# LIGO Document T1400668-v1

- Cryogenic silicon is being considered as an alternate material to the current material, silica, for the test masses in future iterations of LIGO due to its potential to reduce thermal noise. For example, the thermal expansion coefficient goes to zero at 120 K. This project maps the noise spectrum of low temperature silicon. The Fluctuation Dissipation Theorem relates the amount of noise produced by a system with the system's linear response to applied perturbations. We apply this theorem to cryogenic silicon by measuring the quality factor, Q, to observe the damping behavior. We can then calculate the noise spectrum of the system, and study the response of Q to frequency, drive amplitude, and temperature.

SURF2014_Marie_Lu

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