Design of Structural Stand for High-Precision Optics Microscopy

<p>Lawrence Livermore National Lab (LLNL) is home to the National Ignition Facility (NIF), the world’s largest and most energetic laser. Each of the 192 beamlines contains dozens of large optics, which require offline damage inspection using large, raster-scanning microscopes. The primary microscope used to measure and characterize the optical damage sites has a precision level of 1 µm. Mounted in a class 100 clean room with a raised tile floor, the microscope is supported by a steel stand that structurally connects the microscope to the concrete ground. Due to ambient vibrations experienced in the system, the microscope is only able to reliably reach a 10-µm level of precision.</p> <p>As NIF’s technology advances, there is a need to both increase optic measurement throughput and to measure damage sites at a higher level of precision. As a result, there is to be another microscope mounted into another clean room lab at LLNL. To assure the microscope can meet its specified level of precision, the stand on which it is mounted was designed to meet the rigorous <em>Environmental Vibrational Criteria</em> standards, or VC curves.</p> <p>Through the collection of random vibrational data using accelerometers and Power Spectral Density (PSD) analysis, the stand was designed to meet the VC-C curve requirement of velocities below 12.5 µm/sec. Furthermore, the stand design was optimized to avoid resonance at common vibrational signatures throughout the frequency spectrum, placing its first natural frequency at a sufficiently high level to minimize amplification.</p>

Name thesis:degree_name

MS in Mechanical Engineering

Discipline thesis:degree_discipline

Mechanical Engineering

Year dc:date.available

2020

Author dc:creator

• Novell, Sara T

Contributors dc:contributor

• Kim Shollenberger
• Mechanical Engineering
• College of Engineering

• Vibrations
• PSD
• Power Spectral Density
• FEA
• Transmissibility
• Accelerometer
• Acoustics, Dynamics, and Controls
• Applied Mechanics
• Computer-Aided Engineering and Design
• Energy Systems
• Structural Engineering

Identifier

10.15368/theses.2020.43

OAI identifier oai:identifier

oai:digitalcommons.calpoly.edu:theses-3629