Stanford Program in Support of LIGO - Seismic Isolation and Controls

在现代望远镜中，仪器的价值很大程度上取决于安装和跟踪的稳定性。对于激光干涉仪引力波天文台（LIGO）来说尤其如此——悬挂和隔离的价值是至关重要的，因为镜子必须悬挂在晃动的地面之上。斯坦福大学的工作重点是设计和实现支撑4公里长的LIGO干涉仪光学系统的底座。目前的设备擅长将LIGO与典型的地面震动隔离开来；这笔拨款将资助几项相关工作，以改善LIGO探测器在大地震干扰期间的稳健运行，并将资助开发新技术，以隔离未来的低温探测器的光学。为了改善现有观测站的占空比，这笔拨款支持通过结合计算流体动力学、风洞测试和观测站现场测量来开发低成本的风障和改进的控制算法来减轻风暴对探测器的影响。这笔拨款还支持开发和测试新的控制方案，以帮助改善探测器在大型远震期间的操作。最近的研究表明，在地震期间，近90%的低频地面运动对探测器中的所有光学元件都是共同的。新的研究将积极协调所有平台的运动，同时最小化天文台4公里长度上的共模驱动和差模运动。控制力的大幅降低和微分漂移的改善有望显著提高检测器的整体鲁棒性。斯坦福大学运营着10米真空系统和原型隔离系统的工程测试设施，在这里进行引力波开发的综合硬件和软件开发。这笔赠款资助在该设施进行的观测站隔震研究，这些研究目前处于早期规划阶段。未来的探测器有望使用冷却光学来减少反射镜的热驱动（布朗）噪声。然而，这些反射镜将有超过1兆瓦的激光功率照射在它们上面，因此在低温下运行它们需要能够持续地去除大量的热能。这样做的技术将在原型隔离平台上进行测试，以便可以同时开发和测试冷却和振动控制的要求。

In modern telescopes, much of the instrument's value lies in the stability of the mount and tracking. This is especially true for the Laser Interferometer Gravitational-wave Observatory (LIGO) - the value of the suspension and isolation is paramount because the mirrors must be suspended above the shaking ground. The work at Stanford is focused on the design and implementation of the mount that supports the optics for the 4-km long LIGO interferometer. The current facilities excel at isolating LIGO from the typical shaking of the ground; this grant will fund several related efforts to improve the robust operation of the LIGO detectors during large seismic disturbances, and it will also fund development of new techniques to isolate the optics of future, cryogenic detectors.To improve the duty cycle of the existing observatories, this grant supports work to mitigate the impact of wind storms on the detectors by combining computational fluid dynamics, wind tunnel tests, and observatory field measurements to develop low-cost wind barriers and improved control algorithms. The grant also supports development and testing of novel control schemes to help improve the operation of the detector during large, teleseismic earthquakes. Recent work has shown that nearly 90% of the low frequency ground motion during an earthquake is common to all the optics in the detector. The new research will actively coordinate the motion of all the platforms to simultaneously minimize the common-mode drives and the differential-mode motion over the 4-km length of the observatory. The large reduction in control force, and the improvement in differential excursions is expected to significantly improve the overall robustness of the detector. Stanford University operates the Engineering Test Facility, a 10-meter vacuum system with a prototype isolation system, where integrated hardware and software development for gravitational wave development is conducted. This grant funds research in this facility for seismic isolation of observatories which are now in the early planning stages. Future detectors are expected to use cooled optics to reduce the thermally driven (Brownian) noise of the mirrors. However, these mirrors will have more than a megawatt of laser power incident upon them, so running them at cryogenic temperatures requires the ability to continuous remove significant thermal energy. Techniques to do this will be tested on the prototype isolation platform so that the requirements for cooling and vibration control can be developed and tested simultaneously.