Design and Fabrication of Side-Coupled RF Cavity for S-band 6/3 MeV Dual-Energy Electron Linac

We demonstrate the design and manufacture of RF (radio-frequency) electron linac (linear accelerator) cavity of 6/3 MeV dual-energy X-ray generator for air-cargo security inspections. When an accelerated electron beam collides with the metal target, an X-ray is generated by a bremsstrahlung process. We designed a dual-energy RF cavity using a three-dimensional electromagnetic field simulation code and an electron beam trajectory code. The designed RF cavity is a side-coupled standing-wave type, driven by the π/2 mode, and has a resonant frequency of 2856 MHz. The maximum dose rate of X-ray was calculated to be 7.07 and 0.91 Gy/min at 1 m for an X-ray energy of 6 and 3 MeV using a tungsten target, respectively. In the simulation results, the accelerating gradient was about 13.5 MV/m, the Q-factor was 15,900, and the total length of the RF cavity was 57 cm for 6 MeV of the maximum accelerated electron energy. The resonance frequency and the Q-factor of the fabricated RF cavity were measured by 2855.34 MHz and 14,000, respectively.