Title: Reducing suspension control noise with interferometric sensors -- an experimental concept Show Chinese title

Title: 用干涉传感器降低悬架控制噪声——一种实验性概念

Abstract: One of the limiting noise sources of ground-based gravitational wave detectors at frequencies below 30 Hz is control-induced displacement noise. Compact laser interferometric sensors are a prime candidate for improved local displacement sensing. In this paper we present the design of an experiment that aims to demonstrate the advantages of interferometric sensors over shadow sensors. We focus on the compact balanced readout interferometer (COBRI) - a sensor currently in development that is based on deep frequency modulation. We mount COBRIs on two HAM Relay Triple Suspension (HRTS) systems that suspend two mirrors forming an optical cavity. By measuring the length stability of this cavity relative to a stable reference we aim to probe the direct motion reduction when using COBRIs for active damping and we aim to investigate their behavior and auxiliary functions, such as absolute ranging, in the context of the 6 degree-of-freedom controls of the suspensions. Here we describe the design of the experiment and simulations of the achievable noise levels that were obtained using mechanical models of the HRTS suspensions. We discuss all relevant noise sources, the modeled influence of the interferometric sensor damping and the current limitations and necessary improvements of our testing facility in terms of seismic pre-isolation to achieve a shadow sensor limited noise at around 5 Hz, where, according to our simulations, we can demonstrate superior performance for COBRIs in the longitudinal degree of freedom. Show Chinese abstract

Abstract: 地面引力波探测器在30赫兹以下频率的一个限制性噪声源是控制引起的位移噪声。紧凑型激光干涉传感器是改进局部位移传感的首选方案。在本文中，我们介绍了旨在展示干涉传感器相对于阴影传感器优势的实验设计。我们专注于紧凑型平衡读出干涉仪（COBRI）——一种目前正在开发的基于深度频率调制的传感器。我们将COBRI安装在两个HAM中继三重悬挂（HRTS）系统上，这些系统悬挂着形成光学腔的两个镜子。通过测量该腔相对于稳定参考的长度稳定性，我们旨在探测使用COBRI进行主动阻尼时的直接运动减少，并旨在研究其行为和辅助功能，例如绝对测距，在悬挂系统的6自由度控制背景下。在这里，我们描述了实验的设计以及使用HRTS悬挂的机械模型获得的可实现噪声水平的模拟。我们讨论了所有相关的噪声源，干涉传感器阻尼的建模影响，以及在地震预隔离方面我们测试设施的当前限制和必要的改进，以在大约5赫兹处实现阴影传感器限制的噪声，在此频率下，根据我们的模拟，我们可以展示COBRI在纵向自由度上的优越性能。