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3 October 2016 Overhauser magnetometer sensor design for magnetic field observation
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The Overhauser magnetometer, with its unique set of advantages, such as low power consumption, high precision and fast recording ability has been widely used in geophysical mineral and oil exploration, archeology, environmental survey, ordnance and weapons detection (UXO) and other earth science applications. Compared with the traditional proton magnetometer, which suffers from high power consumption and low precision, the Overhauser magnetometer excite the free radical solution in a cavity with RF signal to enhance nuclear magnetic resonance (NMR). Thus, RF resonator plays a crucial role in reducing power consumption and improving the accuracy of Overhauser magnetometer. There are a wide variety of resonators, but only two of them are chosen for Overhauser magnetometer: birdcage coil and coaxial resonator. In order to get the best RF cavity for Overhauser magnetometer sensor, both resonators are investigated here. Firstly, parameters of two RF resonators are calculated theoretically and simulated with Ansoft HFSS. The results indicate that birdcage coil is characterized by linear polarization while coaxial resonator is characterized by circular polarization. Besides, all RF fields are limited inside of the coaxial resonator while distributed both inside and outside of the birdcage coil. Then, the two resonators are practically manufactured based on the theoretical design. And the S-parameter and Smith chart of these resonators are measured with Agilent 8712ES RF network analyzer. The measured results indicate that the coaxial resonator has a much higher Q value(875) than the birdcage coil(70). All these results reveal a better performance for coaxial resonator. Finally, field experimental shows 0.074nT sensitivity for Overhauser magnetometer with coaxial resonator.
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Zan Li, Shudong Chen, Shuang Zhang, Xin Guo, and Qiong Cao "Overhauser magnetometer sensor design for magnetic field observation", Proc. SPIE 9969, Radiation Detectors: Systems and Applications XVII, 99690Q (3 October 2016);

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