Rostock 2019 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 57: Poster: Quantum Optics and Photonics III

Q 57.25: Poster

Thursday, March 14, 2019, 16:15–18:15, S Fobau Physik

Gas-mediated mirror cooling for cryogenic gravitational-wave detectors — •Mikhail Korobko and Roman Schnabel — Institut für Laserphysik und Zentrum für Optische Quantentechnologien, Universität Hamburg, Luruper Chaussee 146, 22761 Hamburg

Thermal fluctuations in mirrors and suspensions limit the sensitivity of gravitational-wave observatories (Advanced LIGO, Advanced Virgo and KAGRA). The most direct way to reduce these fluctuations is to cryogenically cool the mirrors. Cryogenic technology is currently used in KAGRA, and is planned for future detectors, such as the Einstein Telesope. One of the main challenges of a cryogenic detector is extracting the heat out the mirrors without introducing additional noises. It can be done though the mirror’s suspensions, which need to be thick enough to ensure good thermal conductivity, but that reduces their mechanical quality and leads to additional thermal noises. The other approach of attaching soft links from the cold plate directly to the mirror substrate, lowers the mechanical quality of the substrate itself.

We propose an alternative: cooling the suspended mirrors by local buffer gas (e.g. helium). By design this gas is trapped between the side cylindrical surface of the mirror and the cold shield, transferring the heat from the mirror to the cold shield. The advantage of such approach is that the mirror suspensions are not used for heat extraction and can be optimized for best mechanical properties. The mirror in this approach is cooled uniformly, preventing the heat-induced deformations. We study the approach theoretically, analyse the optimal operational regime and the noise performance.