Carlo Bellecci

CO2 dial for monitoring atmospheric pollutants at the University of Calabria

SummaryIn this report we introduce the infrared lidar-dial apparatus developed at the University of Calabria. It has been carried out as a tool in the investigation of both the atmospheric pollution of trace gases and other atmospheric parameters as water vapour. The general scheme of the station is described, as well as the performances of the home-made CO2 laser sources. Finally preliminary measurements of average concentration of ozone and water vapour over a range of about 3 km are presented and discussed in the report.

Effect of the differential geometric form factor on differential absorption lidar measurements with topographical targets

When the integrated differential absorption lidar (DIAL) technique is used to perform concentration measurements over long distances, the alignment between on and off laser beams becomes important. Here, through analysis of alignment error and of the corresponding differential geometric form factor, the effect of misalignment between off and on lines on performance of integrated concentration measurements by a coaxial DIAL system is considered.

Plasma shutter for CO2 TEA laser for high-range resolved mapping of chemical plume

A plasma shutter has been made for cutting nitrogen tail of energy pulse of TEA CO2 laser. Studies to implement all set-ups has been done using preliminarily a TE CO2 laser source. The system is described and the dependence of the gas break down by energy of the discharge is discussed.

Improvement of Calabria University CO2 laser DIAL system

Comparison between theoretical previsions on the backscattered signals and experimental ones have indicated some disagreements which led to a revision of the optical receiver system of the carbon-dioxide laser dial equipment. A new telescope has been set up as well as an optical system designed to control routinely the alignment, and, the overlapping among the telescope optical axis and the laser beams.

TEA CO/sub 2/ Dial Station for Atmospheric Water and Pollutants Measurements

C. Bellemi. P. Gaudio, M. Valentini INFM Dcpamncnr of Physics, Univeniw of Calabria, 87036 Arcavacata di Rsndc (CS); tel.: -39 984 401741: fax t i 3 9 984 401660 s-mail: hsl lecssi~or.uniraI. i l S. Martellucci INFM STFE Dcpamncnfunivosity o f R,701 Vergal’. 00133 Rome: el.: +39612597144, fax: +t3?6 7 2 5 9 7 I 4 S : o m d l r m ~ v r m . i l P. Avma, G. Caputi, F. De Donato R. Zoccali CRATl ~ . ~ . r . l . u o Depamnmr ofPhyncr, univenily ofCrlaMa, 81036 AICBYBCBI~ di Rende (CS); Lel.:++?9984838053 -83t052;fax:+b39984401660

TE-CO/sub 2/ Injection Laser: Satus and Perspectives

C. Bellemi. P. Gaudio, M. Valentini INFM Dcpamncnr of Physics, Univeniw of Calabria, 87036 Arcavacata di Rsndc (CS); tel.: -39 984 401741: fax t i 3 9 984 401660 s-mail: hsl lecssi~or.uniraI. i l S. Martellucci INFM STFE Dcpamncnfunivosity o f R,701 Vergal’. 00133 Rome: el.: +39612597144, fax: +t3?6 7 2 5 9 7 I 4 S : o m d l r m ~ v r m . i l P. Avma, G. Caputi, F. De Donato R. Zoccali CRATl ~ . ~ . r . l . u o Depamnmr ofPhyncr, univenily ofCrlaMa, 81036 AICBYBCB(. di Rende (CS); Lel.:++?9984838053 -83t052;fax:+b39984401660

TE-CO2 injection laser : Status and perspectives

Within the framework of our LIDAR activity devoted to air pollution measurements, we realized the injection of a continuous carbon dioxide laser into a high power TE CO2 laser, to get the possibility of better analyze return signal response and to realize a Doppler wind velocimeter. Apart from the need of temporally smooth pulse to examine measurements result, in remote sensing it is desirable to use narrow band laser sources. The request of high spectral performances is manly based on the possibility to use heterodyne detection, on one hand, to improve the signal to noise ratio, and, on the other, to observe and analyze Doppler frequency shift in the return signal. We are engaged into implement a TE CO2 laser source by injection of a cw pulse from a low pressure CO2. Preliminary results we obtained show a smoothing of the output pulse shape and a consequent reduction in spectral band-width, revealing a single longitudinal mode operation.

Comparision of water vapor measurements made with TEA CO2 lasers using different laser line couples

We have designed, developed and constructed a CO2 laser based LIDAR-DIAL field tested with preliminary measurements of concentration of water vapor two. Two years we have developed this preliminary measurements using alternatively the R20 and R18 lines in the branch at 10 micron of two twin CO2 lasers and we have obtained the density profile on a long path of about 800 m. At present the maximum range of the lidar signal on the absorption line is limited by dynamic range and the NEP of our detector. To extend the range of lidar signals a theoretical work has been done about the use of new laser lines for range resolved measurements of water vapor for distance of 1 km. In fact the absorption coefficient of the on-line 10R20 is very strong and the lidar signal for range up to 1 km is obscured by noise of the detector. The theoretical work already gave a good results and presently we are making the experimental measurements to compare with the theoretical data.

First measurements of water vapor and ozone with TEA CO2 lasers to test lidar station

A CO2 laser-based DIAL system has been developed for mapping vapor plumes. The DIAL system is composed of two home-made twin TEA CO2 lasers in self filtering unstable resonator. The receiving system is based on a Newtonian telescope with a 40 cm diameter that acquires the backscattered signal with a cooled HgCdTe detector on the focal plane. The signal is acquired by a VXI system and stored in the memory of a personal computer. The laser pulse is transmitted and received by a scanner module. Our first measurements indicated some disagreement between theory an practice. To resolve these problems in our fixed station we had to modify many aspects relating to the optical emission and performance of the station. The measurement have been made on water vapor and ozone. After a careful study of the experimental result we have decided to build a mobile lidar station.

TE - CO2 INJECTION LASER FOR WIND MEASUREMENTS DOPPLER APPLICATION

Abstract Within the framework of our LIDAR activity [ 1 ] devoted to air pollution measurements, we realised the injection of a continuos carbon dioxide laser into a high power TE CO2 laser, to get the possibility of better analyse return signal responses and to realise a Doppler wind velocimeter [ 2 ], [ 3 ]. Apart from the need of temporally smooth pulse to examine measurements results, in remote sensing it is desirable to use narrow band laser sources. The request of high spectral performances is mainly based on the possibility to use heterodyne detection, on one hand, to improve the signal to noise ratio, and, on the other, to observe and analyse Doppler frequency shit in the return signal. We are engaged in to implement a TE CO2 laser source by injection of a cw pulse from a low pressure CO2 into a TE. Preliminary results we obtained show a smoothing of the output pulse shape and a consequent reduction in spectral band-width, revealing a single longitudinal mode operation.