Commercial Accelerometers for Vibration Sensing at mK Temperatures in Dry Dilution Refrigerators

TL;DR

The paper tackles the challenge of measuring and monitoring vibrations due to pulse-tube cryocoolers in dry dilution refrigerators at millikelvin temperatures. It demonstrates that off-the-shelf accelerometers can operate at $8~\mathrm{mK}$, enabling continuous, in situ vibration sensing near the experimental volume, and it presents a cryogenic setup with careful thermal and electromagnetic management to minimize heat load. The authors show PT harmonics are detectable across a tri-axial accelerometer array, assess the thermal and radioactivity implications, and propose a cross-spectral approach for denoising using witness sensors. These findings offer a practical path to real-time vibrational monitoring and mitigation in cryogenic experiments, with potential impact on calorimetric sensitivity and quantum sensing applications.

Abstract

This article presents an evaluation of off-the-shelf commercial accelerometers at the mixing chamber stage of a cryogen-free dilution refrigerator at temperatures down to 8 mK. In addition, we present results of radioassay of accelerometer samples using a high purity germanium detector counting setup. Cryogen-free dilution refrigerators using pulse-tube cryocoolers (PTs)-due to recent advances in their cooling capacity, long-term stability, and operational costs-have become ubiquitous tools in a wide range of fields ranging from experimental particle physics to quantum information sciences. However, vibrations induced by PTs can negatively impact the experimental payload in these applications. This work demonstrates that commercially available accelerometers can not only measure vibrations at millikelvin cryogenic temperatures but also pave the way for continuous, in situ, real-time vibration monitoring of dry dilution refrigerators.

Figures (10)

• Figure 1: (Top): Schematic of the cryostat as seen from the top showing the placement of the mounting blocks. Also shown are their placements relative to the PT head. The strongest impulse from PTs is approximately along the Y-axis on the schematic. Only the 300K and the MC plate are shown for the sake of clarity. (Bottom): Lateral view of the measurement setup.
• Figure 2: Photograph of the mounting block with all three 2271A accelerometers mounted in a triaxial setup, as used for all the measurements. Also visible on top of the mounting block is the RuOx thermometer.
• Figure 3: (Top): Raw voltage time series data of a 393B31 accelerometer and a 2271A accelerometer, clearly showing a drift in the baseline of the 2271A accelerometer. (Bottom): The same data smoothed by applying a 0.5 s rolling average subtraction. The baseline voltage drift was corrected for the 2271A accelerometers, while no noticeable variations were observed in the 393B31 accelerometers.
• Figure 4: (Top): Time series of 2271A accelerometer voltage on the MC plate with no Kapton tape electrical insulation. (Bottom): Time series of 2271A accelerometer voltage on the MC plate with Kapton tape on brass screws and the interface between mounting block and accelerometer. Notice the difference in voltage scales between the two figures.
• Figure 5: ANPS of 2271A accelerometers, after MC plate stabilized at 8 mK, when the PT was on (solid lines) and turned off (dotted lines). Also shown are the 1.4 Hz base frequency of the PT and its next nine harmonics clearly illustrating the sensitivity of the accelerometers to vibrations.