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%\end{figure} %\end{figure}
\chapter{Reducing differential motion of aLIGO seismic platforms} \chapter{Reducing differential motion of aLIGO seismic platforms}
\noindent
During 2019, I spent some months working on LIGO Hanford site (Washington, USA). This experience allowed me to be critically involved in the complicated life of a gravitational-wave interferometer. In particular, I was given the opportunity to study how to improve LIGO performances at low-frequency, focussing on the reduction of seismic motion of the platforms where the optics live.\\ During 2019, I spent some months working on LIGO Hanford site (Washington, USA). This experience allowed me to be critically involved in the complicated life of a gravitational-wave interferometer. In particular, I was given the opportunity to study how to improve LIGO performances at low-frequency, focussing on the reduction of seismic motion of the platforms where the optics live.\\
In this chapter and in the following I am going to show you in detail how we can modify the software set up of LIGO in order to obtain a different and possibly better performance. This work has been developed in collaboration with LIGO Hanford and LIGO Livingston laboratories, Stanford University, MIT and UoB, and this chapter is partially including some technical notes I shared with LIGO collaboration. In this chapter and in the following I am going to show you in detail how we can modify the software set up of LIGO in order to obtain a different and possibly better performance. This work has been developed in collaboration with LIGO Hanford and LIGO Livingston laboratories, Stanford University, MIT and UoB, and this chapter is partially including some technical notes I shared with LIGO collaboration.
\section{Motivation: Duty cycle on LIGO} \section{Motivation: Duty cycle on LIGO}
Lock loss events are the main sources of preventing continuous observations for long periods of time: when light loses resonance in the cavities, a lock loss happens and the control system of the optical cavities are under effort to restore stabilization. This means that during lock loss the interferometer is no longer able to be stable and the observing time is interrupted.\\ Lock loss events are the main sources of preventing continuous observations for long periods of time: when light loses resonance in the cavities, a lock loss happens and the control system of the optical cavities are under effort to restore stabilization. This means that during lock loss the interferometer is no longer able to be stable and the observing time is interrupted.\\
Duty cycle is one of the main topic where commissioners focus on before starting an observing run. It is needed not only to observe more gravitational waves, but also to identify noise sources and improve sensitivity.\\ Duty cycle is one of the main topic where commissioners focus on before starting an observing run. It is needed not only to observe more gravitational waves, but also to identify noise sources and improve sensitivity.\\
Since the number of detected events over a time period N(t) is proportional to the volume of Universe under observation V, the observing time t and the rate R of astrophysical sources that can occur in a certain volume:\\ Since the number of detected events over a time period N(t) is proportional to the volume of Universe under observation V, the observing time t and the rate R of astrophysical sources that can occur in a certain volume:
\begin{equation} \begin{equation}
\centering \centering
...@@ -75,21 +73,20 @@ We started our design on chambers of x arm. Along this direction, the Input Mode ...@@ -75,21 +73,20 @@ We started our design on chambers of x arm. Along this direction, the Input Mode
\noindent \noindent
In the next section we will demonstrate that CPS are good witnesses to sense differential motion and they also can be used to lock the chambers with each other. In the next section we will demonstrate that CPS are good witnesses to sense differential motion and they also can be used to lock the chambers with each other.
\section{CPS Differential motion and locking} \section{Sensing differential motion via CPS}
Capacitive Position Sensors (CPS) measure the relative motion between two stages of the isolation system. On HAM chambers, they are are set between HEPI and ground, and between Stage 1 and HEPI. On BSC chambers, they also measure the relative motion between Stage 1 and Stage 2. Plots is Fig. \ref{diff} show the differential motion seen by the CPS between BSC and HAM chambers: the sensors are reliable for this measurement, and they put in evidence that the HAM chambers have a more synchronized motion with respect to the motion between HAM and BSC and BSCs only. This means that the block of HAM chambers on x arm is more relatively stable and can be used as driver for the other chambers, with the mode cleaner acting as witness.\\
\subsection{Sensing differential motion via CPS}
Capacitive Position Sensors (CPS) measure the relative motion between two stages of the isolation system. On HAM chambers, they are are set between HEPI and ground, and between Stage 1 and HEPI. On BSC chambers, they also measure the relative motion between Stage 1 and Stage 2. Plots is Fig. \ref{diff} show the differential motion seen by the CPS between BSC and HAM chambers: the sensors are reliable for this measurement, and they put in evidence that the HAM chambers have a more synchronized motion with respect to the motion between HAM and BSC and BSCs only. This means that the block of HAM chambers on x arm is more relatively stable and can be used as driver for the other chambers, with the mode cleaner acting as witness.
\begin{figure}[h!] \newpage
\begin{figure}[H]
\centering \centering
\includegraphics[scale=0.3]{images/ham2_ham3.PNG} \includegraphics[scale=0.3]{images/ham2_ham3.PNG}\\
\includegraphics[scale=0.3]{images/bs_itmx.PNG} \includegraphics[scale=0.3]{images/bs_itmx.PNG}\\
\includegraphics[scale=0.3]{images/bs_ham2.PNG} \includegraphics[scale=0.3]{images/bs_ham2.PNG}
\caption[CPS differential motion]{CPS differential motion between the HAM and BSC chambers along x axis. ISIs move in common, particularly in the same building. This can be confirmed by noting that the difference between two chambers is much lower than individual chambers.} \caption[CPS differential motion]{CPS differential motion between the HAM and BSC chambers along x axis. ISIs move in common, particularly in the same building. This can be confirmed by noting that the difference between two chambers is much lower than individual chambers.}
\label{diff} \label{diff}
\end{figure} \end{figure}
\newpage
\noindent \noindent
We projected the CPS of the x axis chambers to the suspension point in order to obtain PRCL and IMCL traces sensed by the CPS. For BSCs, we decided to sum the contributions of the CPSs on stage 1 and stage 2 and to project this sum.\\ We projected the CPS of the x axis chambers to the suspension point in order to obtain PRCL and IMCL traces sensed by the CPS. For BSCs, we decided to sum the contributions of the CPSs on stage 1 and stage 2 and to project this sum.\\
One of the main differences between the behaviour of CPS IMCL and CPS PRCL, is that the former is obviously involving only the HAM chambers. Since HAM2 and HAM3 have a very good common motion, IMCL can be considered more stable with respect to PRCL, which instead involves also BSCs. Indeed, CPS PRCL is following the only BSCs at frequencies below 0.02 Hz.\\ One of the main differences between the behaviour of CPS IMCL and CPS PRCL, is that the former is obviously involving only the HAM chambers. Since HAM2 and HAM3 have a very good common motion, IMCL can be considered more stable with respect to PRCL, which instead involves also BSCs. Indeed, CPS PRCL is following the only BSCs at frequencies below 0.02 Hz.\\
...@@ -97,13 +94,13 @@ Fig. \ref{sus} shows plots of PRCL and ICML by CPS projection to suspoint. These ...@@ -97,13 +94,13 @@ Fig. \ref{sus} shows plots of PRCL and ICML by CPS projection to suspoint. These
\begin{figure}[h!] \begin{figure}[h!]
\centering \centering
\includegraphics[scale=0.3]{images/CPS_SUSPOINT_IMCL.PNG} \includegraphics[scale=0.3]{images/CPS_SUSPOINT_IMCL.PNG}\\
\includegraphics[scale=0.3]{images/CPS_SUSPOINT_PRCL.PNG} \includegraphics[scale=0.3]{images/CPS_SUSPOINT_PRCL.PNG}
\caption[CPS suspoint projections]{CPS suspoint projections: IMCL and PRCL. The calibrated PRCL trace used as comparison has been de-whitened.} \caption[CPS suspoint projections]{CPS suspoint projections: IMCL and PRCL. The calibrated PRCL trace used as comparison has been de-whitened.}
\label{sus} \label{sus}
\end{figure} \end{figure}
\subsection{Locking chambers via CPS} \section{Locking chambers via CPS}
In the previous section we demonstrated that CPSs are good sensors for differential motion and can be used to monitor chamber motions at lower frequencies. Given that and remembering the aim of stabilize the motion of the chambers making them moving in sync, it is possible to use the CPSs to lock HAM2 and HAM3 together, HAM4 and HAM5 together, BSCs in the Corner Station together and BSCs hosting the ETMs together. This will stabilize the ISI differential motion with respect to a driving chamber.\\ In the previous section we demonstrated that CPSs are good sensors for differential motion and can be used to monitor chamber motions at lower frequencies. Given that and remembering the aim of stabilize the motion of the chambers making them moving in sync, it is possible to use the CPSs to lock HAM2 and HAM3 together, HAM4 and HAM5 together, BSCs in the Corner Station together and BSCs hosting the ETMs together. This will stabilize the ISI differential motion with respect to a driving chamber.\\
Since we saw that HAM2 and HAM3 show a very good common motion and that we can use the IMC as a witness of it, our first step has been to lock the HAM2 and HAM3 chambers together by feeding HAM3 a calculated differential CPS signal. This is done in practice with an additive offset to the setpoint of the HAM3 isolation control loop.\\ Since we saw that HAM2 and HAM3 show a very good common motion and that we can use the IMC as a witness of it, our first step has been to lock the HAM2 and HAM3 chambers together by feeding HAM3 a calculated differential CPS signal. This is done in practice with an additive offset to the setpoint of the HAM3 isolation control loop.\\
The block diagram in Fig. \ref{ham2b}, shows the structure of HAM2, where the signals from $d_{2}$ and $i_{2}$ represent the offsets given by CPS and inertial sensors.\\ The block diagram in Fig. \ref{ham2b}, shows the structure of HAM2, where the signals from $d_{2}$ and $i_{2}$ represent the offsets given by CPS and inertial sensors.\\
...@@ -490,3 +487,6 @@ We need to connect the ISI to the cavity and to do it we need to know how the PR ...@@ -490,3 +487,6 @@ We need to connect the ISI to the cavity and to do it we need to know how the PR
\caption{Block diagram of PRCL locked to ISI.} \caption{Block diagram of PRCL locked to ISI.}
\label{prcl} \label{prcl}
\end{figure} \end{figure}
\section*{Conclusions}
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main/laserstab.tex
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...@@ -248,8 +248,8 @@ Several tests have been taken in different conditions for noise hunting along th ...@@ -248,8 +248,8 @@ Several tests have been taken in different conditions for noise hunting along th
\begin{figure}[h!] \begin{figure}[h!]
\centering \centering
\includegraphics[scale=0.3]{images/test2807.png} \includegraphics[scale=0.3]{images/result.png}
\caption{Last laser stabilization test} \caption{Results of frequency stabilization: the in-loop red trace shows the frequency stabilization process as detected by the frequency counter monitoring the beat-note between the two lasers; the black trace is the expected gain activated by the controllers, which is set to maximise the stabilization below 1 Hz.}
\label{test} \label{test}
\end{figure} \end{figure}
...@@ -265,7 +265,8 @@ This test highlights also that HoQI2 is still noisier than HoQI1, despite the us ...@@ -265,7 +265,8 @@ This test highlights also that HoQI2 is still noisier than HoQI1, despite the us
\label{alt} \label{alt}
\end{figure} \end{figure}
\section{Beyond: installation onto the 6D device} \section*{Conclusions}
%installation into 6D
%\begin{thebibliography}{9} %\begin{thebibliography}{9}
% %
......
main/main.tex
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...@@ -7,6 +7,7 @@ ...@@ -7,6 +7,7 @@
\usepackage{graphicx} \usepackage{graphicx}
\usepackage[font=small,hang]{caption} \usepackage[font=small,hang]{caption}
\usepackage{subfigure} \usepackage{subfigure}
\usepackage{float}
\usepackage{array} \usepackage{array}
\usepackage{color} \usepackage{color}
\usepackage{colortbl} \usepackage{colortbl}
...@@ -24,7 +25,6 @@ ...@@ -24,7 +25,6 @@
\maketitle \maketitle
\frontmatter \frontmatter
\tableofcontents
\chapter{Statement of originality} \chapter{Statement of originality}
...@@ -32,25 +32,16 @@ ...@@ -32,25 +32,16 @@
A brief summary of the project goes here, with main results. A brief summary of the project goes here, with main results.
\chapter{Structure of this thesis} %dedica va qui
An introduction to frame the work and structure of the thesis go here.\\
STRUCTURE OF THESIS [DRAFT]\\ \chapter{Acknowledgements}
PART I: Gravitational astrophysics\\ Here I need to acknowledge for any funding (UoB, RAS, Caltech).
Chapter 1: Gravitational waves and sources\\
Chapter 2: low frequency window and multimessenger astronomy\\
PART II: Detectors and seismic isolation\\
Chapter 3: Interferometry and Advanced LIGO\\
Chapter 4: Inertial sensors and optical levers\\
PART III: Lowering seismic noise\\
Chapter 5: Seismic isolation at LHO\\
Chapter 6: Laser stabilization for 6D seismic isolation\\
Appendix A: first GW detection\\ \tableofcontents
Appendix B: control loops \listoffigures
\listoftables
\chapter{Notations} \chapter{Notations}
Useful notations, constants and formulas go here.\\ Useful notations, constants and formulas go here.\\
...@@ -70,6 +61,7 @@ AEI = Albert Einstein Institute\\ ...@@ -70,6 +61,7 @@ AEI = Albert Einstein Institute\\
aLIGO = Advanced Laser Interferometric Gravitational-wave Observatory\\ aLIGO = Advanced Laser Interferometric Gravitational-wave Observatory\\
AI = Anti-Imaging\\ AI = Anti-Imaging\\
ASD = Amplitude Spectral Density\\ ASD = Amplitude Spectral Density\\
BRS = Beam Rotation Sensors\\
BS = Beam Splitter\\ BS = Beam Splitter\\
BSC = Basic Symmetric Chamber\\ BSC = Basic Symmetric Chamber\\
BH = Black Hole\\ BH = Black Hole\\
...@@ -109,6 +101,7 @@ PBS = Polarizing Beam Splitter\\ ...@@ -109,6 +101,7 @@ PBS = Polarizing Beam Splitter\\
PD = PhotoDiode\\ PD = PhotoDiode\\
PR = Power Recycling\\ PR = Power Recycling\\
PRCL = Power Recycling Cavity Length\\ PRCL = Power Recycling Cavity Length\\
PSD = Power Spectral Density\\
QPD = Quadrant Position Device\\ QPD = Quadrant Position Device\\
RIN = Relative Intensity Noise\\ RIN = Relative Intensity Noise\\
SC = Sensor Correction\\ SC = Sensor Correction\\
...@@ -117,6 +110,26 @@ SRCL = Signal Recycling Cavity Length\\ ...@@ -117,6 +110,26 @@ SRCL = Signal Recycling Cavity Length\\
TEC = Thermo-Electric Controller\\ TEC = Thermo-Electric Controller\\
UoB = University of Birmingham\\ UoB = University of Birmingham\\
\chapter{Structure of this thesis}
An introduction to frame the work and structure of the thesis go here.\\
STRUCTURE OF THESIS [DRAFT]\\
PART I: Gravitational astrophysics\\
Chapter 1: Gravitational waves and sources\\
Chapter 2: low frequency window and multimessenger astronomy\\
PART II: Detectors and seismic isolation\\
Chapter 3: Interferometry and Advanced LIGO\\
Chapter 4: Inertial sensors and optical levers\\
PART III: Lowering seismic noise\\
Chapter 5: Seismic isolation at LHO\\
Chapter 6: Laser stabilization for 6D seismic isolation\\
Appendix A: first GW detection\\
Appendix B: control loops
\mainmatter \mainmatter
\part{Gravitational-wave frontiers} \part{Gravitational-wave frontiers}
...@@ -127,20 +140,19 @@ UoB = University of Birmingham\\ ...@@ -127,20 +140,19 @@ UoB = University of Birmingham\\
\part{Lowering seismic motion} \part{Lowering seismic motion}
\include{oplevs} \include{oplevs}
\include{CPSdiff} \include{CPSdiff}
%\include{LSCdiff}
\include{laserstab} \include{laserstab}
\appendix \appendix
\include{A} \include{A}
\include{B} \include{B}
%\appendix C on my work in LIGO labs
\backmatter \backmatter
\listoffigures
\listoftables
\begin{thebibliography}{} \begin{thebibliography}{}
%chapt 1
\bibitem{wei} S. Weinberg \textit{Gravitation and Cosmology: principles and applications of the General Theory of Relativity}, John Wiley \& Sons, Inc., 1972 \bibitem{wei} S. Weinberg \textit{Gravitation and Cosmology: principles and applications of the General Theory of Relativity}, John Wiley \& Sons, Inc., 1972
\bibitem{nar} J. V. Narlikar \textit{An introduction to Relativity}, Cambridge University Press, 2011 \bibitem{nar} J. V. Narlikar \textit{An introduction to Relativity}, Cambridge University Press, 2011
...@@ -149,6 +161,8 @@ UoB = University of Birmingham\\ ...@@ -149,6 +161,8 @@ UoB = University of Birmingham\\
\bibitem{first} B. P. Abbott, \textit{Observation of Gravitational Waves from a Binary Black Hole Merger}, Phys. Rev. Lett. 116, 061102, 2016 \bibitem{first} B. P. Abbott, \textit{Observation of Gravitational Waves from a Binary Black Hole Merger}, Phys. Rev. Lett. 116, 061102, 2016
%chapt3
\bibitem{ligo} Advanced LIGO Systems Group, \textit{Advanced LIGO Systems Design}, DCC document T010075-v3, 2017 \bibitem{ligo} Advanced LIGO Systems Group, \textit{Advanced LIGO Systems Design}, DCC document T010075-v3, 2017
\bibitem{abb} B. P. Abbott et al, \textit{GW150914: The Advanced LIGO Detectors in the Era of First Discoveries}, Phys. Rev. Lett. 116, 131102, 2016 \bibitem{abb} B. P. Abbott et al, \textit{GW150914: The Advanced LIGO Detectors in the Era of First Discoveries}, Phys. Rev. Lett. 116, 131102, 2016
...@@ -160,7 +174,41 @@ Beginning of Gravitational Wave Astronomy} ...@@ -160,7 +174,41 @@ Beginning of Gravitational Wave Astronomy}
\bibitem{lsc} K. Izumi, D. Sigg, \textit{Advanced LIGO: length sensing and control in a dual recycled interferometric gravitational wave antenna}, 2017 Class. Quantum Grav. 34 015001 \bibitem{lsc} K. Izumi, D. Sigg, \textit{Advanced LIGO: length sensing and control in a dual recycled interferometric gravitational wave antenna}, 2017 Class. Quantum Grav. 34 015001
\bibitem{poster} \textit{https://dcc.ligo.org/LIGO-G1900741} %oplev
\bibitem{phd} D. Tuyenbayev, \textit{Extending the scientific reach of Advanced LIGO by compensating for temporal variations in the calibration of the detector.}, PhD thesis, University of Texas, 2017
\bibitem{intro} B. Lantz et al., \textit{Estimates of HAM-ISI motion for A+}, T1800066-v2, March 2018, https://dcc.ligo.org/LIGO-T1800066
\bibitem{intro2} S. Cooper et al., \textit{Ham ISI model}, Technical note, University of Birmingham, March 2018, https://dcc.ligo.org/LIGO-T1800092
\bibitem{ven} Venkateswara et al., \textit{Subtracting tilt from a horizontal-seismometer using a ground-rotation-sensor}, Bulletin of the Seismological Society of America (2017) 107 (2): 709-717
\bibitem{mca} C. Di Fronzo \textit{Optical sensors for improving low-frequency performance in GW detectors}, Mid-Course Assessment, University of Birmingham, 2018
\bibitem{poster2} C. Di Fronzo et al., \textit{Optical Lever for interferometric inertial isolation}, poster, LVC meeting, Maastricht 2018, https://dcc.ligo.org/LIGO-G1801693
\bibitem{sina} S. M. Köhlenbeck, \textit{Towards the SQL Interferometer Length Stabilization at the AEI 10 m-Prototype}, PhD thesis, Gottfried Wilhelm Leibniz Universität Hannover, 2018
\bibitem{J} R.V. Jones et al., \textit{Some developments and applications of optical levers}, 1961 J. Sci. Instrum. 38 37
\bibitem{kaz} K. Agatsuma, \textit{Optical lever for KAGRA}, GW monthly seminar at Tokyo, 2014
\bibitem{lan} B. Lantz et al. \textit{Review: Requirements for a Ground Rotation Sensor to Improve Advanced LIGO}, Bulletin of the Seismological Society of America, Vol. 99, No. 2B, 2009
\bibitem{coll} C. Collette et al. \textit{Review: Inertial Sensors for Low-Frequency Seismic Vibration Measurement}, Bulletin of the Seismological Society of America, Vol. 102, No. 4, 2012
\bibitem{dan} D. E. Clark, \textit{Control of Differential Motion Between Adjacent Avanced LIGO Seismic Isolation Platforms}, PhD thesis, Stanford University, 2013
\bibitem{ast} S. M. Aston at al., \textit{Update on quadruple suspension design for Advanced LIGO}, Class. Quantum Grav., 29 (2012) 235004 (25pp)
\bibitem{image} B. Shapiro, \textit{Brief Introduction to Advanced LIGO Suspensions}, LAAC Talk, August 2014, https://dcc.ligo.org/LIGO-G1400964
%cpsdiff
%6D
\bibitem{poster} C. Di Fronzo et al, \textit{A 6D inertial isolation system}, ET Symposium, 2019, poster, https://dcc.ligo.org/LIGO-G1900741
\bibitem{6d} C.M. Mow-Lowry, D. Martinov, \textit{A 6D interferometric inertial isolation system}, 2019 Class. Quantum Grav. 36, 24 \bibitem{6d} C.M. Mow-Lowry, D. Martinov, \textit{A 6D interferometric inertial isolation system}, 2019 Class. Quantum Grav. 36, 24
...@@ -174,22 +222,12 @@ Beginning of Gravitational Wave Astronomy} ...@@ -174,22 +222,12 @@ Beginning of Gravitational Wave Astronomy}
\bibitem{adj} $https://www.photonicsolutions.co.uk/upfiles/ADJUSTIKFiberLaserLG13Dec17.pdf$ \bibitem{adj} $https://www.photonicsolutions.co.uk/upfiles/ADJUSTIKFiberLaserLG13Dec17.pdf$
\bibitem{mephi} $https://edge.coherent.com/assets/pdf/COHR\_ MephistoNPRO\_ WP\_ 9\_ 24\_ 19.pdf$ \bibitem{mephi} $https://edge.coherent.com/assets/pdf/COHR\_ MephistoNPRO$
\bibitem{phd} D. Tuyenbayev, \textit{Extending the scientfic reach of Advanced LIGO by compansating for temporal variations in the calibration of the detector.}, PhD thesis, University of Texas, 2017
\bibitem{intro} B. Lantz et al., \textit{Estimates of HAM-ISI motion for A+}, T1800066-v2, March 2018, https://dcc.ligo.org/LIGO-T1800066
\bibitem{intro2} S. Cooper et al., \textit{Ham ISI model}, Technical note, University of Birmingham, March 2018, https://dcc.ligo.org/LIGO-T1800092
\bibitem{ven} Venkateswara et al., \textit{Subtracting tilt from a horizontal-seismometer using a ground-rotation-sensor}, Bulletin of the Seismological Society of America (2017) 107 (2): 709-717
\bibitem{mca} C. Di Fronzo \textit{Optical sensors for improving low-frequency performance in GW detectors}, Mid-Course Assessment, University of Birmingham, 2018
\bibitem{poster} C. Di Fronzo et al., \textit{Optical Lever for interferometric inertial isolation}, poster, LVC meeting, Maastricht 2018, https://dcc.ligo.org/LIGO-G1801693
\end{thebibliography} \end{thebibliography}
\chapter{Acknowledgements}
\end{document} \end{document}
\ No newline at end of file
main/oplevs.tex
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