Investigations in gravitational radiation

爱因斯坦的广义相对论预言，处于强引力场中的动力系统将以引力波（GW）的形式释放出大量的能量。这些是时空结构中的涟漪，以光速从它们的源头传播，携带着有关它们发射的物理过程的信息。它们是来自宇宙最深处最难以捉摸的信号之一。旨在探测它们的实验已经进行了几十年，现在已经达到了预期在几年内就能探测到的灵敏度。干涉探测器的全球网络包括美国先进的激光干涉引力波天文台（aLIGO），法国-意大利-荷兰-波兰先进的处女座和德国-英国GEO600，后者正在日本建设的新探测器（KAGRA）得到加强。以前的探测器都达到了接近设计目标的灵敏度，并收集了迄今为止最敏感的数据。不同项目之间的合作使持续的数据采集成为可能，对大部分天空的各种来源和现象都很敏感。对GW源进行建模可以进行更深入的搜索，来自LIGO、Virgo和GEO的数据增加了我们对天文现象的理解。例如，我们建立了精确的模型来描述旋转黑洞双星的动力学，以提高探测效率和参数估计的准确性；开展了致密双星和超新星形成和演化的区分模型的研究；排除了合并中子星双星作为伽马射线暴（GRB） GRB070201的祖先，并表明蟹状星云脉冲星的辐射功率不到1%在GW。我们现在正进入一个新时代，先进的探测器开始了第一阶段的运行，我们预计在几年内，将对GW进行常规观测。aLIGO探测器是基于英国为GEO600开发的准单片二氧化硅悬浮液概念和我们的德国同事在GEO600开发的高功率激光器。AdV探测器还使用了二氧化硅悬浮液技术的一种变体。此外，KAGRA正在建造中投入了来自英国集团的低温粘合技术。由于12年前开始第一次数据采集以来得到的资金支持，这些联盟组织发起并领导了对天文来源的搜索。几个搜索的关键成分（精确的波形模型，优化搜索的数据分析的几何公式，搜索通用爆发的算法，贝叶斯搜索和推理技术）在卡迪夫和格拉斯哥开发。我们提出了一个方案，在分析最新的LIGO/Virgo科学运行数据和GEO600数据的基础上，充分利用来自aLIGO和AdV的数据，同时先进的探测器正在建设中。特别是，我们将完善波形模型，并对合并双星、与grb和超新星同时发射的GW以及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，我们提出必要的检测器研发。探测器的灵敏度主要受限于与反射镜衬底、反射涂层及其悬浮元件相关的热噪声，以及由用于传感的光的量子性质引起的噪声。我们的研究目标是在这些领域进行创新改进，这对于最大化GW天文台的天体物理潜力至关重要。我们主要负责aLIGO的二氧化硅悬浊液，无论是在美国还是在印度可能的第三个aLIGO探测器，以及在低热噪声、硅衬底、室温和低温悬浊液以及改进干涉仪拓扑以对抗量子噪声领域对aLIGO探测器进行增强和升级的开发。

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.