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This study investigates three mounting methods—clamping, soldering, and a hybrid clamping–soldering approach—for cryogenically cooled thin diamond crystals crucial to stable operation of X-ray Free Electron Laser (XFEL) systems. While clamping methods exhibit temperature resilience and flexibility, meticulous design is required to prevent stress-induced warping and reduce thermal contact area. Soldering methods offer reliable mechanical and thermal bonding but encounter challenges due to the coefficient of thermal expansion mismatch at cryogenic temperatures. The hybrid method, integrating clamping and soldering with strain relief cuts, effectively mitigates overall distortion caused by mounting and XFEL thermal loads. These findings offer a novel mounting solution for high-performance x-ray optics in XFEL research and applications, ensuring stability and optimal functionality in cryogenic conditions. [ABSTRACT FROM AUTHOR]

With dramatically improved brightness and repetition rate, the thermal load for crystal optics in x-ray free-electron laser applications has also significantly increased. To mitigate the thermal load, one effective method is cryogenic cooling. However, the emerging nondiffusive heat transfer phenomenon at cryogenic temperature may cause design failure if overlooked. To evaluate the optical performance of thin crystal optics under thermal load at cryogenic temperature, an integrated numerical tool is presented and applied to characterize the thermal load on thin crystals with nondiffusive phenomena accounted. Significant thermally induced distortion of the rocking curve is observed from numerical simulation, leading to potential seed power reduction in hard x-ray self-seeding application. Cryogenic cooling is confirmed necessary by simulation to handle the thermal load at high repetition rate operation. [ABSTRACT FROM AUTHOR]

Stanford Synchrotron Radiation Lightsource serves a wide scientific community with its variety of X‐ray capabilities. Recently, a wiggler X‐ray source located at beamline 10‐2 has been employed to perform high‐resolution rocking curve imaging (RCI) of diamond and silicon crystals. X‐ray RCI is invaluable for the development of upcoming cavity‐based X‐ray sources at SLAC, including the cavity‐based X‐ray free‐electron laser and X‐ray laser oscillator. In this paper, the RCI apparatus is described and experimental results are provided to validate its design. Future improvements of the setup are also discussed. [ABSTRACT FROM AUTHOR]

We present a new mounting design for thin crystal optics with cryogenic cooling compatibility. We design a crystal geometry with two symmetric strain-relief cuts to mitigate the distortion from mounting. We propose to sputter gold onto the crystal and the holder to ensure excellent thermal contact and sufficient mechanical bonding. The system is analyzed and verified by finite element analysis to have an acceptable level of strain due to mounting. The thermal performance of this mounting scheme is validated in an example cryogenic cooling system and the results indicate a tolerance of power density up to ∼1 kW/mm2. [ABSTRACT FROM AUTHOR]

X‐ray free‐electron lasers (XFELs) open a new era of X‐ray based research by generating extremely intense X‐ray flashes. To further improve the spectrum brightness, a self‐seeding FEL scheme has been developed and demonstrated experimentally. As the next step, new‐generation FELs with high repetition rates are being designed, built and commissioned around the world. A high repetition rate would significantly speed up the scientific research; however, alongside this improvement comes new challenges surrounding thermal management of the self‐seeding monochromator. In this paper, a new configuration for self‐seeding FELs is proposed, operated under a high repetition rate which can strongly suppress the thermal effects on the monochromator and provides a narrow‐bandwidth FEL pulse. Three‐dimension time‐dependent simulations have been performed to demonstrate this idea. With this proposed configuration, high‐repetition‐rate XFEL facilities are able to generate narrow‐bandwidth X‐ray pulses without obvious thermal concern on the monochromators. [ABSTRACT FROM AUTHOR]

Thermal load has been a haunting factor that undermines the brightness and coherence of the self‐seeded X‐ray free‐electron laser. Different from uniformly pulsed mode, in pulse train mode a thermal quasi‐steady state of the crystal monochromator may not be reached. This leads to a dynamic thermal distortion of the spectral transmission curves and seed quality degradation. In this paper, the pulse‐to‐pulse thermal load effects on the spectral transmission curves and seed quality are shown, and some instructive information for the tuning process is provided. [ABSTRACT FROM AUTHOR]

Non-uniform thermal load causes performance degradation of crystal X-ray optics. With the development of high-brightness X-ray free-electron lasers, the thermal load on X-ray optics becomes even more severe. To mitigate the thermal load, a quantitative understanding of thermal effects on the optical performance is necessary. We derived an analytical model for monochromator performance under a non-uniform thermal load. This analytical model quantitatively describes the distortion of the rocking curve and attributes different contributions to different factors of thermal load. It provides not only monochromator design insights and considerations, but also a quick estimation of the rocking curve distortion due to thermal load for practical situations such as pump-probe experiments.