Construction of a precise measuring probe based on tunnel diode oscillator

Abstract

Metrology utilizing resonance techniques is a cornerstone for precise measurement of small signals. Resonances in mechanical oscillation, electric circuit, electromagnetic circuit, and optical cavity have been proven as powerful tools across a wide spectral range. In this study, we present the construction and characterization of a tunnel diode oscillator (TDO) circuit optimized for operating at cryogenic temperatures down to $1.5K$. By taking advantage of the negative differential resistance (NDR) of a tunneling diode (TD), the TDO circuit is able to sustain a continuous oscillation. A quality factor of $Q\approx 3.5\times {10}^5$ is achieved by careful optimization of the circuit's operating point, thus realizing sensitive detection of variations in inductance and capacitance. The TDO circuit is integrated to a cryostat insert and converted as a measuring probe for magnetic properties. We tested the probe by characterizing the superconducting transition of niobium. The evolution of magnetic penetration depth (λ) was measured with an uncertainty of around 0.2% across the transition in various magnetic field. Our results demonstrate the significant potential of TDO technique for cryogenic studies in physical sciences.