Gas concentration measurements with DFB lasers to monitor volcanic activity

We report construction and operation of a multiplexed laser spectrometer, based on fiber coupled Distributed Feed-Back (DFB) semiconductor diode lasers, for monitoring concentration of gases emitted from volcanoes. The main problems related to this particular application, as well as the way of operation of the apparatus are discussed. The first experimental data, recorded at the test site of Solfatara volcano, Naples, Italy are reported. To our knowledge, this is the first design of a small, low power consuming laser spectrometer for geochemical applications.