Ground-based gravitational wave detectors are evolving at a rapid pace. In the five minutes that followed the first direct detection of gravitational waves, the Advanced LIGO and Advanced Virgo experiments have been subject to substantial upgrades, increasing their sensitivities by many times and allowing them to detect dozens of other gravitational wave signals. Third-generation ground-based interferometers (Einstein Telescope and Cosmic Explorer) and spaaace-based detectors (such as LISA) are being researched and planned to enter into function in the second half of the next decade. If successful, these experiments will allow the detection of thousands of signals coming from an ever-increasing range of cosmological sources. In the meantime, second-generation interferometers are approaching the conclusion of ambitious upgrades started with the end of the third observing run “O3” in march 2020. The work of this thesis revolves around the planning and the commissioning of the “Advanced Virgo plus” upgrade project, which aims to increase the detector’s sensitivity by a factor of two, allowing a ten times higher detection rate than the previous configuration. In particular, the main topic is the update of the interferometer longitudinal sensing and control scheme required by the upgrade in the detector’s optical configuration. The design and simulation of the new control scheme catried out in constant collaboration with the “Interferometer Sensing and Control” team, started minutes before the actual implementation of the upgrades. Following that, I participated in the full-time commissioning of the upgraded configuration, which started in January 2021 and is currently ongoing. We will first explain the new interferometer configuration, then go into the details of the lock-acquisition procedure, presenting the results of the related simulation studies and the commissioning. A particular focus will also be given to the simulations of the interferometer’s state at the end of the lock acquisition, called “steady-state”. In addition to the study and implementation of the current lock-acquisition procedure, the thesis will present simulation activities to study an alternative lock-acquisition technique that has not yet been implemented.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第25114号 / 理博第5021号 / 新制||理||1716(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 田中 貴浩, 教授 向山 信治, 教授 橋本 幸士 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Nous analysons des bulles d'espace-temps d'épaisseur finie en relativité générale. Les conditions d'énergie sont utilisées afin d'obtenir un ensemble de critères permettant de restreindre la structure du bord de la bulle. Dans le cas des bulles statiques et à symétrie sphérique, nous obtenons quatre inégalités différentielles équivalentes aux trois conditions d'énergie les plus communes. Nous montrons qu'elles sont équivalentes à un ensemble de deux inégalités différentielles simples lorsque le potentiel gravitationnel effectif a une forme particulière. Nous paramétrons alors l'espace-temps de manière à rendre la vérification de ces inégalités plus simple lorsqu'il sera question de bulles d'espace-temps. Nous traitons en particulier quatre formes de bulles, toutes caractérisées par un extérieur de type Schwarzschild de Sitter. Nous montrons que notre méthode donne les bons résultats lorsque la limite où l'épaisseur de la bulle tend vers zéro est prise. Nous terminons par un traitement succinct du problème d'une onde gravitationnelle se propageant dans un nuage de bulles d'espace-temps. / We analyze space-time bubbles of finite thickness in general relativity. We use the energy conditions to restrict their structures. In the case of static, spherically symmetric bubbles, we get a set of four differential inequalities. If the effective gravitational potential is taken of a particular form, we show that they can be further reduced to a set of two differential inequalities. We then parameterize the bubble's wall in a particular way, simplifying the inequalities, and easing the application of boundary conditions on our solutions. We then treat four different cases of bubbles that all have a Schwarzschild de Sitter exterior. We show that in the limit where the thickness of the bubble's wall goes to zero, we recover the standard results. Lastly, we treat gravitational waves propagating in a dilute gas of non-interacting space-time bubbles.

A existência de ondas gravitacionais foi confirmada indiretamente pela observação astronômica de pulsares binários. Detectores de ondas gravitacionais tem sido desenvolvidos desde o trabalho pioneiro de Weber nos anos 60. Esforços estão sendo realizados no sentido de aumentar a sensibilidade dos detectores e realizar uma detecção direta, que ainda não foi confirmada. O Grupo GRAVITON está aperfeiçoando e melhorando a sensibilidade de um detector de ondas gravitacionais que se encontra no Laboratório de Estado Sólido e Baixas Temperaturas do Instituto de Física da Universidade de São Paulo (LESBT/IFUSP), na cidade de São Paulo com apoio da FAPESP (processo 2006/56041-3). Esse detector, denominado MARIO SCHENBERG, é composto por uma massa ressonante esférica de CuAl(6%) com 65 cm de diâmetro, com aproximadamente 1150 kg, que deverá atingir a sensibilidade h ~ 10-22 em uma banda passante de 50 Hz, em torno de 3200 Hz, quando estiver operando a temperaturas da ordem de 0,05 K. Atualmente o detector já tem toda a sua infraestrutura criogênica montada e testada para resfriamentos a 4 K e toda a suspensão da esfera bem como todo o sistema de filtragem mecânica construídos e montados. Já foram realizadas as primeiras corridas comissionadas em 2006, 2007 e 2008, quando foram realizados vários diagnósticos sobre o sistema e desde então vem sendo desenvolvidos os transdutores para colocar o detector novamente em operação com melhor sensibilidade. Paralelamente, foram realizadas melhorias no próprio detector em razão dos diagnósticos realizados. O trabalho aqui apresentado está associado ao projeto acima. O autor desenvolveu atividades associadas à construção e desenvolvimentos do detector, que podem ser divididas em três partes principais: na parte mecânica, foi desenvolvido, instalado e testado um novo sistema de isolamento vibracional da suspensão da esfera; na parte criogênica foram feitas novas conexões térmicas, cálculos de gastos de hélio líquido e feitos desenvolvimentos para o funcionamento do refrigerador por diluição; e na parte eletrônica foi feita a instalação da eletrônica responsável pela transdução do sinal, além do desenvolvimento de um novo par de antenas de microfita. / The existence of gravitational waves has been confirmed indirectly by astronomical observation of binary pulsars. Gravitational wave detectors have been developed since the pioneering work of Weber in the 60s. Efforts are being made to increase the sensitivity of the detectors and perform a direct detection, wich has not been confirmed yet. The GRAVITON Group is enhancing and improving the sensitivity of a gravitational wave detector which is at the Laboratório de Estado Sólido e Baixas Temperaturas of the Instituto de Física of the Universidade de São Paulo (LESBT / IFUSP), in São Paulo city and is supported by FAPESP (processo 2006/56041-3). This detector, called MARIO SCHENBERG, consists of a spherical resonant mass of CuAl (6%) with 65 cm in diameter, and approximately 1150 kg, which should reach the sensitivity of h ~ 10-22 in a bandwidth of 50 Hz around 3200 Hz, when operating at temperatures of 0.05 K. Currently the detector already has all its infrastructure assembled and tested for cryogenic cooling down to 4 K and the whole suspension of the sphere as well as all mechanical isolation system constructed and assembled. Commissioning runs have already been done in 2006, 2007 and 2008, when several diagnoses on the system were performed and since then there have been many developments on the transducers to put back the detector into operation with improved sensitivity. At the same time, improvements have been made within the detector itself due to the diagnoses. The work presented here is associated with the above project. The author has developed activities and developments associated with the detector construction, which can be divided into three main parts: the mechanical part, in which a new system of vibration isolation was designed for the sphere suspension, installed and tested; the cryogenic part, in which new connections and thermal calculations of liquid helium boil-off rate were made as well as other developments for the operation of a dilution refrigerator; and the electronic part, in which the installation of the electronic signal responsable for the transduction was made, besides the development of a new pair of micro-strip antenna.

Nous analysons des bulles d'espace-temps d'épaisseur finie en relativité générale. Les conditions d'énergie sont utilisées afin d'obtenir un ensemble de critères permettant de restreindre la structure du bord de la bulle. Dans le cas des bulles statiques et à symétrie sphérique, nous obtenons quatre inégalités différentielles équivalentes aux trois conditions d'énergie les plus communes. Nous montrons qu'elles sont équivalentes à un ensemble de deux inégalités différentielles simples lorsque le potentiel gravitationnel effectif a une forme particulière. Nous paramétrons alors l'espace-temps de manière à rendre la vérification de ces inégalités plus simple lorsqu'il sera question de bulles d'espace-temps. Nous traitons en particulier quatre formes de bulles, toutes caractérisées par un extérieur de type Schwarzschild de Sitter. Nous montrons que notre méthode donne les bons résultats lorsque la limite où l'épaisseur de la bulle tend vers zéro est prise. Nous terminons par un traitement succinct du problème d'une onde gravitationnelle se propageant dans un nuage de bulles d'espace-temps. / We analyze space-time bubbles of finite thickness in general relativity. We use the energy conditions to restrict their structures. In the case of static, spherically symmetric bubbles, we get a set of four differential inequalities. If the effective gravitational potential is taken of a particular form, we show that they can be further reduced to a set of two differential inequalities. We then parameterize the bubble's wall in a particular way, simplifying the inequalities, and easing the application of boundary conditions on our solutions. We then treat four different cases of bubbles that all have a Schwarzschild de Sitter exterior. We show that in the limit where the thickness of the bubble's wall goes to zero, we recover the standard results. Lastly, we treat gravitational waves propagating in a dilute gas of non-interacting space-time bubbles.

This thesis presents the research done towards the development of the final mirror suspension stage for the high power test facility at AIGO, Western Australia. One of the goals of the facility is to test advanced suspension methods that may be useful in future gravitational wave detectors. An in depth study of current mirror suspension techniques is presented and areas of possible improvement are highlighted. The extension of an existing suspension modelling toolkit written in Mathematica is also presented, where added functions allow one to include the violin modes of a suspension into their analysis. Through this tool, new suspension geometries boasting a lower number of violin modes with lower Q factors where developed. The orthogonal ribbon suspension and the thin tube suspension boast a lower number of lower Q violin modes compared to typical ribbon suspensions. For the latter, a reduction in the number of violin modes below 5kHz down to 5 and peak thermal noise amplitude by approximately 30dB is predicted. Presented also is the affect that such suspension geometries have on pendulum mode dilution factor and overall suspension thermal noise. It is seen that the violin mode improvement comes at a cost of a small increase in thermal noise above approximately 50Hz. A theoretical analysis of the AIGO cavity locking control scheme is also given. Issues of sensor noise and dynamic range are considered to produce a possible hierarchical locking method that would be compatible with advanced detectors. The resulting actuator force range requirements for AIGO at each actuation location on the vibration isolation system are given. Requirements of local controls before achieving cavity lock are also discussed. Finally, the suspension of a dummy sapphire mirror using removable modular niobium ribbons is presented. The design and performance of an electrostatic actuator and sensor for suspended mirror control is given. Initial experimental results of positioning and control of the final stage suspension through a digital interface is also included.

Advanced Laser Interferometric Gravitational Wave Detectors, based on current infrastructure (in particular, the Advanced LIGO detectors), are being planned to significantly increase the sensitivity to gravitational wave strain in the near future. To upgrade the existing detectors requests implementing very high optical power, as well as very high circulating power in the arm cavities; these measures will increase the sensitivity at the shot noise floor by one order of magnitude. However, such extremely high power circulation in the cavities will cause optical distortions in the test masses. Thermal distortions arise from the optical power absorption by defects or inhomogeneities in test masses, resulting in wavefront deformations, which have important consequences for the power buildup of the Radio-Frequency (RF) sidebands in the recycling cavities, thus degrading the performance of the detectors. The degree of this sensitivity degradation in the shot noise floor, due to optical distortions induced by defects or inhomogeneities (i.e. imperfections) in test masses in Advanced Laser Interferometric Gravitational-wave Detectors, is dependent on the test mass optical quality; while the sensitivity degradation in the thermal noise floor is dependent on the test mass mechanical properties. For this reason, it is compulsory to use high optical and mechanical quality test mass materials in the advanced interferometer detectors. Fused silica has been used for test masses in detectors, while sapphire has been planned to be used for test mass substrates in the proposed Large-scale Cryogenic Gravitational-wave Telescope (LCGT) project. Other materials, such as calcium fluoride (CaF2), are also attractive, especially for cryogenic detectors. However, for the state-of-theAbstract II art facilities, it is difficult to manufacture very uniform, defect-free, inhomogeneity-free, high-quality, and large-size samples. Thus, the qualities of sapphire and calcium fluoride single crystal samples were investigated and evaluated, to ensure that they have suitable properties for use in interferometer detectors, i.e. with an adequately low level of imperfections, but also with high mechanical quality factor (Q-factor). This thesis describes research done in the endeavour to investigate bulk defects or inhomogeneities in test masses, as well as their induced thermal distortions, which appear at a high optical power in Laser Interferometric Gravitational-wave Detectors. An Automatic Rayleigh Scattering Mapping System (ARSMS) to examine the optical property of large-size test masses is described. This ARSMS enables quantitative high-resolution 3D mapping of defects or inhomogeneities in optical materials. The measured 3D defect distribution mapping of optical materials can assist in the design of suitable configurations of test masses in high optical power interferometers. In addition, a very sensitive Hartmann wavefront sensor was used to actively monitor the thermal distortions due to bulk and coating absorption in test masses. A very strong thermal distortion in these test masses was observed in the Gingin facility, demonstrating that thermal distortions could be a critical issue in advanced interferometer detectors. A negative thermo-optical coefficient material, to be used in a thermal distortion compensation method, was investigated for the compensation of very localised distortions due to imperfections. This thesis also includes experimental and theoretical studies of the scattering, absorption, and birefringence mechanisms, thermal distortion effects, and optimal compensation methods for test masses.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-10-16T18:43:09Z No. of bitstreams: 1 GILVAN BONFIM E SOUZA – DISSERTAÇÃO (PPGFísica) 2017.pdf: 376396 bytes, checksum: 2125734f38cbbf4b7cf62d62515ca94c (MD5) / Made available in DSpace on 2018-10-16T18:43:09Z (GMT). No. of bitstreams: 1 GILVAN BONFIM E SOUZA – DISSERTAÇÃO (PPGFísica) 2017.pdf: 376396 bytes, checksum: 2125734f38cbbf4b7cf62d62515ca94c (MD5) Previous issue date: 2017-02 / Nesta dissertação calculamos alguns limites fenomeno lógicos para a eletrodinâmica e gravitação massiva e maltas ordens derivativas, supondo que é possível ter um processo astrofísico que gere simultaneamente ondas gravitacionais e eletromagnéticas. Apresentamos operadores de altas ordens derivativas que viola a invariância de Lorentz, seguindo a abordagem de Myers-Pospelov para descrição de ondas gravitacionais massivas e eletromagnéticas. Calculamos as equações de movimento desses modelos, suas relações de dispersão e as velocidades. Os parâmetros que controlam a violação no setor gravitacional Ƹg e eletromagnético Ƹy, são obtidos por duas abordagens diferentes: o atraso temporal e diferença de velocidades dos fótons e grávitons. Estes parâmetros dependem das suas respectivas escalas de massa pela qual os efeitos da violação de Lorentz se tornam relevantes, setor eletromagnético dado por M e o setor gravitacional dado M1. A razão entre os parâmetros Ƹg e Ƹy é de interesse do ponto de vista fenomenológicos e M ˃ M1. Determinamos também a diferença entre as velocidades dos fótons e grávitons, e como resultado, obtemos compatível com os resultados apresentados anteriormente na literatura. / In this work,we compute some phenomenological bounds for the electromagnetic and massive gravitational high-derivative extensions supposing that it is possible to have an astrophysical process that generates simultaneously gravitational and electromagnetic waves. We present a Lorentz-violating LIV higher-order derivative, following the Myers- Pospelov approach, to electro dynamics and massive gravitation alwaves. We compute the corrected equation of motion of these models, their dispersion relations and the velocities. The LIV parameters for the gravitational Ƹg and electromagnetic sector Ƹy respectively were also obtained for two different approaches time delay of lightand the difference of graviton and photon velocities. These LIV parameters depend on the masss cales where the LIV-terms be come relevant, M for the electromagnetic sectorand M1 for the gravitational one. The relation between the parameters Ƹg and Ƹy is of interest from the phenomenological point of view if M ˃ M1. We determine the diference betweent heve-locities of the photon and the graviton was calculated and our result, v􀀀�vg .0:62 10􀀀�17, is compatible with the results already presented in the literature.

A existência de ondas gravitacionais foi confirmada indiretamente pela observação astronômica de pulsares binários. Detectores de ondas gravitacionais tem sido desenvolvidos desde o trabalho pioneiro de Weber nos anos 60. Esforços estão sendo realizados no sentido de aumentar a sensibilidade dos detectores e realizar uma detecção direta, que ainda não foi confirmada. O Grupo GRAVITON está aperfeiçoando e melhorando a sensibilidade de um detector de ondas gravitacionais que se encontra no Laboratório de Estado Sólido e Baixas Temperaturas do Instituto de Física da Universidade de São Paulo (LESBT/IFUSP), na cidade de São Paulo com apoio da FAPESP (processo 2006/56041-3). Esse detector, denominado MARIO SCHENBERG, é composto por uma massa ressonante esférica de CuAl(6%) com 65 cm de diâmetro, com aproximadamente 1150 kg, que deverá atingir a sensibilidade h ~ 10-22 em uma banda passante de 50 Hz, em torno de 3200 Hz, quando estiver operando a temperaturas da ordem de 0,05 K. Atualmente o detector já tem toda a sua infraestrutura criogênica montada e testada para resfriamentos a 4 K e toda a suspensão da esfera bem como todo o sistema de filtragem mecânica construídos e montados. Já foram realizadas as primeiras corridas comissionadas em 2006, 2007 e 2008, quando foram realizados vários diagnósticos sobre o sistema e desde então vem sendo desenvolvidos os transdutores para colocar o detector novamente em operação com melhor sensibilidade. Paralelamente, foram realizadas melhorias no próprio detector em razão dos diagnósticos realizados. O trabalho aqui apresentado está associado ao projeto acima. O autor desenvolveu atividades associadas à construção e desenvolvimentos do detector, que podem ser divididas em três partes principais: na parte mecânica, foi desenvolvido, instalado e testado um novo sistema de isolamento vibracional da suspensão da esfera; na parte criogênica foram feitas novas conexões térmicas, cálculos de gastos de hélio líquido e feitos desenvolvimentos para o funcionamento do refrigerador por diluição; e na parte eletrônica foi feita a instalação da eletrônica responsável pela transdução do sinal, além do desenvolvimento de um novo par de antenas de microfita. / The existence of gravitational waves has been confirmed indirectly by astronomical observation of binary pulsars. Gravitational wave detectors have been developed since the pioneering work of Weber in the 60s. Efforts are being made to increase the sensitivity of the detectors and perform a direct detection, wich has not been confirmed yet. The GRAVITON Group is enhancing and improving the sensitivity of a gravitational wave detector which is at the Laboratório de Estado Sólido e Baixas Temperaturas of the Instituto de Física of the Universidade de São Paulo (LESBT / IFUSP), in São Paulo city and is supported by FAPESP (processo 2006/56041-3). This detector, called MARIO SCHENBERG, consists of a spherical resonant mass of CuAl (6%) with 65 cm in diameter, and approximately 1150 kg, which should reach the sensitivity of h ~ 10-22 in a bandwidth of 50 Hz around 3200 Hz, when operating at temperatures of 0.05 K. Currently the detector already has all its infrastructure assembled and tested for cryogenic cooling down to 4 K and the whole suspension of the sphere as well as all mechanical isolation system constructed and assembled. Commissioning runs have already been done in 2006, 2007 and 2008, when several diagnoses on the system were performed and since then there have been many developments on the transducers to put back the detector into operation with improved sensitivity. At the same time, improvements have been made within the detector itself due to the diagnoses. The work presented here is associated with the above project. The author has developed activities and developments associated with the detector construction, which can be divided into three main parts: the mechanical part, in which a new system of vibration isolation was designed for the sphere suspension, installed and tested; the cryogenic part, in which new connections and thermal calculations of liquid helium boil-off rate were made as well as other developments for the operation of a dilution refrigerator; and the electronic part, in which the installation of the electronic signal responsable for the transduction was made, besides the development of a new pair of micro-strip antenna.

Gravitation is the dominant influence in most astrophysical interactions. Weak-field interactions have been extensively studied, but the strong-field regime remains largely unexplored. Gravitational waves (GWs) are an excellent means of accessing strong-field regions. We investigate what we can learn about both astrophysics and gravitation from strong-field tests and, in particular, GWs; we focus upon extreme-mass-ratio (EMR) systems where a small body orbits a much more massive one. EMR bursts, a particular class of GW signals, could be used to determine the properties of massive black holes (MBHs). They could be detectable with a space-borne interferometer from many nearby galaxies, as well as the Galactic centre. Bursts could provide insightful constraints on the MBHs' parameters. These could elucidate the formation history of the MBHs and, by association, their host galaxies. The Galactic centre is the most promising source. Its event rate is determined by the stellar distribution surrounding the MBH; the rate is not high, but we still expect to gain useful astronomical information from bursts. Strong-field tests may reveal deviations from general relativity (GR). We calculate modifications that could be observed assuming metric f(R)-gravity as an effective alternative theory. Gravitational radiation is modified, as are planetary precession rates. Both give a means of testing GR. However, existing laboratory measurements already place tighter constraints on f(R)-gravity, unless there exists a screening effect, such as the chameleon mechanism, which suppresses modifications on small scales. To make precision measurements of astrophysical systems or place exacting bounds on deviations from GR, we must have accurate GW templates. Transient resonances are currently not included in the prescription for generating EMR inspiral waveforms. Their effects can be estimated from asymptotic expansions of the evolving orbital parameters. The quantitative impact on parameter estimation has yet to be calculated, but it appears that it shall be necessary to incorporate resonances when creating inspiral waveforms.