LIGO Document P1300051-v1
- This thesis discusses the development of optical read-out techniques, including a simple shadow sensor and a more elaborate compact homodyne interferometer, known as EUCLID. Both of these sensors could be utilised as part of a seismic isolation and suspension system of a ground-based gravitational wave observatory, such as Advanced LIGO.
As part of the University of Birmingham’s commitment to the upgrade of Advanced LIGO, it was responsible for providing a large quantity of sensor and actuator units. This required the development and qualification of the shadow sensor, through to production and testing. While characterising production units, an excess noise issue was uncovered and eventually mitigated; demonstrating that even for a ‘simple’ shadow sensor, ensuring a large quantity of units meet the target sensitivity requirement of 3×10^-10 m Hz-1/2 at 1 Hz, is not a trivial exercise.
Over the duration of this research, I played a key role in the design and fabrication of a novel compact interferometer. The objective of this work was to demonstrate that the interferometric technique offers a significant improvement over the existing shadow sensors and could easily be deployed in current, or future, generations of gravitational wave observatories. Encouraging sensitivities of ≈ 50 pm Hz^-1/2 at 1 Hz, over operating ranges of ≈ 6 mm have been achieved, whilst maintaining ± 1 degree of mirror tilt immunity. In addition, this design overcomes many of the drawbacks traditionally associated with interferometers.
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