Design studies of a continuous-wave normal conducting buncher for European X-FEL

TL;DR

This paper presents the design and optimization of a continuous-wave normal conducting buncher for the European XFEL upgrade, focusing on RF geometry, power coupling, thermal management, and multipacting prevention.

Contribution

It introduces a novel RF design with optimized geometry, power coupler, and cooling scheme for a CW normal conducting buncher in XFEL applications.

Findings

Achieved high shunt impedance and large mode separation.

Designed a tapered waveguide RF power coupler with field asymmetry compensation.

Developed a simplified cooling scheme based on multiphysics simulations.

Abstract

A three-cell 1.3 GHz, Normal Conducting (NC) buncher is designed for a possible future upgrade of the European XFEL to operate in a continuous-wave (CW) / long pulse (LP) mode. The RF geometry of the buncher is optimized for high shunt impedance, large mode separation as well as multipacting free in the operation range. The bunchersupport cavity voltage of 400 kV with an RF power dissipation of 14 kW. A tapered waveguide-based RF power coupler is designed to feed the RF power to the buncher. The RF power coupler port is optimized for field asymmetry compensation. The thermal load due to RF power dissipation is analyzed using Multiphysics simulations in CST and a simplified cooling scheme is designed.