Thermal Noise in Test Masses and Suspensions for Gravitational Wave Interferometers

根据涨落耗散定理，热噪声产生于任何耗散机械能的机制。这意味着一个引力波干涉仪测试质量和它的悬架就会工作得越好，耗散水平越低。锡拉丘兹大学的研究小组将对各种测试质量和悬架设计进行研究，并通过它们的耗散水平来表征它们。一种方法是测量系统中各种机械共振的质量因子。锡拉丘兹大学的研究小组最近开发了一种新方法，在释放稳定的压力后，仔细测量系统的反应。这两种方法都将用于寻找建立和暂停LIGO测试质量的最佳方法。为了成功地搜寻引力波，探测器必须不受干扰影响，以免模仿或掩盖微弱的引力波信号。热噪声，也称为布朗运动，是最需要减少的噪声源之一。锡拉丘兹大学小组的研究计划的目的是了解引力波干涉探测器（如LIGO项目）的热噪声来源，并因此学习最小化其强度的方法。除了提高LIGO和其他引力波探测器的性能这一主要目标外，这项工作还可能促进人们对非晶体固体结构的理解，比如用来制造测试质量的熔融二氧化硅。

According to the Fluctuation-Dissipation Theorem, thermal noise arises from any mechanism that dissipates mechanical energy. This means that a gravitational wave interferometer test mass and its suspension will work better, the lower is the level of dissipation. The Syracuse group will carry out studies of various test mass and suspension designs, characterizing them by their dissipation levels. One means of doing this is to measure the quality factors of the various mechanical resonances in the system. A novel method, newly developed by the Syracuse group, involves careful measurement of the response of the system after a steady stress has been released. Both methods will be employed in the search for the best ways to build and suspend test masses for LIGO. In order for the search for gravitational waves to succeed, it is necessary that detectors be free from disturbing influences that can mimic or mask the weak gravitational wave signal. Thermal noise, also known as Brownian motion, is among the noise sources most in need of reduction. The aim of the research program of the Syracuse University group is to understand the sources of thermal noise in interferometric detectors of gravitational waves (such as those of the LIGO Project), and to thereby learn ways of minimizing its strength. In addition to its main goal of improving the performance of LIGO and other gravitational wave detectors, this work may stimulate progress in understanding the structure of noncrystalline solids, such as the fused silica from which test masses are made.