RF characteristics of multiple-gap resonant cavity for sheet beam extended interaction klystron

The sheet beam extended interaction klystron (SBEIK) has the typical and attractive characteristics with the plan structural multiple-gap cavity and extended beam-wave interaction system. A type of novel miniaturization strong-coupling five-gap extended resonant cavity was investigated combined with the design of W-band SBEIK, which was compared with the traditional weak-coupling five-gap resonant and output cavity. The obtained characteristics shows that the strong-coupling five-gap cavity may have many advantages of resonant mode separation, radio frequency (RF) fields coupling in the gap and RF energy exporting, etc. Then, the degeneracy mode competition for the strong-coupling five-gap cavity was studied due to its axial period structures. The result shows that the frequency interval between the work mode and vicinal non-working mode is above 600 MHz, which is higher enough than the required 100 MHz bandwidth for the SBEIK. Finally, the 3D particle in cell (PIC) simulation software was used to calculate the beam-wave interaction for the strong-coupling five-gap extended output cavity, the expected high output power was observed with the corresponding performance and favorable stability. Thus, the research is very important for the physical design and engineering development of the SBEIK in the millimeter-wave and terahertz band with high power output radiation later.