\chapter{Assembling suspension chains for A+ at LHO}
\label{A}
In 2019 I spent some months working on LIGO Hanford site. Along with the study exposed in Chapter 5, I offered my lab experience in building the HSTS suspensions to be installed for the A+ upgrade. The assembly team was composed by me, Dr. Rahul Kumar and Dr. Jeff Bartlett. The suspensions have been installed in 2021 under the supervision of Rahul. Here there is a gallery of original photos of the lab work done together. It was an intense and very interesting team work, which enhanced my skills in working into a clean room, with delicate structures that needed to be assembled very precisely.
In 2019 I spent some months working on LIGO Hanford site. Along with the study exposed in Chapter 5, I offered my lab experience in building the HSTS (HAM Small Triple Suspension) to be installed for the LIGO A+ upgrade. The assembly team was composed by me, Dr. Rahul Kumar and Dr. Jeff Bartlett. The suspensions have been installed in 2021 under the supervision of Rahul in HAM7 and HAM8, and will be known as Filter Cavities (FC). The FC will enhance squeezing capabilities and help improve the quantum noise. Here there is a gallery of original photos of the lab-work done together. It was an intense and very interesting team work, which enhanced my skills in working into a clean room, with delicate structures that needed to be assembled very precisely.
\begin{figure}
\centering
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@@ -11,13 +11,13 @@ In 2019 I spent some months working on LIGO Hanford site. Along with the study e
\caption[Preparing the suspending wires]{Left: one of the wire used to suspend the test mass. Right: Technique to prepare the wire with the right tension: a given weight is applied and left for 5 minutes.}
\caption[Preparing the suspending wires]{Left: one of the wire used to suspend the test mass. The wires suspending the bottom mass are stainless steel wires, 0.0047 inches-thick. The upper stages are suspended by 0.008 inches-thick wires. Right: Technique to prepare the wire with the right tension: a given weight is applied and left for 5 minutes.}
\caption[Mounting the wires and their support]{Mounting the wires for the test mass suspension on their support. Right: Jeff and I while installing the wire support into the suspension cage.}
\caption[Mounting the wires and their support]{Mounting the wires for the test mass suspension on their support. Right: Jeff and I while installing the wire support into the suspension cage.}
\end{figure}
\begin{figure}
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@@ -25,7 +25,7 @@ In 2019 I spent some months working on LIGO Hanford site. Along with the study e
\caption[Installing the test masses]{Top: Rahul and I installing the bottom test mass and suspending it with the wires. Bottom: Rahul while measuring the alignment of the test mass into the suspension cage.}
\caption[Installing the test masses]{Top: Rahul and I installing the bottom test mass and suspending it with the wires. The bottom mass is a mirror of 2.8 Kg. Bottom: Rahul while measuring the alignment of the test mass into the suspension cage.}
@@ -116,7 +116,6 @@ Noise sources make LIGO blind in some frequency windows: current technological l
Noises can be of fundamental, technical and environmental origin. Fundamental noises come from first principles, and they determine the ultimate design sensitivity of the instrument. They include thermal and quantum noises, and they cannot be reduced without a major instrument upgrade which involves structural changes. Quantum noise includes shot noise of the sensors, causing power fluctuations, and radiation pressure, resulting in a physical displacement of the test masses. Thermal noise arises from the suspensions and the optical coatings and dominates in the 5-100 Hz frequency range.\\
Technical noises arise from electronics, control loops, charging noise and other effects; environmental noises include seismic motion, acoustic and magnetic noises: these noises can be reduced once identified and carefully studied.\\
\noindent
This thesis focuses on the improvement of the seismic isolation system. Seismic motion is measured using inertial sensors which are placed on the suspension benches. The residual motion effects the stability of the resonant cavities and limits the sensitivity of the detector in the low frequency band. The goal is to provide solutions to reduce seismic motion and improve the detector sensitivity.
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@@ -124,9 +123,9 @@ This thesis focuses on the improvement of the seismic isolation system. Seismic
\label{ligosei}
Every optic needs to be stable with respect to seismic motion, because movements in the mirrors will cause unwanted displacement of the laser beam on the optical surface, resulting in noise during the laser travel into the cavities and then at the output. The main mirrors (test masses and beam splitter) are suspended from a stabilized bench and every suspension chain is placed in vacuum chambers called \textit{Basic Symmetric Chambers} (BSC). The auxiliary optics are placed on optical benches enclosed in the \textit{Horizontal Access Module} (HAM) chambers.
\begin{figure}[H]
\begin{figure}[h!]
\centering
\includegraphics[scale=0.75]{images/chambers.png}
\includegraphics[scale=0.7]{images/chambers.png}
\caption[Advanced LIGO vacuum system]{Schematic view of the vacuum chambers enclosing the optics \cite{mat}. There are 5 BSCs and 6 HAMs, for a total of 11 vacuum chambers for each LIGO. Each chamber provides a mixture of passive-active isolation from seismic motion, using pendulums, inertial sensors and hydraulic systems.}
@@ -37,7 +37,8 @@ The major advantages is that this system can improve sensitivity, thermal noise,
\noindent
What we expect from 6D is isolation at low frequencies and reduction of fundamental noises: the thermal noise of the suspension is suppressed by the quasi-monolithic, fused-silica fibre; temperature gradients are kept under control thanks to the vacuum enclosure.\\
The expected performance is shown in Fig. \ref{6dsens}: the 6D isolator provides an improvement of the performance of more than two orders of magnitude with respect to what is possible with state of the art seismometers \cite{6d}.\\
The control noise will become negligible above 5Hz because the bandwidth for the control loops will be reduced to 0.5 Hz.
%The control noise will become negligible above 5Hz because the bandwidth for the control loops will be reduced to 0.5 Hz.
@@ -340,22 +340,12 @@ Beginning of Gravitational Wave Astronomy}
%\chapter*{Grazie!}
%\addcontentsline{toc}{chapter}{Grazie!}
%On a personal note, \textit{grazie} Conor for always being supportive, it was important in the hardest times! Grazie, with great respect.\\
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%To my best friend here in the UK: \textit{grazie} Sam for your presence, your help, your effort to endure the enormous emotional baggage of this stubborn Italian one, who wanted to be your friend at all costs. I know it was not easy, I will not forget it.\\
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%\textit{Grazie} to all my PhD colleagues who shared the stress and the fun of this experience with me. Riccardo, thanks for pushing me to go further, do better, stay stronger. George, thank you for the chess \& Czech classes, you opened my mind. Amit, your positivity is always contagious, thank you for sharing it!\\
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%I really need to thank all the people on LIGO Hanford, who made me feel included and part of a great family. \textit{Grazie} Jenny, Jim, Rahul and Jeff B. for your infinite patience and for teaching me so much of LIGO; and I was very lucky to meet Dripta, an amazing housemate and friend, thank you for all the time you chose to share with me.\\
%\textit{Grazie} to my family in Seattle, zia Claudia, zio Carlo, Rossana \& Jim, Carla \& Wayne, who helped me to feel at home during my stay in the USA.\\
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%\noindent
%To my friends in Italy: Vero \& Ludo, Alice \& Anna Paola, Martina, Francesca, Edo \& Nani, \textit{grazie} for your incredible will to stay close to me despite the 2000 km-distance.\\
%Angela and Anna, \textit{grazie} for your presence and friendship in Birmingham.\\
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%\noindent
%A mio nonno, zio Marco e zia Laura, zia Flora e zio Vincenzo, grazie per avermi riempito di affetto e di cibo, sono stati indispensabili.\\
%Ai miei genitori e a mia sorella, grazie per avermi sempre incoraggiato, ascoltato le mie lamentele e sopportato la distanza durante questi 4 anni cosi' importanti per me.
