高灵敏度Overhauser磁力仪传感器关键问题研究

The Overhauser proton magnetometer (OPM) utilizes the dynamic nuclear polarization (DNP) effect to measure the magnetic field strength, which is one order of magnitude higher than that of conventional proton magnetometers, and can be used to identify more weak magnetic anomalies, and has been widely used in terrestrial, marine, airborne and satellite magnetism. At present, the 14N free radical working material used in the magnetometer sensor has the disadvantage of weak DNP effect, which makes it difficult to improve the sensitivity. In order to solve this problem, this project adopts the narrower 15N radical and paramagnetic metal ion doping of electron resonance spectrum to realize the enhancement of DNP effect. The effect of alcohol and ether on DNP enhancement is studied to achieve extreme cold conditions DNP enhancement. The effect of doping on the longitudinal relaxation time (T1) is studied to shorten the T1 and improve the response speed of the sensor. The effect of doping on the lateral relaxation time (T2) is studied to prolong T2 and improve the sensitivity of OPM. Optimize the sensor material, structure and electromagnetic compatibility design to improve the Q value, the stability of the sensor, and the anti-jamming ability. Through the above research, the sensor working material DNP enhancement strategy and the sensor design method are established at the basic research level, the OPM sensitivity 5pT, the low temperature working limit -40 ℃, and the 0.2s rapid measurement are realized.

Overhauser质子磁力仪（OPM）利用动态核极化（DNP）效应测量磁场强度，由于其灵敏度比传统质子磁力仪高一个数量级，可以识别更微弱的磁异常，已广泛用于陆地、海洋、航空和星载测磁。目前该磁力仪传感器所采用的14N自由基工作物质存在DNP效应弱的缺点，使其灵敏度难以提高。为解决这一难题，本项目采用电子共振谱线更窄的15N自由基和顺磁金属离子掺杂实现DNP效应增强；研究醇、醚类物质对DNP增强的影响，实现极寒条件下DNP效应增强；研究掺杂对纵向弛豫时间（T1）的影响，以缩短T1，提高传感器响应速度；研究掺杂对横向弛豫时间（T2）的影响，以延长T2，提高传感器灵敏度；优化传感器材料、结构和电磁兼容设计，提高传感器的Q值、稳定性和抗干扰能力。通过以上研究，在基础研究层面上确立传感器DNP增强策略和传感器设计方法，使OPM灵敏度达到5pT，低温工作极限达到-40℃，实现0.2s快速测量。

Overhauser质子磁力仪（OPM）利用动态核极化（DNP）效应测量磁场强度，由于其灵敏度比传统质子磁力仪高一个数量级，可以识别更微弱的磁异常，已广泛用于陆地、海洋、航空和星载测磁。采用14N自由基工作物质的磁力仪传感器存在DNP效应弱的缺点，使其灵敏度难以提高。为解决这一难题，本项目采用了电子共振谱线更窄的15NTEMPONE自由基和顺磁金属Na离子掺杂实现DNP效应增强，拉莫尔信号幅度增强1.5倍，横向弛豫时间提高3倍，信噪比接近100/1。通过研究醇、醚类物质对DNP增强的影响，最终选用DME为溶剂，实现极-40℃~+70℃宽温度范围DNP增强测磁。由于横向弛豫时间接近3s，信号幅度提高1.5倍，成功实现0.2s、0.5s、1.0s、2.0s、3.0s和3.0s+多测量周期可选测磁。通过优化传感器材料、结构和电磁兼容设计，解决了谐振腔材料易氧化问题，通过调控导电漆的电导率实现对涡流的抑制，提高传感器的Q值至1278，与理想的理论值1400非常接近，提高了RF激发效率、降低了RF功耗，且具有较强抗干扰能力。研制出JOM-4S和JOM-4SF两个型号Overhauser磁力仪，JOM-4S为间歇式慢读仪器，JOM-4SF为慢读和快读复合型仪器。技术指标分别为：野外自测0.0079nT@3s，0.022nT@1s，实验室自测0.0027nT@3s，第三方检测（宜昌中船重工710所国防科技工业一级计量站）0.01nT@3s，0.019nT@1s，梯度容限达到15000nT/m，测量范围20µT~120µT，温度范围-40℃~+70℃，功耗2W，测量速率0.2s、0.5s、1.0s、2.0s、3.0s、3.0s+可调。主要技术指标均达到和超过加拿大GSM-19型Overhauser磁力仪。Overhauser磁力仪的终极研究目标是通过关键技术的研究尽快实现产业化，尽快服务国家重大需求。因此，对磁力仪的功能进行了完善和提高，目前JOM-4SF增加了GPS/北斗定位和授时功能、两台/多台仪器的同步功能、外触发功能、仪器日变校正功能、上位机日变校正功能、上位机数据传输功能、上位机坐标变换功能等，Overhauser磁力仪的成熟度达到较高水平。