Cryogenic interferometry for 3rd generation gravitational wave detectors

格拉斯哥大学投资了一项新的干涉测量设备，为第三代引力波探测器开发硬件。第三代引力波探测器是一种超灵敏仪器，可以探测中子星、黑洞和坍塌的超新星在时空中产生的微小涟漪。2015年，先进的LIGO干涉仪首次探测到引力波，这是自20世纪60年代罗恩·德雷弗在格拉斯哥大学的开创性工作以来50年研究的巅峰。这开启了天文学的新纪元，产生了2017年的诺贝尔物理学奖。开发更灵敏的引力波探测器是STFC的一个关键优先事项。第三代探测器的灵敏度将超过高级LIGO探测器一个数量级以上，使它们能够探测到宇宙距离尺度之外的源，并以更高的精度表征局部宇宙中的源。这些天文台可以对恒星质量黑洞合并的完整群体进行编目，研究中子星的内部工作原理，启动GW宇宙学领域，并执行广义相对论的强场测试，以潜在地揭示新的物理。要达到这样的性能水平，需要在低噪声仪器方面取得重大突破。最具变革性的变化将是在低温下操作干涉仪，以减少测试块、光学涂层和悬浮纤维中的布朗热噪声。这将通过将测试质量和悬浮纤维材料从熔融二氧化硅改为硅，并将每个测试质量辐射冷却到123K来实现，在123K，硅的热膨胀系数(CTE)为零，几个技术噪声源被降至最低。几十年来，格拉斯哥一直处于引力波探测器仪器科学的前沿，我们将使用我们新的低温干涉设备开发我们研究所开发的第一个带有低噪声低温光学涂层的单片硅测试质量悬浮液的原型。我们将利用我们在低噪声干涉测量方面的专业知识来证明，这种新硬件的性能优于目前引力波探测器中使用的仪器。这将是第三代低温探测器技术准备情况的关键演示。在博士期间，维多利亚·格雷厄姆将在这种新型测试团的设计和开发中发挥主导作用。她将委托我们的新低温原型，并进行精密干涉测量，以验证其性能。在这个过程中，她将获得精密激光稳定、地震隔离、数字控制和信号处理以及低温方面的技能。这项工作将与斯特拉斯克莱德大学、西苏格兰大学和LIGO科学合作中的许多其他机构的同事合作进行。

The University of Glasgow has invested in a new interferometry facility to develop hardware for third-generation gravitational wave detectors, ultrasensitive instruments that sense minute ripples in space time from merging neutron stars, black holes, and collapsing supernovae. Gravitational waves were first detected by the Advanced LIGO interferometers in 2015, a culmination of 50 years' worth of research dating back to Ron Drever's pioneering work at the University of Glasgow in the 1960s. This launched a new era in astronomy, resulting in the Nobel Prize in Physics in 2017. The development of more sensitive gravitational wave detectors is a key priority of the STFC. The sensitivity of third-generation detectors will surpass that of Advanced LIGO by more than an order of magnitude, allowing them to detect sources out to cosmological distance scales and characterize those in the local universe with improved precision. These observatories can catalogue the complete population of stellar mass black hole mergers, study the inner workings of neutron stars, launch the field of GW cosmology, and perform strong-field tests of general relativity to potentially unveil new physics. Achieving this level of performance will require significant breakthroughs in low noise instrumentation. The most transformative change will be operating the interferometer at cryogenic temperatures to reduce Brownian thermal noise in the test masses, optical coatings, and suspension fibres. This will be implemented by changing the test mass and suspension fibre material from fused silica to silicon and radiatively cooling each test mass to 123 K where the coefficient of thermal expansion (CTE) of silicon is zero and several sources of technical noise are minimized. Glasgow has been at the forefront of instrument science for gravitational wave detectors for decades, and we will use our new cryogenic interferometry facility to develop the first prototype monolithic silicon test mass suspensions with low noise cryogenic optical coatings developed at our institute. We will use our expertise in low noise interferometry to demonstrate that this new hardware outperforms instrumentation used in current gravitational wave detectors. This will be a key demonstration of technical readiness for 3rd generation cryogenic detectors. During her PhD, Victoria Graham will have a leading role in the design and development of this new type of test mass. She will commission our new cryogenic prototype and perform precision interferometric measurements to verify its performance. During the process she will gain skills in precision laser stabilization, seismic isolation, digital controls and signal processing, and cryogenics. This work will be carried out in collaboration with colleagues at the University of Strathclyde, University of the West Scotland, and numerous other institutions within the LIGO scientific collaboration.