Cryogenic interferometry for 3rd generation gravitational wave detectors

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.