The measurement of the wall thickness of steel sections using Compton backscattering

Abstract

The use of Compton backscattering for the contactless measurement of the thickness of steel sections and similar dense materials up to 25 mm thick, when access is available only from one side of the sample, has been investigated. The expected intensity of back-scattered photons in a Compton thickness gauge has been estimated using a simple model, whose predictions have been verified and extended by the use of the GEANT3 Monte Carlo package which allowed the scattering geometry to be modelled accurately and the effects of multiple scattering to be estimated. The simulations have been confirmed by experimental measurements on steel samples 1-45 mm in thickness. With a 5 Ci 60 Co radioactive source, a rapid, reliable measurement of wall thickness can be obtained with steel samples up to 20 mm thick, but for thicker samples the absorption of backscattered photons limits the accuracy that can be achieved.

Gamma-Ray Backscattering Tomography Approach Based on the Lidar Principle

“…According to the quantitative definition of extinction coefficient, we have obtained below expressions of and concerning the cases of monoatomic and polyatomic substances. So, for monoatomic substances we have (9) where , and [m ] is a total atomic cross section taking into account all essential processes of absorption and scattering leading to photon losses from a beam. Such essential processes that are usually taken into account are [17] photoionization, coherent Rayleigh scattering, incoherent Compton scattering (including radiative corrections and double Compton effect), electron-positron pair production in the Coulomb field of the nuclei, and triplet production (of two electrons and one positron) in the field of the atomic electrons.…”

“…That is, the return signal profile detected in the time domain contains range-resolved information about the radiation-matter interaction (absorption and scattering) processes and the related material characteristics along the LOS. The "time-to-range-resolved" (lidar-type) approach for profiling physical media could be advantageous for various applications where single-sided sensing is required (e.g., [6]- [9]). In such cases, by irradiating the investigated object and detecting the scattered radiation from only one accessible side and laterally scanning the LOS, one can obtain three-dimensional (3D, tomographic) images of the object.…”

“…Therefore, being connected with these processes, the radiative response of an object irradiated by gamma or X rays should in general contain information about the material components and their disposition and mass density within the object. Certainly, this fact underlies various single-sided high-resolution non-destructive characterization techniques [6]- [9], [18]- [26] for gamma or X ray sensing and tomography of material substances that are not transparent for optical or microwave radiation. These methods are usually based on the dependence of the energy of the Compton single-scattered photons on the angle of scattering.…”

Use of Compton Back Scattering Technique for Detection of Corrosion in Pipes

“…The (NDT) technique investigated in present work is gamma backscattering method for detecting corrosion in the pipeline, because it has the following features attractive for on -site structural crack detection: (1) It is a nondestructive and non -contact method; (2) It can detect a crack below the surface; (3) It is not susceptible to surface roughness and material properties, except their densities; and (4) The source and detector can be located on the same side of the object, enabling testing of massive extended structures [4] . Asa'd (1997) [5] measuring the wall thickness of steel sections also by Compton backscattering. Khiem and Khai (2000) [6] developed a MonteCalro simulation to describe the interaction processes of gamma rays when coming in a medium and register the backscattered events are used to reproduce the shape of defects existing in the testing material, whereas Sheng (2002) [7] used the same method to detect the buried landmines.…”

The effect of an external electric field on radiation transmission and Compton scattering in plexiglass

“…where q is the density of the material, N a the Avagadro number, Z the atomic number and A the atomic weight of the scatterer [2]. Mazarakiotis et al [3] examined the electronic momentum density of polyethylene, one of the simplest polymers, with Compton scattering experiments.…”