Design and Analysis of a Crystalline Silicon Triangular Vertical Spring Blades-cryogenics Suspension System for the Einstein Telescope Observatory

This thesis explores the design and optimization of crystalline silicon triangular blade springs, the main component of the vertical suspension system for test masses in the Einstein Telescope (ET), a third-generation gravitational wave observatory. The primary objective is to enhance the cryogenic suspension system's performance by focusing on several key areas. Firstly, the design aims to reduce thermal noise by leveraging the high quality factor (Q-factor) of crystalline silicon, which is associated with low mechanical losses, the blades minimize internal friction and energy dissipation, contributing to the performance of the cryogenic suspension system Secondly, the design focuses on increasing thermal conductivity. Crystalline silicon's high thermal conductivity at low temperatures, along with the design of the blades, ensures efficient heat dissipation and uniform temperature distribution. These properties help maintain the low temperatures required for cryogenic operation, stabilizing the system and reducing noise. Additionally, the design addresses compensation for mechanical mismatches by selecting cryogenic materials with compatible thermal expansion coefficients for the suspension components and incorporating flexible joints. This approach reduces the thermal stress and enhances structural integrity at low temperatures. By operating at cryogenic temperatures, the properties of the materials and the design of the blades ensure the mechanical integrity and longevity of the suspension system, effectively reducing mechanical stress and deformation caused by thermal variations. Furthermore, providing effective vibration isolation is another primary goal. The vertical spring blades are optimized to attenuate seismic and other mechanical vibrations, preventing them from affecting the sensitive components of the interferometer. This isolation for maintaining the precision and accuracy of gravitational wave measurements. Lastly, ensuring mechanical stability is paramount. The design maintains the dimensional stability and rigidity of the blades under cryogenic conditions, ensuring consistent performance and precise alignment of the suspended components. By addressing these objectives, the thesis aims to enhance the cryogenics suspension system sensitivity by minimizing surface stress and optimizing the natural frequency of the blades. Utilizing ANSYS simulations, parameters such as length, width, and thickness of the crystalline silicon blades are precisely adjusted. A dual-load approach, applying 100-kg for two-blade and 50-kg for four-blade designs, determines the impact of various crystalline orientations on mechanical stress and natural frequencies, introducing design flexibility to improve performance and reduce noise. The study integrates theoretical models with Finite Element Analysis (FEA) to refine blade geometry, aiming to optimize the design. Crystalline silicon blades are designed to function as thermal channels in cryogenic environments while compensating for suspension beam tolerances. Experimental validation through wire electrical discharge machining (WEDM) of smaller, thinner silicon samples corroborates simulation predictions and enhances the reliability of the design. Validation through WEDM demonstrates that the surface stress on the blades remains below the experimentally determined maximum breaking strength. The findings suggest potential improvements, including local feedback mechanisms to further attenuate natural frequencies, particularly in cryocooler noise filtration. This research advances the understanding of vertical spring crystalline silicon blades, offering insights for future applications in precision instrumentation and gravitational wave detection. The integration of modeling, simulations, and experimental results marks a contribution to the field, paving the way for future research.