基于预极化磁共振技术的弱磁场宽量程精确测量方法

核磁共振磁强计是利用原子共振频率与磁场强度的严格线性相关性而制成的磁场精密测量仪器,但受信噪比限制,其测量范围一般≥20 mT。为了拓展其对弱磁场的测量能力,研究了一种基于预极化技术的流水式磁共振磁场测量方法。通过构建测量过程的数学物理方程,给出了测量曲线的优化方法;通过预极化处理,将磁共振信号强度提高了4.54倍;通过CPMG序列进行信号检测,提高了测量稳定性并降低了硬件需求;通过数据拟合提高了测量速度和精度。最终,在48mT的低均匀度(约2×10^-4)自制核磁共振设备中实现了对0.0788~1.373mT磁场的宽量程高精度测量,且测量精度<0.1μT。

Precise Wide-range Measurement Method of Weak Magnetic Field Based on Pre-polarized Magnetic Resonance Technique

Magnetic resonance magnetometer is a precision measuring instrument based on the strict linear correlation between the frequency of nuclear resonance and the strength of magnetic field.However,due to the limitation of bad SNR in weak field,its measurement range is generally not less than 20 mT.In order to expand its ability to measure weak magnetic field,a new method using flowing water based on the pre-polarization technology was studied.By constructing the mathematical physics equation of the measuring process,the optimization method of the measurement curve was given.By pre-polarization treatment,the intensity of the magnetic resonance signal increased by 4.54 times.By using the CPMG sequence in signal detection,the hardware demand reduced and the stability of the measurement could be enhanced.By data fitting,the measurement speed and precision were improved.Finally,the width range of 0.078 8~1.373 mT magnetic field was measured in a homemade 48 mT nuclear magnetic resonance device with low uniformity(about2×10^-4),and the measurement accuracy was less than 0.1μT.