, 1.3 GHz TESLA application the HM-MBK is the clear choice. The primary factor influencing this choice was operational life, since the accelerator will require approximately 600 MBKs. The advantage of the HM approach is low cathode loading. Our cathode loading design goal of 2 A/cm/sup 2/ or less has been achieved. For this application the HM-MBK cathode loading is a factor of four lower than competing FM-MBK designs and a factor of three lower than the SLAC 5045 design. The VKL-8301 will use six off-axis electron beams interacting with a combination of TM/sub 010/ and hybrid TM/sub 020/ cavities. These six beams are equally spaced on a diameter of approximately 25 centimeters. Because of the large beam-to-beam separation, individual high-area convergence guns can be utilized versus the single multi-emission-site gun used in FM-MBK's. This solution requires a sophisticated focusing system that is relatively difficult to realize, compounded by our use of confined-flow focusing. Newly developed, state-of-the-art three- dimensional electromagnetics codes have been used to design the novel electron-beam-focusing system and microwave cavity geometry. Modeling and simulation results will be presented, hardware will be shown, and a description of the FM- versus HM-MBK selection process will be discussed.

Summary form only given, as follows. Progress to date is reported on the development of a 10 MW, 1300 MHz multiple beam klystron for the TESLA superconducting linear accelerator. A multiple beam klystron will be used because of its ability to produce high rf output powers A moderate electron beam energies. In this device, low cathode current density loading and hence longer cathode life is achieved by the use of off-axis electron beams. Beam bunching occurs in a series of separate fundamental mode klystron cavities whereas drive power input and output power extraction occur in large over-moded cavities for power combination reasons. The essential parameters of the device are 114 kV beam energy, 131 A beam current (21.8 A per beam), 65% efficiency, 50 dB gain and 150 kW of average rf output power.