LINAC2026 - 33rd Linear Accelerator Conference

Electromagnetic design study of a 500 MHz sub-harmonic buncher cavity for the PLS-II linac

Not scheduled

2h

Daejeon Convention Center

Poster Presentation MC4.A07: Room temperature RF Poster Session

Speaker

Mr Geunwoo Kim (Pohang University of Science and Technology)

Description

The PLS-II is considering nonlinear-kicker (NLK) injection to reduce stored-beam perturbations. This scheme requires the linac to deliver a dominant bunch with a reduced energy spread. However, the present S-band pre-buncher and buncher generate multiple bunches, leading to RF-phase-dependent capture conditions and possible injection instability. A previous study using a 500 MHz sub-harmonic buncher (SHB) model based on 2D SUPERFISH calculations showed that replacing the pre-buncher reduced the rms energy spread from 10 MeV to 1.1 MeV and produced a dominant bunch at the end of the simulated injector section. To support further evaluation, this work develops a simulation-based electromagnetic model of a 500 MHz SHB cavity. The cavity is designed using CST eigenmode simulations and is evaluated in terms of the resonant frequency, effective gap voltage, shunt impedance, intrinsic quality factor, transit-time factor, and peak surface field. The cavity-derived longitudinal field is used in particle tracking to assess its effect on bunching and energy spread. This study provides the electromagnetic design basis for evaluating a 500 MHz SHB option for the PLS-II linac.