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Air Monitoring by Infrared Laser

#1113-2


Ecological Monitoring in the Sites of Chemical Weapons Destruction and Near High-Danger Industries by the Multifrequency Infrared Laser

Tech Area / Field

  • ENV-MIN/Monitoring and Instrumentation/Environment
  • ENV-APC/Air Pollution and Control/Environment

Status
8 Project completed

Registration date
13.07.2000

Completion date
18.11.2005

Senior Project Manager
Kulikov G G

Leading Institute
Institute of Problems of Chemical Physics, Russia, Moscow reg., Chernogolovka

Supporting institutes

  • VNIIEF, Russia, N. Novgorod reg., Sarov\nRussian Scientific Center of Applied Chemistry, Russia, St Petersburg

Collaborators

  • New Mexico State University, USA, NM, Las Cruces\nCNRS/Universite Claude Bernard-Lyon 1/Laboratoire de Spectrometrie Ionique et Moleculaire, France, Lyon\nScience Applications International Corporation, USA, VA, McLean\nJoint Research Centre / Institute for Systems Informatics and Safety, Italy, Ispra\nBattelle Memorial Institute, USA, OH, Columbus\nScientific Utilization Inc., USA, AL, Huntsville

Project summary

At present various lidar systems unravel many tasks related to atmosphere studies. Nevertheless, some problems remain unsolved or solved unsatisfactorily, in particular the problem of remote determining aerosol chemical composition and concentration, especially of chemical agents and of discharges from dangerous chemical and radiation industries including crash situations.

Aerosol recognition, i.e. identification of aerosol substance and determination of concentration and sizes of aerosol particles, could be based on using the so-called spectral resonances recorded in the region of absorption bands of aerosol substance, where intensity of backscattered radiation undergoes significant (up to two orders of magnitude) non monotonous variations. Position and shape of the spectral resonance are inpidual peculiarities of the substance, the shape depending on sizes of particles also. Thus, distant backscattering spectrum recording could allow recognizing aerosol admixtures remotely. It could be accomplished with the aid of tuned or multifrequency laser source emitting in proper spectral range.

First stage of the project (ISTC Project #1113, “Ecological monitoring using multifrequency IR laser. Mathematical modelling and feasibility study”) was summarized in accompanying Summary Report. As a result of its execution, the following items are analysed in detail and formulated.

Project purpose: Remote determination of chemical composition and content of gaseous and aerosol atmospheric admixtures (including highly dangerous substances and chemical agents) by the analysis of aerosol backscattered multifrequency laser radiation in the spectral range of atmospheric transparency window from 3 to 5m.

Methodology: The revelation of spectral resonances in aerosol backscattering with the aid of multifrequency response obtained on 20-30 laser sounding lines. Gaseous admixtures are to be determined according to known methodology of differential absorption developed for the conditions of background aerosol backscattering.

Recognition principle: Using genetic algorithm for interpretation of multifrequency backscattering response with the aid of data bank information on aerosol scattering and gaseous absorption for inpidual substances.

Technical solution: Lidar complex based on pulsed powerful chemical HF/DF laser initiated by chain reaction. The needed most significant laser characteristics and expected lidar complex performances are shown in the Table.

total pulse energy and power

300 J, 108 W

number of concurrently radiated lines needed for recognition

>20

radiation energy per line

>0.3 J

recognition threshold for aerosol with size of particles from 3 to 100m

10-8-510-7 g/l

minimum detectable concentration of gaseous admixtures (dependent on absorption cross section)

4ppb·km - 40ppm·km

estimated range of detection

~10 km.

The lidar complex to be developed in the course of the project has no analogs as to the stated purpose and the ways of attaining it and, therefore, will be the new step in the environmental studies and ecological monitoring.

Project participants are the specialists in the fields of powerful chemical lasers and laser spectroscopy, of atmospheric optics and complicated optical systems, of chemical warfare monitoring and information treatment including creation of recognition software.

Planned second stage working schedule includes basic studies, elaboration and production of lidar prototype, and its trial demonstration.

Main expected basic result of the project. The scientific fundamentals for remote recognition of gaseous and aerosol atmospheric admixtures will be substantiated in the course of project execution. The recognition is based on the revelation and interpretation of spectral resonances in aerosol backscattering of multifrequency sounding radiation that will be ensured by the following project issues:

1. Spectral information interpretation algorithm based on evolution and genetic method.

2. Additional a priori recognition criteria for speeding up computations and improving recognition authenticity.

3. Spectra of aerosol backscattering and gas absorption for substances, which are of special topicality in atmospheric pollution analysis, namely organic compounds containing nitrogen, chlorine, fluorine, and phosphor.

4. Study of emission spectrum energy distribution for concurrent HF and DF lasing aimed at optimized conditions for sounding and recognition.

As a result of all these achievements, new level of knowledge needed for solving problems of ecological safety and environmental control will be attained.

Basic results planned within the framework of the project are applicable more widely as compared to project statement, especially the outcomes of recognition procedure development, which could be used for other lidar types and also for other recognition problems.

The elaborations planned to be executed within the framework of the project will lead to the creation of the lidar prototype including:

1. Multifrequency laser radiator with all branch systems.

2. Receiving system for gathering backscattered radiation, spatial resolution of its spectral components and their detection.

3. Multichannel recording system (20 channels) for signal amplification, digitizing, storing, and transfer to computer (for subsequent processing).

As far as we know, at present there are no analogs in the world of the lidar complex to be elaborated.

Trial demonstration will be carried out in the testing area of IPCP RAS (Chernogolovka). The lidar complex will be installed in a van, and the aerosol cloud to be recognized will be represented by its simulator (aerosol chamber). In the course of the testing lidar complex, its abilities for detection and recognition of atmospheric admixtures will be verified.

Based on created lidar prototype, the following design elaborations and perse studies will be possible:

- elaboration of a preproduction prototype of mobile lidar complex with recruiting R&D organizations;

- studies leading to improved lidar performances, such as detectability, long range, the sphere of recognized substances, etc.;

- studying the feasibility of sounding upper atmospheric layers;

- studies related to possible substitution of HF/DF laser by another type of radiator in the same spectral range.

It is to be noted here that at present we do not see an alternative to chemical laser as to the spectral and energetic performances (the number of simultaneously emitted lines in suitable spectral range and resources of power increasing).

As a result of project realization, the group of scientists from IPCP RAS in Chernogolovka, Moscow region, RFNC VNIIEF in Sarov, RSC "Applied Chemistry" in St.Petersburg and also invited from State Science Center “Scientific and Production Association “Astrophysika”” and Military University of Radiation, Chemical and Biological Defence in Moscow will be reorientated to solving actual problems of ecological safety. These specialists were engaged in works on creation of missile and nuclear weapons and also of special purpose laser complexes.

Proposed project will undoubtedly conductive to basic and applied studies and also to elaborations in the field of science intensive techniques of atmospheric monitoring.

The following volume of cooperation with foreign collaborators is supposed:

- reviewing the Work Plan;

- reviewing the annual and final reports:

- discussion of the testing schedule and participation in testing;

- participation in joint seminar.

Obtaining data on chemical composition and contents of atmospheric admixtures is based on the method of multifrequency laser spectroscopy, necessary spectral information receiving in single radiation pulse of multifrequency chemical laser of medium power.

Recognition procedure is based on evolution and genetic method developed for fast interpretation of gamma spectra in the course of isotope analysis of samples.

Accumulation of spectral data bank will be realized as follows:

- for aerosols, on testing facilities equipped with aerosol chamber, OPO, and recording system for backscattered radiation;

- for gases, by absorption measurements on HF/DF laser radiation lines;

- in both cases, from calculations and literature data.

Long-term unique experience of project participants related to designing and servicing chemical lasers and recording systems will be used on elaboration of lidar complex constituents.


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