Demonstration of a Quazi-Zero Stiffness Vibration Isolator for Cryogen-Free Scanned Probe Microscopy*

We demonstrate a fully passive vibration damping system based on quasi-zero stiffness (QZS) flexures that can provide isolation from the low-frequency noise introduced by a cryogen-free dilution refrigerator pump. The QZS flexures we design and test can effectively lower the resonance frequency of the isolator into the sub-Hz range. They also exhibit hysteresis in their force vs. distance curves, which adds damping to the isolation system without the need of magnets or piston. We will show how these flexures can be optimized to more strongly display these advantageous features for different conditions. The system we design is effective at sub-Kelvin temperatures and compact enough to fit inside a dilution refrigerator, which could make it useful for future cryogen-free low temperature scanning probe microscopy applications.