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This work compares two popular MC simulation frameworks ROSI (Roentgen Simulation) and GEANT4 (Geometry and Tracking in its fourth version) in the context of X-ray physics. The comparison will be performed with the help of a parameter study considering energy, material and length variations. While the total deposited energy as well as the contribution of Compton scattering show a good accordance between all simulated configurations, all other physical effects exhibit large deviations in a comparison of data-sets. These discrepancies between simulations are shown to originate from the different cross sectional databases used in the frameworks, whereas the overall simulation mechanics seem to not have an influence on the agreement of the simulations. A scan over energy, length and material shows that the two parameters energy and material have a significant influence on the agreement of the simulation results, while the length parameter shows no noticeable influence on the deviations between the data-sets.

Conference of 50th Annual IEEE International Carnahan Conference on Security Technology, ICCST 2016 ; Conference Date: 24 October 2016 Through 27 October 2016; Conference Code:125934; International audience; Customs administrations are responsible for the enforcement of fiscal integrity and security of movements of goods across land and sea borders. In order to verify whether the transported goods match the transport declaration, X-ray imaging of containers is used at many customs site worldwide. The main objective of the research and development project 'Automated Comparison of X-ray Images for Cargo Scanning (ACXIS)', which is funded by the European 7th Framework Program, is to improve the efficiency and effectiveness of the inspection procedures of cargo at customs using X-ray technology. The current inspection procedures are reviewed to identify risks, catalogue illegal cargo, and prioritize detection scenarios. Based on these results, we propose an integrated solution that provides automation, information exchange between customs administrations, and computer-based training modules for customs officers. Automated target recognition (ATR) functions analyze the X-ray image after a scan is made to detect certain types of goods such as cigarettes, weapons and drugs in the freight or container. Other helpful information can also be provided, such as the load homogeneity, total or partial weight, or the number of similar items. The ATR functions are provided as an option to the user. The X-ray image is transformed into a manufacturer-independent format through geometrical and spectral corrections and stored into a database along with the user feedback and other related data. This information can be exchanged with similar systems at other sites, thus facilitating information exchange between customs administrations. The database is seeded with over 30'000 examples of legitimate and illegal goods. These examples are used by the ATR functions through machine learning techniques, which are further strengthened by the information exchange. In order to improve X-ray image interpretation competency of human operators (customs officers), a computer-based training software is developed that simulates these new inspection procedures. A study is carried out to validate the effectiveness and efficiency of the computer-based training as well as the implemented procedures. Officers from the Dutch and Swiss Customs administrations partake in the study, covering both land and sea borders.

International audience; Customs continue to use a wide range of technology in protecting against terrorism and the movement of illicit trade and prohibited imports. The throughput of scanned vehicles and cargo increases and just keeps on growing. Therefore, the need of automated algorithms to help screening officers in inspection, examination or surveillance of vehicles and containers is crucial. In this context, the successful collaboration between manufacturers and customs offices is of key importance. Facing this topic, within the seventh framework program of the European Commission, the project ACXIS “Automated Comparison of X-ray Images for cargo Scanning” arose. This project develops a reference database for X-ray images of illegal and legitimate cargo, procedures and algorithms to uniform X-ray images of different cargo scanners, and an automated identification of potentially illegal cargo.

Aim of the presented approach is the early detection of defects (mainly material inhomogeneities like voids, delaminations, kissing bonds) occuring during the additive Laser Metal Deposition (LMD) process. Basis of the approach is the evaluation of the surface temperature gradient within the welding spot using a high speed thermographic sensor. Our contribution covers the following aspects: • Estimation of the expected defect contrast by means of a simulation study Second point • Experimental setup and performed experiments • Achieved results on different welding parameters and mock-up defects together with the associated image processing chain First experiments showed that a set of process parameters can be monitored through the temperature signature of the welding spot. Also, the available defects have been detected down to a diameter of 0.5 mm. The presented work has been carried out within the research project ‘ForNextGen’ funded by the Bavarian Research Foundation and is part of the work package 6 (Non destructive testing).

To measure the origins and dependencies of image lag in indirect converting flat-panel detectors, different methods were implemented. According to ASTM E 2597-07, the detector will be irradiated for a defined period with a constant flux. Then shutting off the tube, one can determine the image lag by monitoring the detector signal. We developed a different method, using a triggered shutter, to enable exactly defined illumination of the detector. Integration times longer than 1 s allow an exposure only during the delay time of the detector. This way, comparable results for image lag for decreasing intensity can be obtained. To investigate the image lag for increasing intensity, the triggered shutter stays open. By opening the shutter for more than one frame, then closing, it is possible to observe the build-up and decay of the image lag in dependence on the illumination time. Using these methods image lag was investigated with respect to irradiation intensity, time, incident X-ray spectrum, gain capacity of the detector and lag homogeneity of the detector surface.

Recent developments of direct converting X-ray detectors with good efficiency in the lower (10 keV) to the higher (>200 keV) energy ranges will become more and more of interest for applied non-destructive testing purposes. In this publication, we present different tests for characterization and comparison of detectors used in low-energy and high-resolution radioscopic and computed tomography applications. The characterization and application tests were performed on the direct converting X-ray detector Ajat DIC 100TL (Oy AJAT Ltd.) which is based on CdTe with a CMOS readout and the indirect converting X-ray detector C9311DK (Hamamatsu) which is based on CsI with a CMOS readout. The results of different characterization criteria on one hand valid for all detector types and applications like basic spatial resolution (BSR), MTF, SNR and efficiency and on the other hand criteria especially for NDT in designated application fields are presented and compared for the two detectors.

The inspection of very large objects like sea freight containers with X-ray Computed Tomography (CT) is an emerging technology. A complete 3-D CT scan of a see-freight container takes several hours. Of course, this is too slow to apply it to a large number of containers. However, the benefits of a 3-D CT for sealed freight are obvious: detection of potential threats or illicit cargo without being confronted with legal complications or high time consumption and risks for the security personnel during a manual inspection. Recently distinct progress was made in the field of reconstruction of projections with only a relatively low number of angular positions. Instead of today’s 500 to 1000 rotational steps, as needed for conventional CT reconstruction techniques, this new class of algorithms provides the potential to reduce the number of projection angles approximately by a factor of 10. The main drawback of these advanced iterative methods is the high consumption for numerical processing. But as computational power is getting steadily cheaper, there will be practical applications of these complex algorithms in a foreseeable future. In this paper, we discuss the properties of iterative image reconstruction algorithms and show results of their application to CT of extremely large objects scanning a sea-freight container. A specific test specimen is used to quantitatively evaluate the image quality in terms of spatial and contrast resolution and depending on different number of projections.

X-ray computed tomography (CT) is an established tool for industrial non-destructive testing purposes. Yet conventional CT devices pose limitations regarding specimen dimensions and material thicknesses. Here we introduce a novel CT system capable of inspecting very large objects (VLO) like automobiles or sea freight containers in 3-D and discuss strategies for efficient scanning and reconstruction methods. The system utilizes a 9 MeV linear accelerator to achieve high penetration lengths in both dense and high-Z materials. The line detector array has an overall length of 4 meters. The presented system allows for reconstruction volumes of 3.2 meters in diameter and 5 meters in height. First we outline the general capabilities of high energy CT imaging and compare it with state of the art 450 kV X-ray systems. The imaging performance is shown based on experimental results. The second part addresses the problem of considerably higher scanning times when using line detectors compared to area detectors. Reducing the number of projections considerably causes image artifacts with standard reconstruction methods like filtered back projection (FBP). Alternative methods which can provide significantly better results are algebraic reconstruction techniques (ART). One of these is compressed sensing (CS) based ART which we discuss regarding its suitability in respect to FBP. We could prove the feasibility of inspecting VLOs like complete automobiles based on experimental data. CS allows for achieving sufficient image quality in terms of spatial and contrast resolution while reducing the number of projections significantly resulting in faster scanning times.

A study is shown which is performed to enhance an existing deterministic X ray simulation method for nondestructive testing applications by including the effect of pair production and annihilation. Therefore a Monte Carlo simulation tool was used to perform parameter studies. Several materials from polyvinyl chloride to lead and of different lengths were simulated with 109 monoenergetic photons per simulation run. These were used to quantify and evaluate the radial distribution of scattered photons for each length material and energy as a function of the scattering angle. The results indicate that the radiation originating from the electron positronannihilation and thus from the pair generation is one major contributor to the total deposited energy only for certain angular ranges whereas for other angles Compton is by far the leading scattering effect. Furthermore the results indicate that the electron positron annihilation radiation is negligible for most imaging tasks and thus unimportant for deterministic scattering simulations.

In the field of X-ray imaging flat-panel detectors which convert X-rays into electrical signals, are widely used. For different applications, detectors differ in several specific parameters that can be used for characterizing the detector. At the Development Center X-ray Technology EZRT we studied the question how well these characteristics can be determined by only knowing the layer composition of a detector. In order to determine the required parameters, the Monte-Carlo (MC) simulation program ROSI [J. Giersch et al., Nucl. Instr. and Meth. A 509 (2003) 151] was used while taking into account all primary and secondary particle interactions as well as the focal spot size of the X-ray tube. For the study, the Hamamatsu C9311DK [Technical Datasheet Hamamatsu C9311DK flat panel sensor, Hamamatsu Photonics, ( www.hamamatsu.com )], a scintillator-based detector, and the Ajat DIC 100TL [Technical description of Ajat DIC 100TL, Ajat Oy Ltd., ( www.ajat.fi )], a direct converting semiconductor detector, were used. The layer compositions of the two detectors were implemented into the MC simulation program. The following characteristics were measured [N. Uhlmann et al., Nucl. Instr. and Meth. A 591 (2008) 46] and compared to simulation results: The basic spatial resolution (BSR), the modulation transfer function (MTF), the contrast sensitivity (CS) and the specific material thickness range (SMTR). To take scattering of optical photons into account DETECT2000 [C. Moisan et al., DETECT2000—A Program for Modeling Optical Properties of Scintillators, Department of Electrical and Computer Engineering, Laval University, Quebec City, 2000], another Monte-Carlo simulation was used.

Besides the pixel size of the detector and the size of the focal spot the resolution of a computed tomography (CT) setup depends especially on the spatial stability of all components. In this publication we present the performance of our sub-μ-CT components and the limitations resulting from spatial instability of the system. We will show that it is possible to overcome these limitations and reach resolution in the range of 500 nm. The experimental setup is based on high-resolution imaging detectors, a multifocus X-ray tube and a high-precision manipulation system. Our research contains measurements of the effective focal spot size using a resolution test mask and of the long-term stability of the focal spot position due to thermal expansion of the focusing unit. Also the stability of the X-ray intensity that affects the quality of CT will be corrected by additional bright image correction during the measurement. Due to the measured instabilities correction of the original images is necessary to achieve highest resolution. Solutions and results will be presented.

The ECSIT project analyses how innovative inspection technologies can lead to an enhanced container security and how these technologies can be embedded into a holistic concept. It has the goal to analyze the possibility and feasibility for 100% scanning of all containers which are shipped to US ports and to develop a concept for integrating necessary infrastructure. A key element of the entire concept is the scanning technology itself. MeV X-ray technology using a linear accelerator as radiation source provides the feasibility to visualize the content of a container without opening it. If a 2-D radiography is ambiguous, a 3-D evaluation of the respective location could be conducted. MeV X-ray computed tomography (CT) is such a method to provide 3-D information of the content of a container. In the context of ECSIT, Fraunhofer EZRT has developed the concept of such a continuative high energy X-ray scanning stage and evaluated its application to sea freight containers. In this paper different approaches for measuring a 3-D tomographic volume data set of objects which are very heavy and thus difficult to move in arbitrary directions will be discussed. Three different geometrical principles for data acquisition were evaluated: laminography, limited angle CT, and a gantry CT. The volume data sets were reconstructed by using a standard filtered back projection and different algebraic reconstruction techniques (ART). Real 3-D volume data of large objects measured with the set-up described above are presented. As test objects a real container packed with various typical goods like furniture or consumer electronics as well as simulated threats like a bomb mock-up was used.

In medical applications and non-destructive testing, knowledge of emitted X-ray spectra of X-ray tubes can be of great importance, e.g. for quality control issues or material decomposition techniques. Conventional methods of measuring spectra with a photon counting detector positioned in the primary beam often show unsatisfactory results, especially when applying high flux in conjunction with high X-ray eYXB3-01138-A461nergies (above 100 keV). The two main problems arising are pulse pile up, i.e. the impossibility to differentiate between multiple photons in one readout interval, and the reduced detector efficiency at high X-ray energies because of limited sensor thickness. These effects lead to significant errors in the determination of X-ray tube spectra. To overcome these limitations we built a Compton spectrometer based on the Compton spectroscopy approach by Yaffe et al.

State of the art X-ray imaging sensors comprise a trade-off between the achievable efficiency and the spatial resolution. To overcome such limitations, the use of structured and scintillator filled aluminum oxide (AlOx) matrices has been investigated. We used Monte-Carlo (MC) X-ray simulations to determine the X-ray imaging quality of these AlOx matrices. Important factors which influence the behavior of the matrices are: filling factor (surface ratio between channels and 'closed' AlOx), channel diameter, aspect ratio, filling material etc. Therefore we modeled the porous AlOx matrix in several different ways with the MC X-ray simulation tool ROSI [1] and evaluated its properties to investigate the achievable performance at different X-ray spectra, with different filling materials (i.e. scintillators) and varying channel height and pixel readout. In this paper we focus on the quantum efficiency, the spatial resolution and image homogeneity.

X-ray techniques are commonly used in the fields of non-destructive testing (NDT) of industrial parts, material characterization, security and examination of various other specimens. The most used techniques for obtaining images are radioscopy for 2D and computed tomography (CT) for 3D imaging. Apart from these two imaging techniques, where X-ray radiation penetratesmatter, other methods like refraction or fluorescence analysis can also be used to obtain information about objects and materials. The vast diversity of possible specimen and examination tasks makes the development of universal X-ray devices impossible. It rather is necessary to develop and optimize X-ray machines for a specific task or at least for a limited range of tasks. The most important parameters that can be derived from object geometry and material composition are the X-ray energy or spectrum, the dimensions, the examination geometries and the size of the detector. The task itself demands a certain image quality which depends also on the X-ray spectrum, the examination geometry and furthermore on the size of the X-ray source’s focal spot and the resolution of the detector. Monte-Carlo (MC) simulations are a powerful tool to optimize an X-ray machine and its key components. The most important components are the radiation source, e.g. an X-ray tube and the detector. MC particle physics simulation codes like EGS (Nelson et al., 1985) or GEANT (Agostinelli et al., 2003) can describe all interactions of particles with matter in an X-ray environment verywell. Almost all effects can be derived from these particle physics processes. The MC codes are event based. Every single primary particle is generated and tracked along with all secondary particles until the energy of all particles drops below a certain threshold. The primaries are generated one after another, since no interactions between particles take place. When simulating X-ray sources, in most cases X-ray tubes, the primary particles are electrons. The electron beam is parameterized by the electrons’ kinetic energy and the intensity profile along the cross-section of the beam. When hitting the target, X-rays are generated by interaction of electrons with the medium. The relevant magnitudes for imaging are the X-ray energy spectrum and the effective optical focal spot size (Morneburg, 1995). The most used imaging systems in the field of NDT are flat panel detectors. There are two basic types of detectors: Direct converting semiconductor detectors and indirect converting scintillation detectors. The type of particle interactions in the respective sensor layer determines the detection efficiency and effective spatial resolution. Interaction of X-rays in direct converting detectors produces electron-hole-pairs in the semiconductor materials. The free charge carriers drift to electrodes,where the current can bemeasured.MC simulations can Monte Carlo Simulations in NDT

Dual-energy computed tomography (DECT) is an established method in the field of medical CT to obtain quantitative information on a material of interest instead of mean attenuation coefficients only. In the field of industrial X-ray imaging dual-energy techniques have been used to solve special problems on a case-by-case basis rather than as a standard tool. Our goal is to develop an easy-to-use dual-energy solution that can be handled by the average industrial operator without the need for a specialist. We are aiming at providing dual-energy CT as a measurement tool for those cases where qualitative images are not enough and one needs additional quantitative information (e.g. mass density ρ and atomic number Z) about the sample at hand. Our solution is based on an algorithm proposed by Heismann et al. (2003) [1] for application in medical CT . As input data this algorithm needs two CT data sets, one with low (LE) and one with high effective energy (HE). A first order linearization is applied to the raw data, and two volumes are reconstructed thereafter. The dual-energy analysis is done voxel by voxel, using a pre-calculated function F(Z) that implies the parameters of the low and high energy measurement (such as tube voltage, filtration and detector sensitivity). As a result, two volume data sets are obtained, one providing information about the mass density ρ in each voxel, the other providing the effective atomic number Z of the material therein. One main difference between medical and industrial CT is that the range of materials that can be contained in a sample is much wider and can cover the whole range of elements, from hydrogen to uranium. Heismann’s algorithm is limited to the range of elements Z=1–30, because for Z>30 the function F(Z) as given by Heismann is not a bijective function anymore. While this still seems very suitable for medical application, it is not enough to cover the complete range of industrial applications. We therefore investigated the possibilities of extending the afore mentioned approach to dual-energy imaging to a wider range of materials.

In this paper we describe the optimization of transmission X-ray targets by Monte-Carlo simulation for a laboratory X-ray microscopy setup. We identified two optimal target layer thicknesses (0.1 mu m and 0.7 mu m) for a high-resolution target and a high-flux target. Measurements show a decrease in focal spot size by one third or an increase in X-ray flux by a factor of three compared to those of a standard micro-focus target. Focal spot sizes down to 154 nm and 260 nm are achievable with the optimized targets. Simulation results for the X-ray flux match well to the experimental results, whereas the results for the focal spot sizes still show discrepancies attributed to the simplified simulation setup.

Scintillator based flat panel detectors are state of the art in the field of industrial X-ray imaging applications. Choosing the proper system and setup parameters for the vast range of different applications can be a time consuming task, especially when developing new detector systems. Since the system behaviour cannot always be foreseen easily, Monte-Carlo (MC) simulations are keys to gain further knowledge of system components and their behaviour for different imaging conditions. In this work we used two Monte-Carlo based models to examine an indirect converting flat panel detector, specifically the Hamamatsu C9312SK. We focused on the signal generation in the scintillation layer and its influence on the spatial resolution of the whole system. The models differ significantly in their level of complexity. The first model gives a global description of the detector based on different parameters characterizing the spatial resolution. With relatively small effort a simula tion model can be developed which equates the real detector regarding signal transfer. The second model allows a more detailed insight of the system. It is based on the well established cascade theory, i.e. describing the detector as a cascade of elemental gain and scattering stages, which represent the built in components and their signal transfer behaviour. In comparison to the first model the influence of single components especially the important light spread behaviour in the scintillator can be analysed in a more differentiated way. Although the implementation of the second model is more time consuming both models have in common that a relatively small amount of system manufacturer parameters are needed. The results of both models were in good agreement with the measured parameters of the real system.

Production metrology faces challenges connected to the production industry where consumers of products expect a standard of high quality at inexpensive costs. One approach for the next generation of production metrology devices aims at ensuring the quality of the process technologies in every single process step, therefore measuring in-process. One example of today's production metrology devices is the measurement of shafts in the production. Shafts are vital for every mechanical device that translates rotational energies and the tolerances based on diameter or roundness are in the range of microns. Those shaft measurement devices are either based on tactile measurements or on visible light which cannot be utilized as an in-process device. A novel idea is to use X-rays instead of tactile or visible light methods to be able to acquire robust measurement data despite of distorting debris like water, oil or dust. One focus is set on algorithms that allow robust measurements of diameter and roundness despite of distorting debris like water, oil or dust. The measurement uncertainty of the new method has been investigated and results will be introduced.

When integrating optic measurement systems into or next to the production line for part inspection and control of the production process requirements for m easurement devices like the measurement time and the measurement uncertainty have to be expanded by a requirement for the robustness of the measurement system. A novel optic measurement system will be presented which is designed for the robust measuremen t of roundness of shafts next to the production line which is not influenced by residues of the manufacturing process, e.g. cooling lubricant. The measurement system is based on projecting the shadow of a shaft onto a detector and measuring the cast edges to derive the roundness of the shaft. The main parts of the measuring system consist of a soft X-ray micro focus tube, a highly precise angle measurement system and a CCD-detector. In contrast to roundness measurement instruments which are based on visible light and a telecentric optical path, new algorithms to calibrate the soft X-ray measurement instrument are being developed because of the divergent ray distributio n of the soft X-rays. This paper will introduce the design and the main elements of the novel soft X-ray projection system as well as algorithms needed to conduc t the roundness measurements. An estimation of accuracy and precision for small diameter shafts is presented as well as possibilities to achieve the invariance up to residues of the manufacturing process. Keywords: non-contact measurement, soft X-rays, production metrology, form measurement