Surface nuclear magnetic resonance (SNMR) technology is widely used in the detection of groundwater. However, the dead time arising from the coupling effect of the transmitting circuit on the receiving coil results in partial or complete loss of the SNMR signal. This situation is especially unfavorable for the detection of short relaxation time targets. To solve this problem, we analyzed the shortcomings of the traditional SNMR launch system, and we propose a new transmission method based on an untuned constant voltage-clamped technology to overcome the problems of high resonance voltage, an uncontrollable shutdown process, and long shutdown times. Untuned transmission topology without a matching capacitor, pulse width modulation, and a constant voltage-clamped technique were applied to guide the current rise and shutdown of the system in a controllable way using an integer-period transmission pulse. A simulation experiment comparing the traditional method of transmission and this new method was conducted. The results showed that not only can the new method control the transmission current shutdown process but it can also avoid the delay in response. When the transmitting current drops from 10 A to 0.12 µA, the traditional method requires 2.29 ms and the new method requires only 4 µs. The new transmission system that we have developed based on an untuned constant voltage-clamped technology can improve the level of the transmitting current effectively and shorten the shutdown time.

中文翻译：

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使用短关断时间传输电流进行表面核磁共振的改进技术

地表核磁共振（SNMR）技术广泛应用于地下水的检测。然而，由于发射电路对接收线圈的耦合效应产生的死区时间导致SNMR信号部分或全部丢失。这种情况尤其不利于短弛豫时间目标的检测。针对这一问题，我们分析了传统SNMR发射系统的不足，提出了一种基于非调谐恒压钳位技术的新型发射方式，克服了谐振电压高、关断过程不可控、关断时间长等问题。 . 无匹配电容器的未调谐传输拓扑、脉宽调制、应用恒压钳位技术以可控方式引导系统的电流上升和关闭，使用整数周期传输脉冲。对传统的传输方法和这种新方法进行了仿真实验。结果表明，新方法不仅可以控制输电电流关断过程，而且可以避免响应延迟。当传输电流从 10 A 下降到 0.12 µA 时，传统方法需要 2.29 ms，而新方法只需要 4 µs。我们基于非调谐恒压钳位技术开发的新型传输系统可以有效提高传输电流的水平，缩短关断时间。对传统的传输方法和这种新方法进行了仿真实验。结果表明，新方法不仅可以控制输电电流关断过程，而且可以避免响应延迟。当传输电流从 10 A 下降到 0.12 µA 时，传统方法需要 2.29 ms，而新方法只需要 4 µs。我们基于非调谐恒压钳位技术开发的新型传输系统可以有效提高传输电流的水平，缩短关断时间。对传统的传输方法和这种新方法进行了仿真实验。结果表明，新方法不仅可以控制输电电流关断过程，而且可以避免响应延迟。当传输电流从 10 A 下降到 0.12 µA 时，传统方法需要 2.29 ms，而新方法只需要 4 µs。我们基于非调谐恒压钳位技术开发的新型传输系统可以有效提高传输电流水平并缩短关断时间。12 µA，传统方法需要 2.29 ms，而新方法只需要 4 µs。我们基于非调谐恒压钳位技术开发的新型传输系统可以有效提高传输电流的水平，缩短关断时间。12 µA，传统方法需要 2.29 ms，而新方法只需要 4 µs。我们基于非调谐恒压钳位技术开发的新型传输系统可以有效提高传输电流的水平，缩短关断时间。