GMTNIRS, the first-generation instrument of the Giant Magellan Telescope, is a high-resolution (R = 65,000 – 80,000) near-infrared spectrograph. We introduce the preliminary design of optical mounts for slit, beam splitters, mirrors, and gratings installed in the cryogenic spectrograph. Optical components are mounted on aluminum structures and fixed by titanium springs and spring plungers. Static analysis of optical mounts with 1g-force at various directions has been performed to verify the stability of the optical system. In addition, stability in the seismic environment is evaluated with modal analysis and non-linear dynamic analysis. Design and simulation results are compared to the tolerance limits of the system.
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