Measurement of Thermal Noise Thermal noise is the displacement noise of a suspended mass due to its temperature and the temperature of the suspension. In the past the thermal noise of a suspended mass has only been measured near its resonance frequency. The fluctuation-dissipation theorem has then been used to predict the noise at frequencies outside its resonance. Though this theorem has been proven, the frequency dependence it predicts depends on the damping mechanism. This may not be well known or understood.
Thermal noise is particularly important in interferometric gravitational wave detection systems.
It is the noise source which limits the sensitivity of a detector at low frequencies. Such systems are assumed to have low dissipation. We intend to set up a displacement noise frequency distribution measuring apparatus. It will measure the total displacement noise performance of existing suspension systems and enable the design of future systems to be improved. What is important is determine the achievable noise floors and characterise the noise.