Sensors for Low-Frequency Improvements in Advanced LIGO

去年2月，先进的LIGO首次探测到引力波，打开了一扇通往宇宙的新窗口。该合同支持在位于华盛顿州汉福德和洛杉矶利文斯顿的LIGO站点部署新设备的开发。这包括一个高精度惯性倾斜传感器，用于独立于水平加速度测量水平倾斜，这将提高先进的LIGO地震隔离，使干涉仪在恶劣环境条件下稳健运行。倾斜传感器的研究将对地震学和地球物理学等领域产生更广泛的影响，因为它可以在低至10兆赫兹的频率下测量远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和精密实验中具有广泛的应用。该奖项不仅支持先进LIGO设备的开发，而且还有助于维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、研究生和博士后在制造精密机械仪器方面的能力。在LIGO从探测器到天文台的转变过程中，保持高占空比是一个关键的挑战。在首次观测运行期间，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。通过进一步的改进，使它们更小，更敏感，具有干涉读数，将允许它们直接安装在LIGO反射镜悬挂的隔离平台上，从而使反射镜的低频微分运动更强，更直接。此外，它们可能在测量引力波信号频带5-30赫兹的地震倾斜度方面被证明是有用的，可以消除牛顿噪声，这有望限制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.