Overhauser Geomagnetic Sensor Based on the Dynamic Nuclear Polarization Effect for Magnetic Prospecting.
Based on the dynamic nuclear polarization (DNP) effect, an alternative design of an Overhauser geomagnetic sensor is presented that enhances the proton polarization and increases the amplitude of the free induction decay (FID) signal. The short-pulse method is adopted to rotate the enhanced proton magnetization into the plane of precession to create an FID signal. To reduce the negative effect of the powerful electromagnetic interference, the design of the anti-interference of the pick-up coil is studied. Furthermore, the radio frequency polarization method based on the capacitive-loaded coaxial cavity is proposed to improve the quality factor of the resonant circuit. In addition, a special test instrument is designed that enables the simultaneous testing of the classical proton precession and the Overhauser sensor. Overall, comparison experiments with and without the free radical of the Overhauser sensors show that the DNP effect does effectively improve the amplitude and quality of the FID signal, and the magnetic sensitivity, resolution and range reach to 10 pT/Hz 1 / 2 @1 Hz, 0.0023 nT and 20-100 μ T, respectively.
School of Automation, China University of Geosciences, Wuhan 430074, China. gejian@cug.edu.cn.|Science and Technology on Near-Surface Detection Laboratory, Wuxi 214035, China. gejian@cug.edu.cn.|Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074, China. gejian@cug.edu.cn.
Jian
J
Ge
School of Automation, China University of Geosciences, Wuhan 430074, China. cekong@cug.edu.cn.|Science and Technology on Near-Surface Detection Laboratory, Wuxi 214035, China. cekong@cug.edu.cn.
Haobin
H
Dong
Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074, China. liuhuancug@gmail.com.
Huan
H
Liu
Science and Technology on Near-Surface Detection Laboratory, Wuxi 214035, China. zhiwenyuan63@gmail.com.
Zhiwen
Z
Yuan
School of Mechanical Engineering and Electronic Information, China University of Geosciences, Wuhan 430074, China. donghe@2013.cug.edu.cn.
He
H
Dong
Science and Technology on Near-Surface Detection Laboratory, Wuxi 214035, China. edmundzhao74@gmail.com.
Zhizhuo
Z
Zhao
Science and Technology on Near-Surface Detection Laboratory, Wuxi 214035, China. liucheryl79@gmail.com.
Yonghua
Y
Liu
Science and Technology on Near-Surface Detection Laboratory, Wuxi 214035, China. zhujun0506@gmail.com.
Jun
J
Zhu
Science and Technology on Near-Surface Detection Laboratory, Wuxi 214035, China. 1987hyzhang@gmail.com.
Haiyang
H
Zhang
Overhauser geomagnetic sensor; anti-interference; dynamic nuclear polarization effect; free radical; resonant cavity