Titolo della tesi: Automatic Alignment in Advanced Virgo+ Phase I and Effects of Radiation Pressure
The detection of Gravitational Waves through laser interferometers has proven itself to be an invaluable source of information about phenomena previously impossible to observe, like the coalescence of binary neutron stars and black holes. These machines are complex optomechanical systems of unusual scale, with cavities that span kilometers that need to be controlled with precision of the order of the picometer and the nanoradiant.
The main focus of this thesis is the Automatic Alignment of one such machines, Virgo, located near Pisa, Italy. Over the course of the thesis we explain the functioning principles of the interferometer and the difficult nature of the error signals used to control its degrees of freedom. We then focus on the Automatic Alignment, in particular on the simulation work carried out to establish a sensing strategy and how this prediction was then turned into the control of the angular degrees of freedom of the interferometer, with a final report of the performance of the alignment controls and the residual misalignment's rms of the interferometer's mirrors.
Over the course of this work we remark the importance of the effects of radiation pressure, that in machines like Virgo are visible on an unusual scale, with hundreds of kW of power impinging on suspended mirrors that weigh tens of kilograms. We explain briefly the linear approximation of radiation pressure historically used in Gravitational Wave detectors and then we propose the initial version of a non-linear model for this phenomenon, based on a variational approach.