Scientific Results

Real-time monitoring of volcanic emissions with a laser-based fiber spectrometer

Year: 2004

Authors: Rocco A., Gagliardi G., Gianfrani L., De Natale G., De Natale P.

Autors Affiliation: Istituto Nazionale di Ottica Applicata, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy;
Dipartimento di Scienze Ambientali, Seconda Universita’ di Napoli, Via Vivaldi 43, 81100 Caserta;
INGV – Osservatorio Vesuviano, Via Diocleziano 328, 80124 Naples, Italy

Abstract: Recent progress in telecom-based optoelectronic devices and low power laser sources has provided new powerful tools for in-situ monitoring of volcanic areas in real-time and for long periods, with unprecedented accuracy and resolution. Such techniques represent a great improvement if compared to the traditionally used “in-situ” sampling techniques such
as gas chromatography and mass spectrometry which result often impractical or dangerous, and do not allow temporally continuous monitoring. Optical communication diode lasers, which emit visible and IR radiation with mW power, operating on single mode at room temperature, are ideal sources to develop high sensitivity gas analysers based on absorption spectroscopy techniques. Their possible use in conjunction with fiber components is particularly advantageous in the perspective of developing networks for simultaneous monitoring of many geochemical and geophysical parameters. We report on the field tests of a novel Portable Diode Laser Spectrometer (PDLS), operating at a wavelength of 1.99µm and based on direct absorption spectroscopy, for high precision, accurate and real-time, simultaneous measurements of CO2 and H2O concentrations. We used an open-path configuration, positioning the detection bench, equipped with a a Herriott cell especially designed for measurements in hazardous environment, at different sites of the fumarolic areas. With such a configuration we can take advantage of the long optical path-length allowed by the multiple-pass cell (20.3m). The measured CO2 and H2O concentrations vs. time are shown.


Volume: 5459      Pages from: 259  to: 265

KeyWords: diode laser; absorption spectroscopy;
DOI: 10.1117/12.545808

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