Speaker
Description
Gravitational wave detectors are complex instruments requiring precise adjustments of their parameters, particularly optical ones, to achieve the highest possible sensitivity. During commissioning, difficulties and problems limiting the sensitivity are identified. Simulations of these detectors play a key role in understanding these phenomena, resolving them, and preparing for future improvements.
On the Virgo ground-based detector, tuning of the optical cavities is a challenging task that requires adjusting numerous parameters within a very short time. In order to perform this task, a thorough understanding of the detector parameters and the phenomena that affect them is necessary. Therefore, precise and robust characterization of the parameters and the effects that affect them is necessary. The method of characterization can be completed with simulation in order to better interpret the results obtained.
In this work, we performed many characterizations of the 3 km long Fabry-Perot cavities of the Virgo ground-based detector. Measurements of the radius of curvature of the test masses have been performed in several thermal states in order to evaluate the effects involved in the shift from the ex-situ measurement. For the first time, we have experimentally measured the impact of the cryotrap facing the test masses which can offset the RoC by several meters, and create a negative lens in the subsrates with a focal length of the order of 100km. The characterization in different thermal states has been completed with measurements of astigmatism.