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Eingeladener Vortrag
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In order to enhance the supply chain security at airports, the German federal ministry of education and research has initiated the project ESECLOG (enhanced security in the air cargo chain) which has the goal to improve the threat detection accuracy using one-sided access methods. In this paper, we present a new X-ray backscatter technology for non-intrusive imaging of suspicious objects (mainly low-Z explosives) in luggage's and parcels with only a single-sided access. A key element in this technology is the X-ray backscatter camera embedded with a special twisted-slit collimator. The developed technology has efficiently resolved the problem related to the imaging of complex interior of the object by fixing source and object positions and changing only the scanning direction of the X-ray backscatter camera. Experiments were carried out on luggages and parcels packed with mock-up dangerous materials including liquid and solid explosive simulants. In addition, the quality of the X-ray backscatter image was enhanced by employing high-resolution digital detector arrays. Experimental results are discussed and the efficiency of the present technique to detect suspicious objects in luggages and parcels is demonstrated. At the end, important applications of the proposed backscatter imaging technology to the aviation security are presented.
In the context of the German aviation security research and development project SILUFRA (secure air freight transport chains), BAM has developed a high-resolution and high-energy X-ray imaging technology for the reliable detection of dangerous and illicit materials in densely packed air freight containers. In the developed technology, a novel combination of high-energy (2-7.5 MeV) X-ray betatron as the radiation source and a high-resolution digital detector array (DDA) for the X-ray imaging was utilized to improve the probability of detecting contraband and explosive materials by enhancing the spatial and contrast resolution in the digital X-ray image. In addition, flexible rotations of the high-energy X-ray source and the digital detector array can lead to clarify the suspicious region of interest (ROI) in air freight containers efficiently. Thus, reduces the false alarm rates and the need for expensive manual inspections of the whole container load. In order to evaluate the detection efficiency, we carried out the experimental investigations on a real air freight container loaded with typical cargo materials such as heavy automobile components and electronic products as well as mock-up dangerous and contraband materials. Furthermore, the material discrimination in the radiographic images was evaluated based on the dual high-energy X-ray imaging method. Finally, important applications of the proposed imaging technology to the air cargo security are discussed
Radiologic evaluation techniques are nondestructive testing (NDT) used to detect the bulk of explosives and contraband materials in large objects. As compared to conventional low-energy (<450 key) X-ray imaging, high-energy (>1 MeV) digital X-ray radiography is required for the NOT of large containers because of the need for high penetration through thick materials, sensitivity, and the ability to distinguish between low-and high-Z materials. Mobile, high-energy, and high-resolution radiologic techniques are useful to detect contraband and threat materials in digital radiographic images of containers with complex packing. This paper presents a mobile, high-energy X-ray radiographic technique for the in-field nondestructive inspection of cargo containers. The developed experimental technique consisted of a betatron as a high-energy (7.5 MeV) X-ray source and a high-resolution (400 mu m) matrix detector for the digital X-ray imaging. In order to evaluate the detection efficiency and image quality of the measurement technique, a test specimen was proposed that was made of a 3 mm thick steel container with an inner dimension of 60 x 30 x 40 cm(3) comprising different low-and high-Z materials. Image quality indicators were used to assess the essential image quality parameters such as image basic spatial resolution, effective attenuation coefficient, and signal-to-noise ratio (SNR). Experimental investigations were performed on a 6.1 m sea freight container with mockup dangerous materials in complex packing. Preliminary experimental results showed that the proposed technique was able to distinguish between liquids and solids, as well as detect contraband materials. Furthermore, a remarkable SNR of 400 was achieved in the measured digital X-ray images. The influence of temperature on X-ray radiation dose rate at different X-ray energies was also investigated. Finally, important applications of the proposed technique in the context of maritime security are discussed.
This paper presents a new X-ray backscatter technique (XBT) for non-destructive imaging of aerospace materials with only a single-sided access. It uses a special twisted slit collimator to inspect the whole object 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 (>500 keV) X-ray sources. Experiments were performed on thick complex structured aluminium components, stringers and honeycomb structures to validate the applicability of the present technique to image small changes in the material properties and also to detect low-density material inclusions. In order to reduce the inspection time from hours to several seconds and to improve the image quality of the X-ray backscatter image, the backscattered signals were measured using a digital detector array with high spatial resolution (200 µm). The influence of the energy of the X-ray source and the slit width of the camera on the X-ray backscatter image were also investigated. In the proposed technique, the whole object is irradiated by an un-collimated X-ray beam resulting in a low image acquisition time of 3 min that facilitates the use of XBT for the real time NDT&E of aerospace materials.
A comparative study on the performance of digital detector systems for high energy applications
(2014)
For cast components reaching or exceeding total material thicknesses of 150mm, high energy sources such as linear accelerators or Betatrons are required in order to obtain reasonable exposure times. In this study, the performance of digital detector systems, involving imaging plates (IP) and digital detector arrays (DDA), was evaluated with respect to the testing class B requirements as formulated in the standard EN ISO 17636-2. As a reference, traditional radiographic film and a Cobalt-60 source was used. With film exposures, testing class B was achieved with Co-60 and Betatron (7.5 MV) at longer exposure times. The preliminary results show that the testing class B was not obtained with the examined digital detector arrays (DDA) and the high resolution imaging plates (IP) , even at 40, 60 and 80 minutes exposure time with a 7.5 MV Betatron. Class A was achieved using high resolution imaging plates with optimized metal filters between object and IPs and a high resolution DDA with intermediate Cu filters. Class A was also achieved applying a DDA with lower basic spatial resolution than required by Table B.13 of EN ISO 17636-2, but using the compensation principle as described in this standard. The next generation of digital detector arrays might potentially be able to obtain class B performance with the expected spatial resolution and sensitivity improvements.
The objects of this investigation were sculptures taken from a ca. three hundred years old baroque epitaph of a church in Tonning, a town in Northern Germany. Around 1900 it was found in a disastrous state heavily damaged by wood-worm. At that time, the whole artwork was treated with the tar extract carbolineum as a remedy. Nowadays, this substance has been identified as carcinogenic, and its presence can be perceived by its stench and visually at certain spots on the surface where it has penetrated the covering paint.
A gold-painted sculpture of a massive wooden skull was interrogated with X-rays and fast neutrons to investigate the internal distribution of the carbolineum. The X-ray tomography, with its excellent spatial resolution revealed galleries left over from the worm infestation in the outer areas and cracks in the central region. The golden color coating appeared as a thick and dense layer. In comparison the tomography with fast neutrons, though being of lower resolution and yet unresolved artefacts revealed sections of slightly different densities in the bulk of the wood. These differences we attribute to the differences in the distribution of the impregnant in the wood, visible due to its higher hydrogen content making it less transparent for neutrons.
Innovative X-ray backscatter technique for security applications: Detection of dangerous materials
(2014)
Radiological inspections, in general, are NDT&E methods to detect the bulk of explosives without invasion into the object of analysis. In contrast to personal luggage, cargo or structural components constitute a complexity that may significantly hamper the detection of a threat by conventional transmission radiography. A novel approach of interrogating a large object to a certain depth only with a single sided access will be presented. It consists of an X-ray backscatter camera with a special twisted slit collimator for imaging backscattered objects. The new X-ray backscatter camera is not only imaging the objects due to their densities but also by taking into account the influences of surrounding objects. Additionally, it does not only image illuminated features but also depicts shadows from absorbing materials. This is a unique characteristic of the developed X-ray backscatter camera. Experimental mock-ups are conducted imitating container with threats among a complex packing as they may be encountered in reality. At the end, the significant advantages of the presented X-ray backscatter camera in the context of aviation and port security will be discussed.
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.