Investigations in Gravitational Radiation

爱因斯坦的广义相对论预言，强引力场中的动力系统将以引力波（GW）的形式发射出大量的能量。这些是时空结构中的涟漪，它们以光速从它们的源头传播，携带着关于导致它们发射的物理过程的信息。它们是来自宇宙最深处的最难以捉摸的信号之一。旨在探测它们的实验已经发展了几十年，现在已经达到了预期在几年内探测到的灵敏度。世界范围内的干涉探测器网络包括美国先进的激光干涉仪引力波天文台（aLIGO），法国-意大利-荷兰-波兰先进的Virgo和德国-英国GEO 600，正在用日本正在建造的新探测器（KAGRA）进行增强。以前的探测器都达到了接近其设计目标的灵敏度，并获得了迄今为止最敏感的数据。不同项目之间的合作使得能够在大部分天空中连续获取数据，对广泛的来源和现象具有敏感性。GW源的建模允许更深入的搜索，来自LIGO，Virgo和GEO的数据增加了我们对天文现象的理解。例如，我们建立了描述旋转黑洞双星动力学的精确模型，以提高探测效率和参数估计的准确性，启动了致密双星和超新星形成和演化的区分模型研究，排除了合并中子星星双星作为伽马射线暴（GRB）GRB 070201的祖先，我们现在进入了一个新的时代，先进的探测器开始他们的第一阶段的操作，并在几年内，我们预计，定期观察GW。aLIGO探测器基于英国为GEO 600开发的准单片二氧化硅悬浮概念和我们的德国同事在GEO 600中开发的高功率激光器。AdV检测器还使用二氧化硅悬浮技术的变体。此外，KAGRA正在建造中，来自英国集团的低温粘合技术投入。由于自12年前首次数据采集运行以来获得的资金支持，该财团集团已经发起并领导了天文源的搜索。几个搜索的关键要素（精确的波形模型，数据分析的几何公式，以优化搜索，算法搜索通用突发，贝叶斯搜索和推理技术）是在卡迪夫和格拉斯哥开发的。我们提出了一个方案，导致充分利用数据从aLIGO和AdV，基于对最新LIGO/Virgo科学运行和GEO 600数据的分析，而先进的探测器正在建设中。特别是，我们将改进波形模型，并对合并双星、与GRB和超新星同时发射的GW以及来自旋转中子星的连续信号进行深入和广泛的参数空间搜索。同时，我们提出了必要的探测器研发。检测器的灵敏度主要受到与反射镜的基板、反射涂层和悬挂元件相关的热噪声的限制，也受到传感中所用光的量子性质所产生的噪声的限制。我们的研究目标是在这些领域进行创新性改进，这对最大限度地发挥GW天文台的天体物理潜力至关重要。我们主要负责aLIGO中的二氧化硅悬浮液，无论是在美国还是在印度的第三个aLIGO探测器，并在低热噪声反射镜涂层，硅衬底，室温和低温悬浮液以及改进干涉仪拓扑结构以对抗量子噪声等领域对aLIGO探测器进行增强和升级。

Einstein's General Relativity predicts that dynamical systems in strong gravitational fields will emit vast amounts of energy in the form of gravitational waves (GW). These are ripples in the very fabric of spacetime that travel from their sources at the speed of light, carrying information about physical processes responsible for their emission. They are among the most elusive signals from the deepest reaches in the Universe. Experiments aimed at detecting them have been in development for several decades, and are now reaching sensitivities where detection is expected within a few years.The worldwide network of interferometric detectors includes the American advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO), the French-Italian-Dutch-Polish advanced Virgo and the German-UK GEO600 that are being enhanced with a new detector (KAGRA) under construction in Japan. The former detectors have all reached sensitivities close to their design goals and have taken the most sensitive data to date. Cooperation amongst different projects has enabled continuous data acquisition, with sensitivity to a wide range of sources and phenomena, over most of the sky. Modelling GW sources has allowed deeper searches and data from LIGO, Virgo, and GEO have increased our understanding of astronomical phenomena. For example, we have built accurate models to describe the dynamics of spinning black hole binaries for improving efficiency of detection and accuracy of parameter estimation, initiated studies on distinguishing models of the formation and evolution of compact binaries and supernovae, ruled out merging neutron star binary as progenitor of the gamma ray burst (GRB) GRB070201, and shown that less than 1% of the Crab pulsar's radiated power is in GW.We are now entering a new era as advanced detectors begin their first phase of operation and within a few years will, we expect, routinely observe GW. The aLIGO detectors are based on the quasi-monolithic silica suspension concept developed in the UK for GEO600 and on the high power lasers developed by our German colleagues in GEO600. The AdV detector also uses a variant of the silica suspension technology. Further, KAGRA is being built with input on cryogenic bonding technology from the UK groups.The consortium groups have initiated and led searches for astronomical sources, thanks to funding support received since first data taking runs began 12 years ago. Key ingredients of several searches (accurate waveforms models, geometric formulation of data analysis to optimise searches, algorithms to search for generic bursts, Bayesian search and inference techniques) were developed at Cardiff and Glasgow.We propose a programme that leads to full exploitation of data from aLIGO and AdV, building on the analysis of data from the most recent LIGO/Virgo science runs and from GEO600 while the advanced detectors were under construction. In particular, we will refine waveform models and carry out deep and wide parameter space searches for coalescing binaries, GW emitted in coincidence with GRBs and supernovae, and continuous signals from rotating neutron stars.In parallel, we propose essential detector R&D. Detector sensitivity is mainly limited by thermal noise associated with the substrates of the mirrors, their reflective coatings, and their suspension elements, as well as by noise resulting from the quantum nature of the light used in sensing. Our research is targeted towards making innovative improvements in these areas, essential to maximize the astrophysical potential of GW observatories. We have major responsibilities for the silica suspensions in aLIGO, both in the US and for a possible 3rd aLIGO detector in India, and in the development of enhancements and upgrades to the aLIGO detectors in the areas of mirror coatings for low thermal noise, silicon substrates, room temperature and cryogenic suspensions and improved interferometer topologies to combat quantum noise.