Jena 2013 – wissenschaftliches Programm

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GR: Fachverband Gravitation und Relativitätstheorie

GR 4: Gravitationswellen II

GR 4.3: Vortrag

Dienstag, 26. Februar 2013, 14:30–14:45, HS 6

Mechanical loss of sapphire at low temperatures — •Gerd Hofmann¹, Julius Komma¹, Christian Schwarz¹, Daniel Heinert¹, Paul Seidel¹, Andreas Tünnermann², and Ronny Nawrodt¹ — ¹FSU Jena, Institut für Festkörperphysik, Helmholtzweg 5, D-07743 Jena, Germany — ²FSU Jena, Institut für Angewandte Physik, Albert-Einstein-Strasse 15, D-07745 Jena, Germany

One crucial limit in the sensitivity of current gravitational wave observatories (GWOs) is given by the thermal noise from the test masses which is directly linked to their temperature and mechanical loss. Current detectors are operated at room temperature with fused silica. The reduction of thermal noise is possible by decreasing the temperature and the mechanical loss. So the next generation of GWOs like the Japanese KAGRA will be operated at cryogenic temperatures. However, fused silica shows a high mechanical loss at cryogenics. Thus new materials especially crystaline ones are required. In this sense sapphire is a promising candidate with low losses at low temperatures.

We present measurements from 5 to 300 K on bulk sapphire as well as sapphire fibers. Data analysis reveals that bulk sapphire is limited in its mechanical loss at lowest temperatures due to Akhiezer damping i.e. the interaction of phonons. In contrast, we found that sapphire fibers mainly follow the theoretical predictions of thermoelastic damping. We further discuss the influence of surface treatment and the supporting structure in detail.

This work is supported by the DFG under contract SFB TR7.