Thermal load assessment and design optimization of a double crystal monochromator under Korea-4GSR beamline conditions

초록

The Korea 4th generation storage ring (Korea-4GSR), featuring lower emittance and enhanced storage ring energy, is expected to provide photon beams of significantly higher brightness and coherence compared to the 3th-generation PLS-II (table 1). However, these high-flux and high-coherence photon beams impose considerable thermal loads on critical optical components such as the double crystal monochromator (DCM), potentially causing thermal deformation and increased slope errors on the crystal. And these effects degrade the beam quality and compromise the thermal stability of the DCM. This study aims to quantitatively evaluate the thermal response characteristics of the DCM under high heat-load conditions and to derive optimal cooling methods and structural design parameters. Using the PAL-DCM model from the PLS-II 9C beamline as a baseline, thermal loads were compared with those expected under the hard X-ray ID03 beamline at Korea-4GSR. We also analyzed the influence of various design parameters, including side and bottom cooling methods and crystal dimension variations, on the thermal and structural stability using a newly proposed DCM model. Simulations were conducted using OASYS (XOPPY) for incident power density calculations and ANSYS for thermo-mechanical coupling analysis. The results show that the newly proposed thermo-stable DCM (TS-DCM) design effectively mitigates thermal responses and reduces structural deformations under high heat-load conditions. This paper presents a quantitative analysis that clearly validates the performance enhancements of the proposed design.

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