A compact and transportable infrared multicomponent acquisition (IRMA) system based on infrared absorption spectroscopy has been developed for plasma diagnostics and control. The IRMA system contains four independent tunable diode lasers which can be temporally multiplexed and directed into plasma reactors or into a multipass cell for exhaust gas detection. Rapid scan software with real-time line shape analysis provides simultaneous measurements of the absolute concentrations of several molecular species.
Abstract. A novel tunable diode laser absorption spectrometer (TDLAS) called TRISIAR (tracer in situ TDLAS for atmospheric research) has been developed for airborne tracegas measurements in the upper troposphere and lower stratosphere. Up to three different species can be measured simultaneously with high temporal resolution « 1 s) using up to three individual lead-salt diode lasers. The lasers are operated in a time-multiplexed mode using a novel modulation scheme that combines laser operation in a pulsed-current mode with a combination of rapid scanning and two-tone frequency modulation. The latter improves the signal-to-noise ratio of phasc-sensitive detection when compared to standard lockin techniques because of the reduction of instrument noise at higher detection frequencies. TRISTAR has been used in twochannel mode to measure CO and N 2 0 during two airborne polar stratospheric campaigns in January and March 1997. These species were detected using integration periods of 1 s with a precision of ±2%(3a) and a calibration accuracy of ±2,8% during a total of 11 measurement flights up to a maximum altitude of 12,5 km. More recently all three channels have been operated simultaneously for CO, CH 4 , and N 2 0 with comparable results. PACS: 39.90.+w; 93.85.+q; 94.10.Fa In recent years the technique oftunable diode laser absorption spectroscopy (TDLAS) has tound widespread application in the field of atmospheric research [I]. The technique is based on recording of individual rovibrational absorption lines of the target molecules in the mid-infrared spectral region and exploits the high spectral brightness and narrow tunable emission bandwidth of lead-salt diode lasers. By pumping the atmospheric sample rapidly through a low-pressure cell (approximately 50 mbar), the width of the pressure-broadened absorption line is reduced and overlap with other absorptions in air is minimized, resulting in excellent specificity. In addition, the sensitivity is enhanced by passing the laser beam through a multi-pass reflection cell, yielding sub-ppbv detection limits for many small molecules of atmospheric relevance, for example, HCHO. H 2 0 2 , N0 2 , HN0 3 , NH3, OCS, HCL C2H2, CO, CH4, and N20. TDLAS systems have been successfully applied for trace-gas detection throughout the troposphere and lower stratosphere on ground-based [2,3], shipboard [4], and airborne platlorms [2,[5][6][7][8]. Specialized instruments have been adapted for measurement of trace-gas fluxes using micrometeorological techniques [9,10] and for the measurement of the stable isotopomers in methane [11].Here we report on a newly developed computer-controlled, multi-laser tracer in situ TDLAS tor atmospheric research (TRISTAR) which is optimized tor high-precision (% range) air-borne trace-gas measurements with high temporal resolution (l Hz) in the tropopause region. In Sect. 1 the opticalmechanical setup ofthe instrument is described, and the electronic components (high-frequency modulation and detection scheme, instrument control. data acquisition) a...
The MASERATI (middle-atmosphere spectrometric experiment on rockets for analysis of trace-gas influences) instrument is, to our knowledge, the first rocket-borne tunable diode laser absorption spectrometer that was developed for in situ measurements of trace gases in the middle atmosphere. Infrared absorption spectroscopy with lead salt diode lasers is applied to measure water vapor and carbon dioxide in the altitude range from 50 to 90 km and 120 km, respectively. The laser beams are directed into an open multiple-pass absorption setup (total path length 31.7 m) that is mounted on top of a sounding rocket and that is directly exposed to ambient air. The two species are sampled alternately with a sampling time of 7.37 ms, each corresponding to an altitude resolution of approximately 15 m. Frequency-modulation and lock-in techniques are used to achieve high sensitivity. Tests in the laboratory have shown that the instrument is capable of detecting a very small relative absorbance of 10(-4)-10(-5) when integrating spectra for 1 s. The instrument is designed and qualified to resist the mechanical stress occurring during the start of a sounding rocket and to be operational during the cruising phase of the flight when accelerations are very small. Two almost identical versions of the MASERATI instrument were built and were launched on sounding rockets from the Andøya Rocket Range (69 degrees N) in northern Norway on 12 October 1997 and on 31 January 1998. The good technical performance of the instruments during these flights has demonstrated that MASERATI is indeed a new suitable tool to perform rocket-borne in situ measurements in the upper atmosphere.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.