Rushton Lucas Martin, Ellis Laura Mae, Zipfel Jake David, Bevington Patrick, Chalupczak Witold
National Physical Laboratory, Hampton Road, Teddington TW11 0LW, UK.
Sensors (Basel). 2024 Oct 16;24(20):6657. doi: 10.3390/s24206657.
Measurements monitoring the inductive coupling between oscillating radio-frequency magnetic fields and objects of interest create versatile platforms for non-destructive testing. The benefits of ultra-low-frequency measurements, i.e., below 3 kHz, are sometimes outweighed by the fundamental and technical difficulties related to operating pick-up coils or other field sensors in this frequency range. Inductive measurements with the detection based on a two-photon interaction in rf atomic magnetometers address some of these issues as the sensor gains an uplift in its operational frequency. The developments reported here integrate the fundamental and applied aspects of the two-photon process in magnetic induction measurements. In this paper, all the spectral components of the two-photon process are identified, which result from the non-linear interactions between the rf fields and atoms. For the first time, a method for the retrieval of the two-photon phase information, which is critical for inductive measurements, is also demonstrated. Furthermore, a self-compensation configuration is introduced, whereby high-contrast measurements of defects can be obtained due to its insensitivity to the primary field, including using simplified instrumentation for this configuration by producing two rf fields with a single rf coil.
监测振荡射频磁场与感兴趣物体之间感应耦合的测量方法为无损检测创造了多功能平台。超低频测量（即低于3kHz）的优势有时会被在该频率范围内操作拾波线圈或其他场传感器所涉及的基本和技术难题所抵消。基于射频原子磁力计中双光子相互作用进行检测的感应测量解决了其中一些问题，因为传感器的工作频率得到了提升。本文报道的进展整合了磁感应测量中双光子过程的基础和应用方面。在本文中，识别了双光子过程的所有光谱成分，这些成分源于射频场与原子之间的非线性相互作用。首次展示了一种用于获取双光子相位信息的方法，该信息对于感应测量至关重要。此外，还引入了一种自补偿配置，由于其对主场不敏感，因此可以获得缺陷的高对比度测量结果，包括通过使用单个射频线圈产生两个射频场来为此配置使用简化的仪器。
