The frequency adjustment study of standing-wave accelerating cavity of linac: calculations, simulations and measurement results

The frequency of cavities in electron linear accelerators changes because of volume variation and manufacturing error. Adjusting the frequency of cavities is one of the most important steps in a cold test, which must be considered in the design. In constructing a standing-wave tube for dual-energy linac, an aluminum tube (including two half-acceleration cavities and one coupling cavity) was constructed. In this project, to modify the changes caused by a manufacturing error, adjustment screws were used. These screws change the frequency by somewhat changing the volume of the cavities. In this paper, the calculation and simulation of frequency changes due to dimensional variation were carried out. Based on the calculation and simulation, the design of screws for a frequency adjustment in experimental conditions is done. According to the results of this paper, using the screws on the cavities wall, the resonant frequency can be changed up to 10 MHz. Therefore, using the selected method, the frequency changes caused by the manufacturing error can be compensated to the extent mentioned. In this study, the tube's resonant frequency for the π/2 mode was set equal to 2998.5 MHz, and the mechanical accuracy of the construction was obtained at 200 μm.