Measurement of Characteristic of X-band RF Cavity for 6 MeV Electron Linac

A compact 6 MeV electron linear accelerator (linac), intended to be used as an X-ray source for a dual-head gantry radiotherapy system has been developed. In order to meet the size requirements of the dual-head gantry machine, an X-band radio frequency (RF) technology is used, which facilitates a reduction in the size of the linac, which is nine times smaller than the conventional medical purpose linac using S-band RF technology. Nevertheless, the X-band RF technology requires much higher machining precision and higher-quality surface finish owing to the electrical breakdown phenomena resulting from its small size. After the design was completed, the RF cavity was machined using high-precision machining technology, achieving machining tolerances of ±2 μm, and a surface roughness less than 50 nm. Various RF properties were measured in the fabricated RF cavity by using a network analyzer, and the distribution of the electric field generated in the RF cavity was verified by a bead-pull measurement technique. RF conditioning and beam commissioning experiments were performed, following the fabrication and tuning of the RF cavity.