Zastosowanie laserów kaskadowych do wykrywania śladowych zanieczyszczeń gazowych atmosfery

Spektroskopowe systemy detekcji gazów, w których jako źródła promieniowania IR wykorzystuje się kwantowe lasery kaskadowe, są coraz powszechniej wykorzystywane do monitorowania poziomu zanieczyszczenia atmosfery gazami przemysłowymi. W pracy omówiono system wykrywania i monitorowania poziomu amoniaku w atmosferze. System charakteryzuje się dużą czułością umożliwiającą wykrywanie i monitorowanie amoniaku o stężeniu w powietrzu na poziomie pojedynczych ppb.

Spectroscopic gas detection systems, in which quantum cascade lasers are used as IR radiation sources, are increasingly being applied to monitoring the level of air pollution by industrial gases. These systems allow the detection and long-term monitoring of toxic gases in the atmosphere, the minimum concentration of which may be equal to a single ppt. The paper describes a system capable to detect and monitor the level of ammonia in the atmosphere. In this measuring system the advantages of a quantum cascade laser and spectroscopic detection methods are combined. Its main components are: a quantum cascade laser and a multipath cell. Operation of the system is exemplified by monitoring the natural level of ammonia in the ambient air. The paper presents the advantages of using cascade lasers in detection systems of gaseous pollutants. The first section discusses the construction of the system and presents the block diagram (Fig. 1). The second section contains the results of the studies of natural concentration of ammonia in the ambient air (Fig. 3). Based on these results, it was found that the system has a high sensitivity sufficient to detect a concentration of ammonia in the air at the level of individual ppb. It also allows continuous, long-term monitoring of the concentration of this gas in the air. The sensitivity of the system depends mainly on the optical path used in the multiple-pass cell and the power of the cascade laser beam.