Double-crystal monochromators (DCMs) are one of the most critical optical devices in beamlines at synchrotron sources, directly affecting the quality of the beam energy and position. As the performance of synchrotron light sources continues to improve, higher demands are placed on the stability of DCMs. This paper proposes a novel adaptive vibration control method combining variational modal decomposition (VMD) and filter-x normalized least mean squares (FxNLMS), ensuring DCM stability under random engineering disturbance. Firstly, the sample entropy of the vibration signal is selected as the fitness function, and the number of modal components k and the penalty factor α are optimized by a genetic algorithm. Subsequently, the vibration signal is decomposed into band frequencies that do not overlap with each other. Eventually, each band signal is individually governed by the FxNLMS controller. Numerical results have demonstrated that the proposed adaptive vibration control method has high convergence accuracy and excellent vibration suppression performance. Furthermore, the effectiveness of the vibration control method has been verified with actual measured vibration signals of the DCM.

In order to investigate the influence mechanism of various corrugated structures on the heat transfer of continuous annular concave-convex corrugated pipes, this paper examines the influence of corrugation height (Ch=1, 1.5 and 2 mm) and corrugation width (Cw=1, 1.5 and 2 mm) on the flow pattern, turbulent kinetic energy(TKE), Nusselt number (Nu), friction coefficient (f), and performance evaluation factor (PEF). Then, the correlation equations for Nu and f are established with different corrugated structural parameters. The results show that with the increase of Ch, the vortex number, TKE, and fin the pipe increase while Nude creases. The maximum PEF is 0.90 at Ch=1 mm. However, with the increase of Cw, the vortex number and Nuin the pipe increase, while TKE and fin the pipe do not change much. The maximum PEF is 0.87 at Cw=2 mm. Therefore, for this type of corrugated pipe, one should choose a small Chand a large Cw.

With the continuous development of synchrotron radiation light sources, higher requirements have been put forward for the stability of double-crystal monochromators in synchrotron radiation facilities. This paper designs an active adjustment mechanism for a double-crystal monochromator to improve its stability. Firstly, three spatial degrees of freedom are designed based on the active adjustment mechanism of flexible leaf spring parallel coupling, and the prototype of the mechanism is fabricated. Secondly, system identification experiments are carried out and the system transfer function curve is fitted by the nonlinear least squares method. Thirdly, the controller based on non-singular terminal sliding modes and a finite-time disturbance observer was designed for stability control and disturbance compensation. Finally, the effectiveness of the controller is verified by a model-in-the-loop approach based on the performance of the real-time target machine. The results show that the non-singular terminal sliding mode + finite-time disturbance observer control strategy can reduce the RMS value of the vibration displacement of Axis-1/Axis-2/Axis-3 by 81.25%, 78.53%, and 71.82%.

Tin contamination on extreme ultraviolet (EUV) collector mirrors significantly degrades mirror reflectivity. Hydrogen-based plasma cleaning is currently the standard method for removing the tin layer. However, to prevent substrate damage from over-cleaning, real-time monitoring of the tin layer thickness is critical. It has been established that the secondary electron yield (SEY) induced by high-energy primary electron bombardment correlates with the tin layer thickness. Thus, SEY can serve as a thickness indicator to determine the optimal cleaning endpoint. In this study, the evolution of secondary electrons during the cleaning process is simulated using a Particle-in-Cell (PIC) model combined with the Monte Carlo method, and the relationship between SEY and tin layer thickness is established. The simulation results indicate that under the specified conditions, H³⁺ is the dominant ionic species generated. Primary electrons account for nearly 24% of the incident particles, with an average energy of approximately 47 eV. Most secondary electrons possess energies below 30 eV, and their yield increases monotonically with the tin layer thickness, ranging from 0.60 to 1.05. These findings provide a novel approach for in situ detection of tin contamination layer evolution on EUV collector mirrors.

The double crystal monochromator (DCM) is a spectrometer in synchrotron radiation beamlines, and its stability directly impacts the quality of the emitted light. In order to meet the requirements of the fourth generation of synchrotron light sources, researchers have designed a DCM using an active control method to ensure stability by actively compensating for crystal displacement through voice coil motors. The active control method imposes high demands on the vibration isolation performance of the DCM frame. In response to external excitation characteristics, this paper proposes a quasi-zero stiffness (QZS) isolation system based on a compressed buckling beam structure. Random vibration simulations using finite element analysis revealed that, under different operating conditions, the 3σ displacement of the core part of the DCM is maintained at the nanometer level. Moreover, this paper presents a calculation method based on elastic potential energy to establish force equilibrium equations for negative stiffness and analyzes stress distribution in the beam during vibration using the derived deflection curve. Validation through finite element simulations confirms the method’s accuracy in calculating negative stiffness and stress distribution. Because of the structural similarities, some of the results of this paper can be applied to the study of negative stiffness honeycomb materials.