Bulg. J. Phys. vol.34 no.s1 (2007), pp. 333-348



Gamma-Ray Lidar (GRAYDAR) in-Depth Sensing of Optically Opaque Media

L.L. Gurdev1, T.N. Dreischuh1, D.V. Stoyanov1, Ch.N. Protochristov2
1Institute of Electronics, Bulgarian Academy of Sciences, Tsarigradsko Chaussee 72, BG-1784, Sofia, Bulgaria
2Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Tsarigradsko Chaussee 72, BG-1784, Sofia, Bulgaria
Abstract. Recently we proposed and investigated the feasibility of a novel approach for gamma-ray single-sided in-depth sensing and tomography of dense optically opaque media. The approach is based on graydar (Gamma RAY Detection And Ranging) principle, that is, time-to-range resolved detection of the backscattering-due radiative returns from the probed object irradiated by pulsed gamma-photon pencil beams. It was shown analytically and by simulations that under Poisson noise conditions such an approach would enable one, at reasonable sensing-photon fluxes and measurement time intervals, to accurately determine the location, the material content, and the mass density of homogeneous ingredients within homogeneous surroundings as well as the mass (or electron) density distribution within one-material objects. At the same time, being quite general, the idea of graydar sensing should have considerably wider applied potential. In the present work we make a step to extending our knowledge about the applicability of the graydar approach. Concretely, we have investigated by simulations based on some theoretical reasons the possibility of detecting and characterizing homogeneous one-material ingredients in one-material surroundings with non-uniform spatial density distribution. As a result it is shown that one may find, locate and recognize, without noticeable shadowing effect, homogeneous one-material objects with relatively low contrast (say, the components of plastic landmines) hidden in one-material medium (say, soil) with strongly spatially varying density.

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