Design and Optimization of a Multi-Aperture Rebuncher Model Cavity for High Current Neutron Sources

Path modulation is an effective method for increasing the peak beam current. To maintain the longitudinal structure of the compressed beam, a multi-aperture focusing chamber capable of simultaneously focusing multiple beam bunches must be placed at the symmetrical point of the beam compression system. This paper presents a geometrically heterogeneous design based on a conventional QWR chamber and performs analytical calculations using coaxial line theory and modified formulas. By adjusting certain geometric parameters of the chamber, the voltage deviation in the accelerating gap is controlled within 1%. Simulation software was used to perform parameter sweeps for electromagnetic design optimization, and the high-frequency parameters of the cavity were calculated for both the empty cavity and configurations with tuners of different radii. The results indicate that the cavity operates at a frequency of 81.25 MHz, with a branch impedance of 5.62 MΩ, a Q-factor of 14,734.2, a power dissipation of 1.78 kW, and a Kilpatrick factor of 0.51. Simulation results of the beam dynamics using the PIC program show that the cavity exhibits significant beam focusing with no beam loss; the presence of errors such as transverse field and beam phase jitter has no significant effect on the beam compression performance.