- Open Access
Impedance characterization and optimization of the High Energy Photon Source in-vacuum undulator
Phys. Rev. Accel. Beams 28, 094401 – Published 11 September, 2025
DOI: https://doi.org/10.1103/ztx5-848v
Abstract
In storage ring-based synchrotron radiation light sources, in-vacuum undulators (IVUs) are widely used considering their advantages of short period length and high field quality. The impedance of the IVU and heat load deposition due to the beam passage are among the main concerns during the design and operation of the IVU. In this work, both transverse and longitudinal trapped modes are investigated, and novel mitigation strategies to reduce the impedance are proposed. Additionally, the longitudinal broadband impedance increase introduced by the bulge flexible taper transitions is presented. To obtain comprehensive and reliable information on the impedance, laboratory bench measurements are performed to identify the longitudinal and transverse impedance of the IVU experimentally. A reasonably good agreement was reached between the numerical predictions and the measurements.
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