Sensors for Low-Frequency Improvements in Advanced LIGO

去年2月，高级LIGO首次探测到引力波，打开了一扇通往宇宙的新窗口。该奖项支持开发将部署在华盛顿州汉福德和洛杉矶利文斯顿的LIGO站点的新设备。这包括一个高精度惯性倾斜传感器，可独立于水平加速度测量水平倾斜，这将改进Advanced LIGO地震隔离，使干涉仪能够在恶劣环境条件下稳健运行。倾斜传感器的研究将在地震学和地球物理学等领域产生更广泛的影响，因为它能够在低至10兆赫的频率下测量远程地震倾斜和无倾斜地面加速度。为这些倾斜传感器开发的高精度角度读数在计量学和精密实验中有广泛的应用。该奖项不仅支持高级LIGO设备的开发，还有助于保持和加强这个桌面重力小组与引力波探测社区的协同活动。重要的是，这项STEM研究将培养本科生、研究生和博士后建造精密机械仪器。在LIGO从探测器到天文台的过渡中，保持高占空比是一个关键挑战。在第一次观测中，大风、微震和地震等环境条件是显著限制占空比的主要原因。这是由于地震仪无法区分低频倾斜和平移，即所谓的倾斜-水平耦合。该小组开发的地面倾斜传感器已被证明可以改善LIGO的低频地震隔离。通过使它们更小、更灵敏地使用干涉读数进行进一步改进，将允许它们直接安装在悬挂LIGO反射镜的隔离平台上，从而使反射镜的低频差分运动获得更大和直接的好处。此外，它们在测量5-30赫兹引力波信号带内的地震倾斜度时可能很有用，可以抵消牛顿噪声，而牛顿噪声预计会限制aLIGO和未来探测器的灵敏度。

Last February, Advanced LIGO detected gravitational waves for the first time, opening a new window to the universe.This award supports the development of new equipment to be deployed at the LIGO sites in Hanford, WA, and Livingston, LA. This consists of a high precision inertial tilt sensor to measure horizontal tilt independently from horizontal acceleration, which will improve Advanced LIGO seismic isolation, enabling robust operation of the interferometer under adverse environmental conditions. Research on tilt sensors will have a broader impact in areas such as seismology and geophysics by enabling measurement of tele-seismic tilts and tilt-free ground acceleration at frequencies as low as 10 mHz. The high precision angle readouts developed for these tilt sensors have a wide variety of applications in metrology and precision experiments. This award not only supports the development of a device for Advanced LIGO, but it also serves to maintain and strengthen synergistic activities of this table-top gravity group with the gravitational wave detection community. Importantly, this STEM research will train undergraduate and graduate students, and postdocs in building precision mechanical instruments.In LIGO's transition from Detector to Observatory, maintaining high duty cycles is a key challenge. Environmental conditions such as high wind, microseism and earthquakes were primarily responsible for significantly limiting the duty cycle during the first observing run. This is due to the inability of seismometers to distinguish between low-frequency tilt and translation, known as tilt-horizontal coupling. The ground-tilt sensors the group has developed have been demonstrated to improve the low-frequency seismic isolation in LIGO. Further improvement by making them smaller and more sensitive with interferometric readouts, would allow them to be mounted directly on the isolated platforms from which the LIGO mirrors are suspended, enabling a stronger and direct benefit to low-frequency differential motion of the mirrors. In addition, they may prove useful in measuring seismic tilts in the gravitational wave-signal band between 5-30 Hz, allowing cancellation of Newtonian noise, which is expected to limit sensitivity of aLIGO and future detectors.