Thermometry Techniques
Vibrating Wire Resonators (VWRs)
In the ULT Group, most of our experimental measurements are made using Vibrating Wire Resonators (VWRs). These VWRs are tiny loops of superconducting wire, barely visible with the naked eye.
By placing the VWR in a low magnetic field and applying a small AC drive signal through it, the VWR can be made to oscillate perpendicular to the applied field, due to the Lorentz force.
The voltage generated as the VWR moves in the magnetic field is measured using a lock-in amplifier. If we monitor the voltage response and the frequency at which mechanical resonance occurs, we can calculate the damping that the VWR experiences.
When the temperature of the fluid that the VWR is immersed in changes, so will the damping on the VWR. As the wires are very thin it allows us to accurately measure tiny changes in temperature in our experiments.
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