Breaking the seismic wall: how to improve gravitational wave detectors at low frequency

Cooper, Samuel James ORCID: 0000-0001-8114-3596 (2020). Breaking the seismic wall: how to improve gravitational wave detectors at low frequency. University of Birmingham. Ph.D.

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The era of gravitational-wave astronomy was enabled by the incredible sensitivity of the LIGO and VIRGO detectors. However, they are still plagued by technical noises at frequencies below 30 Hz, driven in part by the limitations of the seismic isolation of the detector. To detect gravitational waves at low frequency, the isolation performance must be improved to reduce these technical noises.

To improve the performance of seismic isolation systems, I have developed HoQI a new interferometrically sensor, that can be applied to both the isolation tables and suspensions. HoQI has a resolution a factor 1000 higher than sensors currently used in LIGO and I have quantified the level of non-linearity present in the sensor and shown this to not be a limiting factor.

HoQIs impact on the performance of the seismic isolation system has also been quantified, through the use of a accurate model of an Advanced LIGO isolation platform that I have developed. Using the model I have shown that using using HoQI, the expected isolation platform motion can be reduced by a factor of 70 at 0.1 Hz and a factor of 10 at 2 Hz. I have shown that the control filters used in this model can be improved by up to 70% by designing them using particle swarm optimisation.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Licence: All rights reserved
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Physics and Astronomy
Funders: Science and Technology Facilities Council
Subjects: Q Science > QC Physics


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