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

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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.