Measurement of the thermal accommodation coefficient of helium on a crystalline silicon surface at low-temperatures

Alexander Franke; Nils Sültmann; Christoph Reinhardt; Sandy Croatto; Jörn Schaffran; Hossein Masalehdan; Axel Lindner; Roman Schnabel

arXiv · 2402.11977

Measurement of the thermal accommodation coefficient of helium on a crystalline silicon surface at low-temperatures

Alexander Franke·Nils Sültmann·Christoph Reinhardt·Sandy Croatto·Jörn Schaffran·Hossein Masalehdan·Axel Lindner·Roman Schnabel

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Abstract

Next-generation gravitational wave observatories are expected to use cryogenically cooled, pendulum-suspended 200 kg test mass mirrors from a crystalline material such as crystalline silicon. During operation of the observatories, these mirrors undergo heating due to the absorption of laser radiation of up to a watt. Low noise cooling techniques need to be developed. Low-pressure helium exchange gas at 5 K might contribute to the challenging task. Here, we report the measurement of the helium accommodation coefficient $\alpha(11\,\mathrm{K} 0.7$ for temperatures < 20 K, which increases the cooling power compared to recently used assumptions. The idea of free molecular flow helium gas cooling is thus supported and might find application in some observatory concepts.

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Alexander Franke, Nils Sültmann, Christoph Reinhardt, Sandy Croatto, Jörn Schaffran, Hossein Masalehdan, Axel Lindner, Roman Schnabel. 2024-02-19. Measurement of the thermal accommodation coefficient of helium on a crystalline silicon surface at low-temperatures. https://arxiv.org/abs/2402.11977

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