Equipment in support of Investigations in Gravitational Radiation

爱因斯坦的广义相对论（GR）预测，强引力场中的动力系统将以引力辐射的形式释放出大量的能量。引力波是时空结构中的涟漪，以光速从其源头传播，携带着关于其发射的物理过程的信息，这是无法通过其他方式获得的。它们是来自宇宙最深处的最难以捉摸的信号之一。全球的干涉探测器网络包括德国-英国GEO 600、法国-意大利Virgo、美国激光干涉仪引力波天文台（LIGO），并正在加强一个正在建造的新探测器--日本的KAGRA。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我们能够在大部分天空中连续采集数据，对广泛的来源和现象具有敏感性。来自GEO，LIGO和Virgo的数据已经增加了我们对天文现象的理解。在154次伽马射线爆发时对引力波的搜索已经允许了有史以来最好的排除距离，并为银河系外的软伽马中继源提供了证据。在最近的运行中，双黑洞的距离达到300 Mpc，速率上限现在非常接近一些天体物理模型的预期。对船帆座脉冲星引力波的研究为辐射强度设定了一个上限，这个上限明显低于从观测到的脉冲星自旋下降速率所预期的上限，相当于星星椭圆率的千分之一。本设备提案将支持由我们的综合赠款ST/L000946/1支助的探测器研究和开发实验方案。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。我们主要负责aLIGO中的二氧化硅悬浮液，以及aLIGO探测器的增强和升级，包括用于低热噪声的镜面涂层，硅衬底，低温悬浮液和改进的干涉仪拓扑结构以对抗量子噪声。

Einstein's General Theory of Relativity (GR) predicts that dynamical systems in strong gravitational fields will release vast amounts of energy in the form of gravitational radiation. Gravitational waves are ripples in the fabric of spacetime and travel from their sources at the speed of light, carrying information about physical processes responsible for their emission, obtainable in no other way. 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 sensitivity levels where detection is expected within a few years.The worldwide network of interferometric detectors includes the German-UK GEO600, the French-Italian Virgo, the American Laser Interferometer Gravitational-Wave Observatory (LIGO) and is being enhanced with a new detector under construction - KAGRA 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 enables continuous data acquisition, with sensitivity to a wide range of sources and phenomena, over most of the sky.Data from GEO, LIGO and Virgo, have already increased our understanding of astronomical phenomena. Search for gravitational waves at the times of 154 gamma-ray bursts has allowed the best ever exclusion distances and provided evidence for extra-Galactic sources of soft-gamma repeaters. The distance reach for binary black holes in the most recent runs is 300 Mpc and the rate upper limits are now very close to that expected in some of the astrophysical models. The search for gravitational waves from the Vela pulsar has set an upper bound on the strength of radiation that is significantly below that expected from the observed spin down rate of the pulsar, corresponding to a limit on the star's ellipticity of a part in a thousand. This proposal for equipment will support the experimental programme of detector research and development supported by our Consolidated Grant ST/L000946/1. 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. We have major responsibilities for the silica suspensions in aLIGO, and in the development of enhancements and upgrades to the aLIGO detectors, in the areas of mirror coatings for low thermal noise, silicon substrates, cryogenic suspensions and improved interferometer topologies to combat quantum noise.