Bremsstrahlung produced by electrons in the storage ring is a major concern in the radiation shielding design of synchrotron light sources, primarily arising from the Touschek effect and vacuum-related effect. Depending on the underlying mechanism, the resulting bremsstrahlung is classified as either solid or gas bremsstrahlung, both of which can propagate into beamline stations, especially from straight sections, thereby posing radiological risks to personnel and equipment.
With the advancement of fourth-generation synchrotron light sources based on diffraction-limited storage ring technology, the characteristics of bremsstrahlung radiation originating from straight sections have become increasingly complex, making earlier radiation source models no longer directly applicable. The objective of this study is to conduct an analysis of radiation sources in beamline stations of fourth-generation synchrotron facilities, clarify their respective contributions, and evaluate the implications of different modeling methodologies for shielding design. This study focuses on a representative beamline at the Hefei Advanced Light Facility. Three modeling approaches are developed and compared: (i) a simplified model, which assumes uniform electron losses throughout the storage ring with fixed-angle impacts on internal surfaces; (ii) a more refined model, which uses ELEGANT to accurately simulate electron loss positions and dynamics in straight sections, coupled with FLUKA to analyze the generation and transport of solid bremsstrahlung; and (iii) a gas bremsstrahlung model, which employs FLUKA to directly simulate electron–residual gas interactions.
The study compares the energy spectra, angular distributions, and spatial profiles of bremsstrahlung from the three models on the upstream wall of the first optical enclosure. Ambient dose equivalent distributions surrounding the enclosure are also evaluated. Results indicate that both solid and gas bremsstrahlung are major contributors to radiation levels in the beamline stations, each exhibiting distinct spatial and spectral characteristics. In addition, the study finds that the simplified model introduces significant deviations in the estimation of solid bremsstrahlung, highlighting the importance of accurately incorporating electron loss information in radiation simulations for beamline stations at fourth-generation synchrotron light sources to achieve reliable shielding assessments.
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