We present the design and implementation of a mechanical low-pass filter vibration isolation used to reduce the vibrational noise in a cryogen-free dilution refrigerator operated at 10 mK, intended for scanning probe techniques. We discuss the design guidelines necessary to meet the competing requirements of having a low mechanical stiffness in combination with a high thermal conductance. We demonstrate the effectiveness of our approach by measuring the vibrational noise levels of an ultrasoft mechanical resonator positioned above a SQUID. Starting from a cryostat base temperature of 8 mK, the vibration isolation can be cooled to 10.5 mK, with a cooling power of 113 μW at 100 mK. We use the low vibrations and low temperature to demonstrate an effective cantilever temperature of less than 20 mK. This results in a force sensitivity of less than 500 zN/Hz, and an integrated frequency noise as low as 0.4 mHz in a 1 Hz measurement bandwidth.
@article{arxiv.1810.06847,
title = {Vibration isolation with high thermal conductance for a cryogen-free dilution refrigerator},
author = {Martin de Wit and Gesa Welker and Kier Heeck and Frank M. Buters and Hedwig J. Eerkens and Gert Koning and Harmen van der Meer and Dirk Bouwmeester and Tjerk H. Oosterkamp},
journal= {arXiv preprint arXiv:1810.06847},
year = {2019}
}