This Phase I Small Business Technology Transfer (STTR) project will demonstrate that a full-spectrum Raman analyzer prototype with no moving parts that incorporates a small, novel Raman optical-fiber based enhancement cell can rapidly measure Ethylene Oxide (EtO) and other gases down to low ppm levels. Raman's high degree of specificity minimizes signal cross-talk in complex multicomponent systems. The spectra have narrow peaks which can be observed easily even in the presence of moisture. In order to make gas-phase Raman analysis affordable and practical we will use an off-the- shelf laser diode array as a light source. A proprietary external-cavity configuration will narrow the linewidth to around 10 cm-1. A simple, fiber-optic loop will enhance the circulating laser energy by approximately 10 X to obtain sufficiently high laser energy for gas-phase detection at low concentrations. The Raman signal will be collected with a rugged, optically fast (f/1.4) volume- holographic spectrograph, and the full spectrum will be detected using a sensitive TE-cooled CCD array detector. This approach offers a simple, reliable instrument with no moving parts, for reduced maintenance and good stability. EtO is a colorless gas commonly used for sterilization of medical products that are temperature sensitive, which has been demonstrated to be a respiratory, skin, and eye irritant even at low concentrations (50 ppm). In addition, long-term exposure to EtO presents mutagenic, reproductive, and carcinogenic complications to humans. Below 700 ppm the odor of EtO cannot be detected. A gas sensor is needed to rapidly monitor EtO. The proposed work will demonstrate the ease of use and breadth of application of Raman instrumentation compared to conventional IR, mass spectroscopy, or GC methodologies in a large U.S. market for industrial process analyzers.
