Pasqualino Gaudio

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.

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.

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.

CO2 LASER BASED MOBILE DIAL SYSTEM FOR ATMOSPHERIC POLLUTANTS MONITORING

Abstract There are different techniques of remote sensing, with the dial has been obtaining good results to achieve concentration profiles of several pollutants. In fact, it allows to evaluate the remote concentration of atmospheric constituents. In particular a good tools for this purpose are the dial systems based on CO 2 laser which can be used routinely having an high degrees of eye safety. At the Department of Physics of the University of Calabria a lidar-dial land system has been developed and on the basic of that we have realised a prototype of a mobile station. In the system there are mounted two home-made twin TEA CO 2 lasers in SFUR configurations. The receiving system is based of a cassegrain telescope with 40 cm of diameter that acquire the backscattered signal and on the focal plane is located a cooled HgCdTe detector. The signal is acquired by VXI system and stored in a memory of a personal computer. The laser pulse is transmitted and received by a scanner module The system is mounted in a container which can be transported. At the aim to test the fixed station was done measurements on an horizontal path to span with the laser beam over both a large urban area and a rural one. Work is in progress to improve the mobile dial system in order to have better performances and to achieve atmospheric profiles of compounds of environmental interest .

Absorption measurement with CO2 lasers for atmospheric studies

Between the different techniques of remote sensing the lidar-dial one has been obtaining more importance in achieving concentration profiles of several pollutants. In this paper we describe the system set up at the University of Calabria based on two CO2 pulsed lasers. In order to evaluate the amount of the pollutants it is necessary the knowledge of the related absorption coefficients. These have been measuring since most of them are not present in the literature. As example the calibration measurements taken on CFC11 are presented after a brief remark of the theory applied. Beside this work preliminary concentration profiles of water vapor and ozone along an horizontal path obtained with the dial system are showed and discussed.

Water vapor and ozone profiles with a CO2 dial system in South Italy

In this paper we present the work carried out at the University of Calabria regarding a prototype of a dial system. This has been realized for remote pollution monitoring. Most of the effort have been done to perform several measurements on an horizontal path in order to scan the wide surrounding area. The concentrations of ozone and water vapor have been carried out using two different methods both related with the dial technique. With the integrated one average concentrations have been evaluated up to 5 km using topographical targets. In the range resolution technique profile of ozone and water vapor have been performed up to 700 m with a spatial resolution of about 30 m. Although the system needs a revision in several subsystem of its set up, the experimentation has pointed out the performances available and the necessary improvements.