DETECTION AND MEASUREMENT OF TRACE GASES BY CORRELATION INTERFEROMETRY: A REPORT

A report, now available, discusses the feasibility of detecting gases in a closed environment by correlation interferometry. The methods discussed are applicable to systems such as those used for detecting toxic, explosive, or polluting gases. Various techniques are available for evaluating gas concentrations, including mass spectroscopy, gas chromatography, and absorption spectroscopy techniques, such as dispersive correlation spectroscopy and nondispersive gas analyzers. The basic requirements which must be satisfied by a technique if it is to be considered for real-time monitoring are: (a) the capability of completing a gas analysis with only a short (less than 1 minute) delay; (b) the possibility of analyzing many selectable gases during a cycle, with good discrimination between gases (the rejection of interfering gases in the measurement of the target gas); and (c) the possibility of being developed into compact field instrumentation. Correlation interferometry is an analytical technique with the capability of satisfying all of these requirements. The report includes a detailed preliminary investigation of the theoretical maximum sensitivities to certain gases.