Quantum Magnetometers for Rapid Identification of Resonance Frequencies in Explosives, Pharmaceuticals, and Other Substances

晶体固体，如炸药和药物，具有固有的共振，为材料提供了独特的射频指纹。简单地用磁波以其共振频率激发样品，就会产生信号。 然而，微弱的信号强度和长达数月的对未经研究的材料中共振的搜索阻止了这种廉价而简单的技术，即核四极共振。 量子磁力计的灵敏度优于标准线圈探测器，有助于解决前一个问题，但在这个项目中，它将被开发用于提高搜索速度，可能比传统方法快五个数量级。 尽管很难发现新的共振线，但研究人员已经在对安全和社会至关重要的几个应用中使用四极共振进行物质检测;特别是在检查站检测爆炸物和识别假冒真实的药品。如果能够快速识别新材料的共振线，那么四极共振在检查点和标准应用中的应用将大大扩展。 除了国家安全的好处，该项目将提高科学，技术，工程和数学教育在乔治梅森锻造之间的紧密联系，通过振兴实验室课程的电气工程和物理部门。此外，通过创建以K-12教育经验为重点的本科生实习项目，将培养初出茅庐的科学教师，并为多样化和有竞争力的技术和工程劳动力播下种子。原子磁力计是与线圈根本不同的传感器。 使用光学排列的原子作为检测介质，并使用激光器对传感器进行光学读出，可以提供比线圈更好的检测灵敏度;磁力计中的噪声从根本上受到量子波动的限制。 此外，磁力计的工作频率可以很容易地改变，以匹配具有小静磁场的激励频率。 鉴于这些优点，与单一工作频率的脉冲激励相反，激励频率可以连续扫描，从而无需逐点搜索。 在脉冲激励下，材料必须在采集另一个信号之前恢复到平衡状态;数据采集之间通常需要长时间的等待。 然而，通过扫过更高的频率，然后回到原始频率，材料会自动恢复平衡。 以这种方式，避免了损害标准脉冲技术的有效性的长等待时间。 作为该项目的一部分，将实现以下目标：1）将设计和建造有效体积为2立方厘米的磁力计单元。 由此产生的磁力计将具有亚毫微微特斯拉的灵敏度。小体积对于用有限数量的材料进行共振搜索的实际实施是至关重要的。2）将磁力计连续调谐到变化的频率不会改变其灵敏度。3）当将100微特斯拉量级的共振激励施加到几厘米远的样品时，磁力计的灵敏度可以保持。将采用使用第二磁力计的线圈几何形状和共模抑制方案。4）如果实现上述三个目标，则谐振频率的搜索速度可以比传统技术提高多达五个数量级。

Crystalline solids, such as explosives and pharmaceuticals, have intrinsic resonances that provide a unique radio-frequency fingerprint for the material. Simply exciting the sample with a magnetic wave at its resonance frequency, yields a signal. However, weak signal strength and months-long searches for resonances in unstudied materials prevent ready adoption of this inexpensive and simple technique, known as nuclear quadrupole resonance. Quantum magnetometers, with sensitivities better than standard coil detectors, help with the former problem, but will, with this project, be developed to increase the search speed, potentially five orders of magnitude faster than the conventional method. Despite the difficulty of discovering new resonance lines, researchers have pursued the use of quadrupole resonance for substance detection in a few applications of critical importance for security and society; in particular, the detection of explosives and the identification of counterfeit from real medicine at checkpoints. The adoption of quadrupole resonance for checkpoint and standards applications would greatly expand if resonance lines could be quickly identified for new materials. In addition to national security benefits, the project will improve science, technology, engineering and mathematics education within George Mason by forging strong ties between the Electrical Engineering and Physics Departments through revitalized laboratory courses. Furthermore, by creating undergraduate internship projects focused on K-12 educational experiences, fledgling science teachers will be nurtured and seeds of a diverse and competitive technology and engineering workforce will be planted.Atomic magnetometers are fundamentally different sensors than coils. The use of optically aligned atoms as the detection medium and optical read-out of the sensor with a laser gives a better detection sensitivity than coils; noise in the magnetometer is fundamentally limited by quantum fluctuations. Moreover, the operating frequency of the magnetometer can easily be changed to match the frequency of the excitation with a small static magnetic field. In light of these advantages, the excitation frequency can be swept continuously, as opposed to pulsed excitation at a single operating frequency, obviating the need for a point by point search. With pulsed excitation the material must return to an equilibrium condition before another signal is acquired; often long wait times are required between data acquisitions. However by sweeping up through higher frequencies, then back down to the original frequency, the material is automatically returned to equilibrium. In this way, the long wait times that compromise the effectiveness of standard pulse techniques is avoided. As part of the project, the following goals will be met: 1) Magnetometer cells with an active volume of 2 cm3 will be designed and constructed. The resulting magnetometer will have sub-femtoTesla sensitivity. The small volume is critical for the practical implementation of the resonance search with a limited quantity of material.2) Continuously tuning the magnetometer to a changing frequency will not alter its sensitivity.3) The sensitivity of the magnetometer can be retained while resonant excitation on the order of a 100 micro Tesla is applied to a sample a couple centimeters away. Coil geometry and common mode rejection schemes using a second magnetometer will be employed.4) If the above three goals are achieved, the search speed for resonance frequencies can be improved by as much as five orders of magnitude over conventional techniques.