Wissenschaftliche Artikel der BAM
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In this contribution, we present a dual high-energy X-ray imaging technique for cargo container inspection using the 'spectral high-energy X-ray attenuation method'. This method is based on attenuation of continuous highenergy spectra. The developed experimental technique consists of a betatron as high-energy (up to 7.5 MeV) X-ray source and a matrix detector with high spatial resolution (400 ìm) for digital X-ray imaging. In order to evaluate the material discrimination capability using dual high-energy X-ray imaging, a test specimen is proposed, comprising step wedges of different low and high atomic number (Z) materials. The selected X-ray spectra for the dual-energy experiments correspond to 3 MV and 7.5 MV acceleration potential of the betatron. We evaluated the ratio between low- and high-energy X-ray attenuation coefficients quantitatively based on simulated poly-energetic high-energy X-ray source spectra and the detector sensitivity using the 'analytical Radiographic Testing inspection simulation tool' (aRTist) developed at BAM. The simulated effective attenuation coefficients are compared with corresponding experimental results in order to establish a method for identification of low- and high-Z materials in the container. Finally, important applications of the proposed technique in the context of aviation security are discussed.
Critical parts in aircraft manufacturing such as stringers are very commonly used in modern aircraft structures to resist the compressive loads caused by the aerodynamic effects. They are generally made-up of thin aluminium (Al) metal sheets and are one of the key components in the aircraft wings. Any defects in the stringer leads to weakening of the stiffness of the whole wing structure and consequently, failures may occur. Hence, the structural integrity of the stringers should be evaluated using reliable non-destructive testing (NDT) methods. Due to the complex shaped structure of the stringer, the one-sided access NDT method such as X-ray backscatter technique is more preferable for the non-destructive imaging. In this paper, we present a new X-ray backscatter technique to image the internal sections of the stringer with only a single-sided access. The whole object was inspected by changing the viewing direction of the X-ray backscatter camera. For the first time, the X-ray backscatter measurements were conducted using high-energy (> 0.5MeV) X-rays and proved the applicability of the present technique to inspect thick carbon-fiber laminated components. In order to improve the inspection time and image quality of the backscatter image, we used high-resolution (180ìm) digital detector arrays (DDAs). At the end, important applications of the presented X-ray backscatter technique to the aerospace industry are discussed.