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arXiv · 2610.26616

Modeling and control of traveling wave structures with arbitrary beam loading

Zheqiao Geng·Riccardo Zennaro·Alessandro Citterio
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Abstract

Traveling wave (TW) structures are widely used in linear or circular accelerators for beam acceleration. Unlike the standing wave cavities, the overall accelerating voltage cannot be measured by the probes installed in the TW structures. This creates difficulties measuring and regulating the accelerating voltage and phase felt by the beam when it passes through the structure. In this paper, a model of TW structures is developed, allowing us to estimate the accelerating voltage and phase from the measurement of the RF drive power input to the TW structure. The beam loading effects, i.e., the beam-induced accelerating voltage and phase in the TW structure, are also included in the model. With the TW structure model, control methods are proposed to stabilize the accelerating voltage and phase felt by the beam based on feedback, feedforward, and optimization. The validity of the TW structure model is confirmed with the test results at the SwissFEL with improved beam stability under the same RF feedback controller. This work provides a firm basis for developing the multiple-bunch operation strategy for SwissFEL required by the future upgrade with more beamlines.

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Zheqiao Geng, Riccardo Zennaro, Alessandro Citterio. 2026-10-19. Modeling and control of traveling wave structures with arbitrary beam loading. https://arxiv.org/abs/2610.26616

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