SBIR Phase I: Fiber-Loop Cavity Ring-Down Spectroscopy for Contamination Monitoring in Cryogenic Liquids

这项小型企业创新研究计划（SBIR）第一阶段项目将开发一种“光纤环路腔衰荡光谱仪”，以满足对原位测量低温液体中污染物的迫切需求。由于缺乏测量液相杂质的方法，低温液体制造商及其用户必须依赖于容器顶空的气体样品或提取和蒸发的样品。这种方法成本高、耗时长，而且容易出错。开发用于低温应用的浓度传感器的两个主要障碍是实现足够低的检测限和在极低的温度下工作。对于第一阶段的项目，腔衰荡光谱，提供非常低的检测限制，将与光纤相结合，这已被证明在低温下工作良好。光纤环路，由一束光纤组成的环形腔，必须包含一个传感部分，以允许引导光与样品相互作用。由于传感部分最终决定传感器的检测极限，因此将多个光纤锥或没有包层的光纤部分纳入环路并优化灵敏度。该装置将在低温液体中进行快速、准确和敏感的测量。该项目的广泛影响/商业潜力服务于低温液体的各种应用，如高纯度气体制造；冷却高科技设备，包括磁共振成像（MRI）；氢燃料电池；冷冻食品;血库和生物技术应用，如冷冻疫苗和化学反应的执行。低温处理系统内的水分积聚会导致结冰和堵塞，造成安全风险。用于高纯度气体生产的低温液体中杂质水平的增加减少了净化器的使用寿命，并导致使用时的污染。氢燃料电池提供比传统能源更清洁、更高效的电力，但需要相对无污染的材料来保证其性能和使用寿命。用于冷冻食品以及生物和医学样品的低温液体的纯度具有公共卫生影响。在这里，对苯、一氧化碳和生物物种（病毒、细菌）等潜在有害污染物的现场测量至关重要。监测液相中污染物的有效和负担得起的手段将提高安全性，减少浪费并促进更好的过程控制。

This Small Business Innovation Research Program (SBIR) Phase I project will develop a "Fiber-loop Cavity Ring-down spectrometer" to address the critical need for an in situ means to measure contaminants in cryogenic liquids. Lacking a way to measure impurities in the liquid phase, cryogenic liquids makers and their users must rely upon gaseous samples from the headspace of the container or extracted and evaporated samples. Such methods are costly, time-consuming and tend to be error-prone. The two major hurdles in developing a concentration sensor for cryogenic applications are achieving sufficiently low detection limits and operating at extremely low temperatures. For the Phase I project, Cavity Ring-down Spectroscopy, offering very low detection limits, will be combined with optical fibers, which have been proven to work well at cryogenic temperatures. The Fiber-loop, a ring-cavity comprising a strand of optical fiber, must contain a sensing section to permit the guided light to interact with the sample. Since the sensing section ultimately determines the detection limits of the sensor, multiple fiber tapers or a fiber section without cladding will be incorporated into the loop and optimized for sensitivity. The resultant device will perform fast, accurate and sensitive measurements in cryogenic liquids. The broader impact/commercial potential of this project serves diverse applications of cryogenic liquids, such as high-purity gas manufacture; cooling high-tech equipment, including magnetic resonance imaging (MRI); hydrogen fuel cells; frozen food; blood banks and biotechnological applications, such as freezing vaccines and execution of chemical reactions. Moisture build-up within cryogenic processing systems promotes ice and blockages, posing a safety risk. Increased levels of impurities in cryogenic liquids for high-purity gas production reduce purifier lifetimes and lead to contamination at the point of use. Hydrogen fuel cells offer cleaner and more efficient power than traditional sources, but require relatively contamination-free materials to guarantee their performance and lifetime. The purity of cryogenic liquids used to freeze food, as well as biological and medical samples, has public health implications. Here, in situ measurements of potentially harmful contaminants, such as benzene, carbon monoxide and biological species (viruses, bacteria), are critical. An effective and affordable means of monitoring contaminants in the liquid phase will improve safety, reduce waste and promote better process control.