Thermal optimization of a high-heat-load double-multilayer monochromator

Area of Science:

• Materials Science
• Optics
• Synchrotron Radiation Technology

Background:

• High heat loads from synchrotron undulator beams cause thermal deformation in multilayer optics.
• Accurate thermal management is crucial for maintaining beam quality in advanced X-ray beamlines.

Purpose of the Study:

• To investigate thermal deformation in multilayer mirrors subjected to undulator beam heat loads.
• To optimize multilayer substrate geometry for minimizing thermally induced slope errors.
• To analyze the impact of geometry on focusing properties and residual slope errors.

Main Methods:

• Finite-element analysis (FEA) was employed to model thermal deformation.
• The study focused on the ESRF-EBS upgrade beamline EBSL-2.
• Optimization of multilayer substrate geometry was performed to minimize slope errors.

Main Results:

• Non-uniform heat load distribution was observed due to reflected heat.
• Optimized geometry minimized thermal bending, resulting in focal lengths down to 100 m (meridional) and 2000 m (sagittal).
• Residual slope errors were found to be 0.1-0.25 µrad, largely unaffected by geometry, but mitigated in the sagittal direction by the sin(θ) factor.

Conclusions:

• Multilayer mirror geometry optimization is essential for mitigating thermal deformation and slope errors.
• The 'smart cut' depth requires careful consideration of reflected heat load for accurate thermal bending control.
• Effective management of thermal effects is critical for high-precision focusing in synchrotron radiation applications.