Capital Equipment in support of 'Investigations in Gravitational Radiation', 2014

爱因斯坦的广义相对论预言，处于强引力场中的动力系统会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，以光速从源头传播，携带着有关引力波发射的物理过程的信息，这是其他任何方式都无法获得的。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探测到的灵敏度水平。干涉探测器的全球网络包括德国-英国的GEO600，法国-意大利的Virgo，美国的激光干涉引力波天文台（LIGO），以及正在建设中的新探测器——日本的KAGRA。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可以实现对大部分天空中各种来源和现象的持续数据采集。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，得到了有史以来最好的排除距离，并为银河系外软伽马中继源的存在提供了证据。在最近的运行中，双黑洞的距离达到了300mpc，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搜索已经为辐射强度设定了一个上限，这个上限大大低于从观测到的脉冲星自旋下降速率所期望的上限，相当于该恒星椭圆率的千分之一的极限。该设备提案将支持由我们的综合拨款ST/L000938/1支持的探测器研究和开发实验计划。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。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开发，以及用于低热噪声的镜面涂层，硅衬底，低温悬浮液和改进干涉仪拓扑以对抗量子噪声的领域。

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/L000938/1. 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.