correctons

main/laserstab.tex

@@ -276,7 +276,7 @@ A picture of the experiment is in Fig. \ref{expsetup}.
 \begin{figure}[h!]
 \centering
 \includegraphics[scale=0.3]{images/result.png}
-\caption[Results of frequency stabilization tests]{Results of frequency stabilization with respect to th free running frequency noise: the in-loop red trace shows the frequency stabilized lasers as detected by the frequency counter, monitoring the beat-note between the two lasers in the lower frequency range. This trace is the best measurement we obtained below 1 Hz, where we reached 1.67 $\times$ 10$^4$ Hz/$\sqrt{Hz}$ at 0.05 Hz; The green trace is a test taken with the counter set to a higher frequency range: this test shows a result of 3.6 $\times$ 10$^4$ Hz/$\sqrt{Hz}$ at 1 Hz. This is also the test which showed the quietest results above 10 Hz, demonstrating that the HoQIs can reach a good level of stability in air. The black trace is the expected gain activated by the controllers, which is set to maximise the stabilization below 1 Hz.}
+\caption[Results of frequency stabilization tests]{Results of frequency stabilization with respect to th free running frequency noise: the in-loop red trace shows the frequency stabilized lasers as detected by the frequency counter, monitoring the beat-note between the two lasers in the lower frequency range. This trace is the best measurement we obtained below 1 Hz, where we reached 1.67 $\times$ 10$^4$ Hz/$\sqrt{Hz}$ at 0.05 Hz; The green trace is a test taken with the counter set to a higher frequency range: this test shows a result of 3.6 $\times$ 10$^3$ Hz/$\sqrt{Hz}$ at 1 Hz. This is also the test which showed the quietest results above 10 Hz, demonstrating that the HoQIs can reach a good level of stability in air. The black trace is the expected gain activated by the controllers, which is set to maximise the stabilization below 1 Hz.}
 \label{test}
 \end{figure}
 
@@ -305,7 +305,7 @@ This test confirmed also that HoQI2 is still noisier than HoQI1, especially in c
 The results of this experiment showed that it is possible to stabilize the frequency of the laser source of the 
 6D device using the technology presented: a compact, easy to handle setup which makes use of small
 interferometers of the same type that are used inside the 6D sensor. With this technology, we managed to reach a
-frequency stabilization of 8 $\times$ 10$^3$ Hz/$\sqrt{Hz}$ at 1 Hz, without the need of installing the
+frequency stabilization of 3.6 $\times$ 10$^3$ Hz/$\sqrt{Hz}$ at 1 Hz, without the need of installing the
 prototype in vacuum.\\
 This is already a promising result, but not yet sufficient for the requirements of 6D, especially below 1 Hz.
 The HoQIs are, at present times, too sensitive to external noise sources and hence it might

main/main.tex

@@ -49,7 +49,7 @@ Chiara Di Fronzo
 The discovery of gravitational waves opened a new way to look at the Universe and offered new opportunities to shed light on the still unknown aspects of physical sciences. The work presented in this thesis wants to give a contribution to the development of this new type of research: the author chose to focus on the improvement of the instruments able to detect the gravitational waves. This field is important to make the detectors more sensitive, in order to see more gravitational-wave sources and help to complete the mosaic of the astrophysical science. In particular, the detectors currently in use are interferometers, which are especially blind in a range of frequency below 30 Hz: this affects the chance to detect sources emitting in this frequency band.\\ 
 This lack of sensitivity is mainly due to seismic motion, and the work exposed in this thesis focussed on new techniques to lower this noise source and allow the instruments to be sensitive below 30 Hz.\\
 During the studies, the development and test of devices able to to potentially reduce the seismic motion have been performed, such as optical levers for tilt motion reduction and laser stabilization for low frequency readout; a new concept of the seismic system on one of the interferometers (LIGO) has also been proposed.\\
-The optical levers can in principle reduce tilt motion below 1 Hz; the use of capacitive position sensors in a new software configuration for LIGO can help to suppress ground motion by a factor of 3 in order of magnitude below 0.1 Hz. A competitive frequency stabilization to 8 $\times$ 10$^3$ Hz/$\sqrt{Hz}$ at 1 Hz for readout at low frequency is possible with a compact and easy to handle setup. These results are promising to provide suppression of the seismic motion in the bandwidth of interest and show that it is possible for a ground-based instrument to be seismically more stable and able to detect gravitational waves where it is now forbidden. 
+The optical levers can in principle reduce tilt motion below 1 Hz; the use of capacitive position sensors in a new software configuration for LIGO can help to suppress ground motion by a factor of 3 in order of magnitude below 0.1 Hz. A competitive frequency stabilization to 3.6 $\times$ 10$^3$ Hz/$\sqrt{Hz}$ at 1 Hz for readout at low frequency is possible with a compact and easy to handle setup. These results are promising to provide suppression of the seismic motion in the bandwidth of interest and show that it is possible for a ground-based instrument to be seismically more stable and able to detect gravitational waves where it is now forbidden. 
 
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