Accurate temperature measurement of miniaturization NMR sensor in vacuum environment

The nuclear magnetic resonance (NMR) sensor is one of the core sensors in the inertial-grade navigation system, which has the advantages of higher precision and smaller volume. The vapor cell is the sensitive unit of NMR sensor, which is easily affected by temperature. In the process of miniaturization, NMR sensor needs to be reduced in size, which leads to poor thermal insulation performance. Thus, the heat transfer increases between cell and atmosphere environment, and the temperature uniformity of cell gets worse. The average temperature of cell is far from the operating temperature we require. In order to accurately measure the temperature of cell, a vacuum chamber is designed for NMR sensor. The vacuum chamber can provide a vacuum environment with 2.2 x 10-2Pa to isolate NMR sensor from the influence of atmosphere environment temperature. A fitting curve model is established to analyze the actual temperature in atmosphere by measuring the spin polarizability of alkali metal atoms. With this model, the temperature measurement error decreased by 2.45%, and temperature control will also be more accurate. Furthermore, the temperature uniformity simulated by ANSYS has improved by 83.33% in vacuum. It's important to provide a vacuum environment for the cell in miniaturization NMR sensor. If not, the fitting curve model also guarantees the accurate of temperature measurement and control.