ET R&D

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Gravitational waves are the last prediction of general relativity still awaiting direct experimental detection. The efforts in constructing and optimising large interferometers in different locations all over the world in the last two decades have resulted in instruments of extraordinary sensitivity. While the British/German gravitational wave detector GEO 600 is currently taking data, the American LIGO detectors and the Franco/Italian Virgo detector are being upgraded to further increase their sensitivity. Once these upgrades have reached their design sensitivity the theoretical estimates predict the detection of gravitational waves within a few months to a year. Although frequent detections will be possible, the detection of high signal to-noise ratio events, allowing precision gravitational wave astronomy, will be very rare.The ET-R&D project is aimed at essential R&D tasks in preparation for a technical design of the Einstein Telescope, a 3rd generation, underground gravitational wave detector. It is widely expected that this detector will allow routine gravitational wave astronomy to take place. While the basic design mostly relies on techniques well developed and tested for the advanced detectors, several aspects still require R&D with long lead times. We propose to target the most important of these topics in this ET-R&D project via 5 working groups (WGs).WG1 will explore how well astrophysical source models and GR itself can be tested with ET, and how much information on the dynamics of the universe can be extracted from the data. WG2 will collect long term seismic data for various candidate sites and develop methods for measuring the seismic motion which directly couples to the test mass motion, with the goal of developing subtraction techniques. WG3 will investigate properties of cryogenic optics essential for lowering detector thermal noise and providing good low frequency performance. The control of various interferometer degrees of freedom and noise correlations in the data of the three different ET detectors will be studied in WG4. WG5 will focus on overall project management. Glasgow University will play a key role in three of the working groups. In WG1, we will develop methods of parameter estimation for transient signals detected by ET, through application of our existing expertise in gravitational wave data analysis. In WG3 we will develop apparatus for measuring the birefringence of coated silicon samples and apply our expertise in finite element modelling to assist in the interpretation of cryogenic birefringence measurements carried out in collaboration with Hannover and Jena. In WG4 we will carry out studies and simulations of sensing and control issues for ET and carry out detailed modelling of the quantum noise and optical configuration. Collaboration with our UK and European partners and combination of the facilities and expertise available will be essential for the success of this proposal.