Nuclear magnetic resonance (NMR) is widely used in medicine, chemistry and industry. One application area is magnetic resonance imaging (MRI). Recently it has become possible to perform NMR and MRI in the ultra-low field (ULF) regime requiring measurement field strengths of the order of only 1 Gauss. This technique exploits the advantages offered by superconducting quantum interference devices or SQUIDs. Our group has built SQUID based MRI systems for brain imaging and for liquid explosives detection at airport security checkpoints. The requirement for liquid helium cooling limits potential applications of ULF MRI for liquid identification and security purposes. Our experimental comparative investigation shows that room temperature inductive magnetometers may provide enough sensitivity in the 3-10 kHz range and can be used for fast liquid explosives detection based on ULF NMR technique. We describe experimental and computer-simulation results comparing multichannel SQUID based and induction coils based instruments that are capable of performing ULF MRI for liquid identification.

中文翻译：

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SQUID 与用于超低场核磁共振的感应线圈：实验和模拟比较

核磁共振 (NMR) 广泛应用于医学、化学和工业。一个应用领域是磁共振成像（MRI）。最近，在超低场 (ULF) 范围内执行 NMR 和 MRI 已成为可能，只需要 1 高斯量级的测量场强。该技术利用了超导量子干涉设备或 SQUID 提供的优势。我们的团队已经建立了基于 SQUID 的 MRI 系统，用于大脑成像和机场安全检查站的液体爆炸物检测。液氦冷却的要求限制了 ULF MRI 在液体识别和安全方面的潜在应用。我们的实验比较研究表明，室温感应磁力计可以在 3-10 kHz 范围内提供足够的灵敏度，可用于基于 ULF NMR 技术的快速液体爆炸物检测。我们描述了实验和计算机模拟结果，比较了基于多通道 SQUID 和基于感应线圈的仪器，这些仪器能够执行 ULF MRI 以进行液体识别。