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Remote Detection of Radioactivity

#0660


Development and Test of an Optical System Prototype for Radioactivity Source Remote Detection

Tech Area / Field

  • ENV-MIN/Monitoring and Instrumentation/Environment

Status
3 Approved without Funding

Registration date
28.05.1996

Leading Institute
Passat (Private Company), Russia, N. Novgorod reg., N. Novgorod

Supporting institutes

  • VNIIEF, Russia, N. Novgorod reg., Sarov

Collaborators

  • Los-Alamos National Laboratory, USA, NM, Los-Alamos\nLockheed Martin Corporation / Bechtel BWXT Idaho / Idaho National Engineering Laboratory, USA, ID, Idaho Falls

Project summary

The project objective is a creation of a lidar and measurement technique providing a remote detection of radioactive sources. Such a detector is necessary to check out a maintenance of the nonproliferation regime and prevent actions of nuclear terrorists. Besides, the proposed system would be very useful at nuclear accidents.

An operation of the lidar to be developed is based on a detection of areas characterized by an increased concentration of substances produced in a process of radiolysis, i.e., an interaction of radioactive radiation with atmosphere. At present only contact techniques of monitoring are widely used. The task is solved with a net of fixed radiometer stations distributed over a controlled area or with moving (portable) radiometer units. The first practice requires essential capital investments but does not permit high spatial resolution measurements. The second method needs a long time for measurements and sometimes results in extra-exposure to radiation for operating personnel.

A specific feature of the proposed system is an operation within the mid-IR range (6-12 mm). It is well known that an absorption of radiation is quite low in this range. Thus, one can expect a sufficient advantage in a distance range in comparison with lidars operating at the visual and UV ranges. Besides, in the frameworks of a preliminary investigation it was shown that the proposed optical scheme of the detection unit based on the new Raman Enhanced Four Wave Mixing technique provides an extremely high sensitivity and, consequently, a record-breaking distance range. Another merit of the scheme is an opportunity to tune an operational wavelength within a broad range, keeping a narrow radiation line (the line width does not exceed 0.1 cm-1). It allows to detect different substances (ozone, NO, etc.) created as a result of an air-radiation interaction. Preliminary estimations have shown that such substances of a concentration up to 100 ppb may be detected at distances of a few hundred of kilometers. Finally, the mid-IR range is eye-safe, permitting to carry out measurements in thickly populated environments.

Two main problems must be solved within the frameworks of the project. Firstly, it is necessary to study a dependence of a concentration of excess ozone and other radiolysis products on radiation parameters. Basing on this study, a monitoring technique should be developed.

The second problem is connected with a development, fabrication, and testing of the lidar. It is supposed that the lidar should consist of three main units. The master oscillator based on an Nd:YAG laser is used as a pump source. This source delivers an input radiation to a two-stage frequency converter. The converter is composed of an optical parametric oscillator and Raman cell. It transforms a laser radiation of 1064 nm wavelength to a radiation tunable within a range of 6-12 mm. The Raman cell is used also as a detector of a quantum sensitivity. The lidar will operate at a pulse repetition rate of 2 Hz, the pulse energy being 30 mJ. The diffraction beam pergence should be provided. According to preliminary estimations, the maximum distance of operation may achieve 1000 km.

From the fundamental point of view, the project will result in new data concerning the process of interaction between atmosphere and radioactive radiation. Besides, an experimental research of the Raman Enhanced Four Wave Mixing will be carried out.

As for commercial merits of the Project, a development of a wide-range lidar will allow to propose similar schemes for using in other fields. At present Passat Enterprise takes part in a creation of a lidar operating at a wavelength range of 8-12 mm. This work is carried out according to a contract with INEL (USA). Another contract is being discussed. In the frameworks of the new contract Passat Enterprise and VNIIEF should widen a wavelength range to provide detection of some substances used in manufacturing chemical weapons. It should be noted that the optical parametric oscillator and Raman converter to be included in the lidar developed according to the present proposal have been created and tested already as a part of the lidar created for INEL.

Los Alamos National Laboratory is interested in the Project and will take part in it as a collaborator. LANL will take responsibility for reviewing and advising this Project. The final tests of the system prototype may be carried out at LANL facilities.


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