Novel Miniature Spectrometer For Remote Chemical Detection
New chemical sensing technologies are critically important for addressing many of EM's priority needs as discussed in detail at http://emsp.em.doe.gov/needs. Many technology needs were addressed by this research. For example, improved detection strategies are needed for non-aqueous phase liquids (NAPL's), such as PCE (Cl2C=CCl2) and TCE (HClC=CCl2), which persist in the environment due their highly stable structures. By developing a miniature, ultra-sensitive, selective, and field-deployable detector for NAPL's, the approximate source location could be determined with minimal investigative expense. Contaminant plumes could also be characterized in detail. The miniature spectrometer developed under Project No.60231 could also permit accurate rate measurements in less time, either in the field or the laboratory, which are critically important in the development, testing, and ultimate utilization of models for describing contaminant transport. The technology could also be used for long-term groundwater monitoring or long-term stewardship in general. Many science needs are also addressed by the Project 60231, since the effort significantly advances the measurement science of chemical detection. Developed under Project No.60231, evanescent wave cavity ring-down spectroscopy (EW-CRDS) is a novel form of CRDS, which is an the emerging optical absorption technique. Several review articles on CRDS, which has been generally applied only to gas-phase diagnostics, have been published1-3. EW-CRDS4-10 forms the basis for a new class of chemical sensors that extends CRDS to other states of matter and leads to a miniaturized version of the concept. EW-CRDS uses miniature solid-state optical resonators that incorporate one or more total internal reflection (TIR) surfaces, which create evanescent waves. The evanescent waves emanate from the TIR surfaces, sampling the surrounding medium. The utility of evanescent waves in chemical analysis forms the basis for the field of attenuated total reflectance (ATR)11 spectroscopy. Many diagnostic problems can be solved by ATR methods that are intractable by ordinary methods, but ATR typically lacks sensitivity for ultra-trace chemical detection. In EWCRDS, the ring-down time of a resonator sensitively responds to chemical species present in the evanescent wave thereby combining the advantages of ATR with the sensitivity of CRDS. Furthermore, EW-CRDS forms the basis for a rugged miniature chemical sensor for which the laser source and photodetector can be located remotely by using optical fiber. Work on EW-CRDS began at NIST with the NRC postdoctoral associateship of the current Principal Investigator during fiscal 1996-1997. Since completion of the NRC associateship, work on EW-CRDS has been majority funded through Project 60231, with some additional funding from the Advanced Technology Program (35K/year in 2000).
- Research Organization:
- National Institute of Technology, Gaithersburg, MD (US)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM) (US)
- DOE Contract Number:
- A107-97ER62518
- OSTI ID:
- 829899
- Report Number(s):
- EMSP-60231; R&D Project: EMSP 60231; TRN: US0404806
- Resource Relation:
- Other Information: PBD: 14 Sep 2000
- Country of Publication:
- United States
- Language:
- English
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