Low Noise Suspensions and Readout Systems for Improving Advanced LIGO

这是弗拉基米尔·布拉金斯基的莫斯科国立大学(MSU)团队和激光干涉仪引力波天文台(LIGO)实验室合作的研究项目。它重点介绍了高级LIGO正在考虑的两种增强措施：将晶体硅用于干涉仪反射镜以降低热噪声，以及使用量子测量技术，使灵敏度超过由于量子(散粒)噪声而造成的当前限制。众所周知，晶体硅具有优异的机械性能，在120K附近的热膨胀最小。在这一点上操作将使热噪声降至最低。然而，对于大规模应用来说，许多方面还没有被很好地理解。在这笔资助下，我们探索了在120K下工作的硅测试质量悬浮体的硅带制造技术，测量了硅带悬浮体中的损耗，并找到了最小化硅悬浮体中的损耗和热噪声的方法。我们研究了纯高欧姆结晶硅和其他可能的候选材料的光学损耗和其他测量不佳的热、机械和光学性能，这些材料可以用于从室温到液氮温度的测试质量。最后分析了用于硅测试质量块的晶态涂层中的噪声来源。高级LIGO灵敏度的另一个主要限制将是量子(散粒)噪声。我们还继续研究激光引力波探测器的新拓扑和测量方案，与增强的高级LIGO和更高级的LIGO相关，并允许我们抑制量子噪声并放宽对循环光功率的要求。这项工作的结果产生了一些影响。最直接的是，开发的技术可以用来使引力波探测器更灵敏，从而有助于获得更多关于引起引力波的天体物理现象的信息。了解产生引力波的不同寻常的条件有助于我们理解塑造我们宇宙的剧烈过程，这些过程令学生和公众兴奋和鼓舞。更广泛地说，根据这项研究开发的相同技术可以在科学和工程中的许多精密测量应用中使用。这些措施包括减少精确频率参考标准中的噪音以产生更准确的时钟，使量子密码学和量子计算更加可行，改进对空间和物质的基本假设的测试，以及……最后，这项工作的一个主要目标是促进俄罗斯和美国科学家在和平研究方面更紧密的合作。这促进了这两个超级大国科学界之间的更好理解。

This is a collaborative research program between Vladimir Braginsky's Moscow State University (MSU) group and the Laser Interferometer Gravitational-Wave Observatory (LIGO) Laboratory. It focuses on two types of enhancements under consideration for Advanced LIGO: the use of crystalline silicon for the interferometer mirrors to reduce thermal noise, and quantum measurement techniques that can give sensitivities beyond the current limits due to quantum (shot) noise. Crystalline silicon is known to have excellent mechanical properties and has a minimum in its thermal expansion near 120 K. Operation at this point would minimize thermal noise. However, many aspects are not yet well enough understood for large scale application. Under this grant, we explore techniques for fabricating silicon ribbons for a silicon test mass suspension operating at 120 K, measure dissipation in silicon ribbon suspensions, and to find ways of minimization dissipation and thermal noise in the silicon suspensions. We investigate optical losses and other poorly measured thermal, mechanical and optical properties of pure high-ohmic crystalline silicon and other possible candidate materials for test masses from room to liquid nitrogen temperatures. Finally we analyze sources of noise in crystalline coatings applied to silicon test masses. The other main limitation to the sensitivity of Advanced LIGO will be quantum (shot) noise. We also continue the investigation of new topologies and measurement schemes for laser gravitational wave detectors, relevant to both Enhanced Advanced LIGO and beyond, and allowing us to suppress quantum noise and to relax requirements for the circulating optical power. The results of this work have a number of impacts. The most direct is that the techniques developed can be used to make gravitational wave detectors more sensitive, and thus help derive more information about the astrophysical phenomena that cause gravitational waves. Understanding the unusual conditions that create gravitational waves improves our understanding of violent processes that shape our universe exciting and inspiring students and the public. More broadly, the same techniques which are developed under this research can be used in a number of precision measurement applications in science and engineering. These include reducing noise in precison frequency reference standards to produce more accurate clocks, making quantum cryptography and quantum computing more feasible, improved tests of fundamental assumptions about space and matter, and ... finally, a major goal of this work is to foster closer collaboration on peaceful research between Russian and US scientists. This promotes better understanding between the scientific communities in these two super-powers.