Monte Carlo modeling of cavity imaging in pure iron using back-scatter electron scanning microscopy

Abstract

Backscattered electrons (BSE) in a scanning electron microscope (SEM) can produce images of subsurface cavity distributions as a nondestructive characterization technique. Monte Carlo simulations were performed to understand the mechanism of void imaging and to identify key parameters in optimizing void resolution. The modeling explores an iron target of different thicknesses, electron beams of different energies, beam sizes, and scan pitch, evaluated for voids of different sizes and depths below the surface. The results show that the void image contrast is primarily caused by discontinuity of energy spectra of backscattered electrons, due to increased outward path lengths for those electrons which penetrate voids and are backscattered at deeper depths. Size resolution of voids at specific depths, and maximum detection depth of specific voids sizes are derived as a function of electron beam energy. The results are important for image optimization and data extraction.

Experimental Evaluation of Deformation and Fracture Mechanisms in Highly Irradiated Austenitic Steels

“…Figure 2 shows the radiation-induced void structure, imaged using the SEM/backscattered electron (BSE) technique described in [10,11]. This technique allows the evaluation of large areas and detects strain-and dislocation channeling-induced changes.…”