Longitudinal bunch size measurement using an RF deflector

It is extremely important to diagnose beams in accelerators to improve accelerator operation. In the low velocity section of a proton or heavy ion linac, the diagnostic method for longitudinal beam properties is less established compared to that for transverse properties. We have developed a new diagnostic method for the longitudinal bunch size by utilizing an RF deflector. We evaluated the uncertainty in bunch size measurement through simulation, and it was obtained as 0.5°. In addition, we measured longitudinal beam emittance through bunch size measurements at several RF amplitudes of an upstream buncher. The measured emittance was 0.13±0.01π deg.MeV, which was consistent with the simulation result.