A Cryogenic Torsion Balance Using a Liquid-Cryogen Free, Ultra-Low Vibration Cryostat

TL;DR

This paper presents a cryostat that operates without liquid cryogens, providing ultra-low vibration conditions for torsion balance experiments at cryogenic temperatures, enabling more sensitive measurements.

Contribution

The authors introduce a liquid-cryogen free cryostat with passive vibration isolation that achieves low torque noise levels and supports continuous cryogenic torsion balance operation.

Findings

Torque noise below room temperature thermal noise by a factor of four

Achieved ultra-low vibration levels suitable for sensitive experiments

Identified limitations due to cryogenic surface contamination

Abstract

We describe a liquid-cryogen free cryostat with ultra-low vibration levels which allows for continuous operation of a torsion balance at cryogenic temperatures. The apparatus uses a commercially available two-stage pulse-tube cooler and passive vibration isolation. The torsion balance exhibits torque noise levels lower than room temperature thermal noise by a factor of about four in the frequency range of 3-10mHz, limited by residual seismic motion and by radiative heating of the pendulum body. In addition to lowering thermal noise below room-temperature limits, the low-temperature environment enables novel torsion balance experiments. Currently, the maximum duration of a continuous measurement run is limited by accumulation of cryogenic surface contamination on the optical elements inside the cryostat.