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An overview of the radiographic capabilities with emphasis on electronic image detection and processing at the Los Alamos National Laboratory is presented. Fixed facilities and portable x-ray sources and imaging systems make up the Los Alamos capability. Examples of imaging with large area amorphous silicon imaging panels, a portable computed tomography system, high speed x-ray imaging applications and equipment, and small area, high resolution imagers are given. Radiographic simulation and reverse engineering from radiographic images to computer aided design files and solid models is also presented.

The use of the EG&G-Heimann RTM 128 [1] or dpiX FS20 [2] amorphous silicon (a-Si) detector array for thermal neutron radiography/computed tomography has proven to be a quick and efficient means of producing high quality digital radiographic images. The resolution, although not as good as film, is about 750 μm with the RTM and 127 μm with the dpiX array with a dynamic range in excess of 2800. In many respects using an amorphous silicon detector is an improvement over other techniques such as imaging with a CCD camera, using a storage phosphor plate or film radiography. Unlike a CCD camera, which is highly susceptible to radiation damage, a-Si detectors can be placed in the beam directly behind the object under examination and do not require any special optics or turning mirrors. The amorphous silicon detector also allows enough data to be acquired to construct a digital image in just a few seconds (minimum gate time 40 ms) whereas film or storage plate exposures can take many minutes and need to be digitized with a scanner. The flat panel can, therefore, acquire a complete 3D computed tomography data set in just a few tens of minutes. While a-Si detectors have been proposed for use in imaging neutron beams [3], this is the first reported implementation of such a detector for neutron imaging [4].

We developed a straightforward way to transform x-ray computed tomography (CT) data into an engineering model in a Computer Aided Engineering (CAE) software package. Engineers use such reverse engineering techniques to compare the component “as-is” to the component “as-designed.” Reverse Engineering is also useful when the documentation for components is lost or the component has been shaped by hand for design (as in automotive bodies) or to fit into a location.

In support of stockpile stewardship and other important nondestructive test (NDT) applications, we seek improved methods for rapid evaluation of materials to detect degradation, warping, and shrinkage. Typically, such tests involve manual measurements of dimensions on radiographs. We seek to speed the process and reduce the costs of performing NDT by analyzing radiographic data using a least-square fitting technique for rapid evaluation of industrial parts. In 1985, Whitman, Hanson, and Mueller have demonstrated a least-square fitting technique that very accurately locates the edges of cylindrically symmetrical objects in radiographs. [1] To test the feasibility of applying this technique to a large number of parts, we examine whether an automated least squares algorithm can be routinely used for measuring the dimensions and attenuations of materials in two nested cylinders. The proposed technique involves making digital radiographs of the cylinders and analyzing the images. In our preliminary study, however, we use computer simulations of radiographs.

In support of stockpile stewardship and other important missions, Los Alamos is continually looking for fast and effective ways of inspecting and evaluating industrial parts. Thus, Los Alamos is continually striving to improve our radiography and computed tomography (CT) capabilities. Cormack [1] and Hounsfield [2] received the Nobel Prize in 1979 for their pioneering work in computed tomography that led to the development of medical scanners. Copley et al. [3] provides a good history of the development of industrial CT systems. The early systems collect data via a single detector or linear detector array. While CT offers greatly increased spatial resolutions over radiography, CT inspections with a linear array are slow and costly. To improve the viability of CT for NDT applications, Feldkamp, Davis, and Kress [4] reported a cone beam reconstruction technique that speeds up the CT process by using image data rather than data collected by a linear array. Because it potentially offers processing speeds up to 10 times faster than CT systems that use a linear array, we are building a cone beam CT for use with our 20 MV x-ray source and Los Alamos Neutron Science Center (LANSCE) neutron sources. Our software, called CoBRA, is a portable cone beam reconstruction code for CT applications that efficiently and rapidly reconstructs large data sets. CoBRA applications include both x-ray and neutron inspections using x-ray phosphor screens coupled to either a CCD camera or flat-panel amorphous silicon arrays. Photographs of two amorphous silicon arrays (128 × 128 and 1600 × 200) are shown in Figure 1.

As a result of an arms reduction treaty between the United States and the Russian Federation, both countries will each be storing over 40,000 containers of plutonium. To help detect any deterioration of the containers and prevent leakage, we are designing a digital radiography and computed tomography system capable of handling this volume reliably, efficiently, and at a lower cost.

A gauge measures areal density variations as small as 0.1% in low density plastic foams and other materials. It has a spatial resolution of 0.5 mm. This system is safe, portable, easy to use, and is readily automated. The 6 keV x-ray flux from a /sup 55/Fe source is collimated to a 0.5 mm diameter beam and attenuated by the sample. Transmitted x-rays are detected with a proportional gas detector and counted with a scaler-timer. After measuring the x-ray attenuation in two areas of the sample, the areal density variation is calculated using an

We present measurements of the performance of a Pockels readout optical modulator (PROM) x‐ray imaging detector using a 30‐kV constant potential bremsstrahlung source. A nickel step wedge was used to measure the spatial resolution and noise of the PROM image. PROMs are unique high‐efficiency x‐ray detectors that image with good spatial resolution over a wide range of x‐ray energy. The PROM is constructed from an optically transparent, active crystal that is sensitive to x‐ray dose. This unique construction allows the use of a thick crystal to increase efficiency for x‐ray detection while avoiding the spatial resolution degradation that usually accompanies thick detectors.

Low-light-level cameras used with phosphors detect very small contrast differences and very small features in x-ray images. I used (1) a silicon-intensifier-tube television camera coupled by a fiber optic to a phosphor screen and (2) an integrating chargecoupled device camera focused on a phosphor to detect in a digital image a 0.27% contrast difference and 2-μm-diam wires.

A new contact microradiographic system for analyzing laser fusion targets with two-dimensional modeling and image-analysis techniques is described. This system, which uses a monochromatic x-ray source and Kodak High-Resolution Plate emulsion, is sensitive to spherical wall-thickness variations (eccentricities) as small as +- 200 A in hollow shells with a mean wall thickness of 1 ..mu..m. Measurements of wall thickness and of local and spherical wall-thickness variations by radiographic techniques, using two-dimensional video, digital image analysis, and optical interferometry, are compared. In addition, three digitizing systems are compared for converting the radiographic data to digital form.

We have developed x-ray radiography to measure thickness variations of coatings on laser fusion targets. Our technique is based on measuring the variation in x-ray transmission through the targets. The simplest targets are hollow glass microshells* or microballoons** 100 to 500 μm in diameter (Fig. 1), that have several layers of metals or plastics, 1 to 100 ym thick (Fig. 2). Our goal is to examine these opaque coatings for thickness variations as small as 1% or 0.1%, depending on the type of defect. Using contact radiography we have obtained the desired sensitivity for concentric and elliptical defects of 1%. This percentage corresponds to thickness variations as small as 100 A in a 1-μm-thick coating. For warts and dimples, the desired sensitivity is a function of the area of the defect, and we are developing a system to detect 0.1% thickness variations that cover an area 10 μm by 10 μm.

Digital subtraction radiography serves angiography [1] and other medical applications successfully to extract minute x-ray signals from noisy backgrounds. Verhoeven [2] demonstrated that detecting surprisingly small changes in x-ray absorption makes this technique useful for industrial applications as well. I detect very small areal density differences and also wires as small as 2 µm in diameter although the spatial resolution of my x-ray apparatus is 1 mm.

A new contact microradiographic system for analyzing laser fusion targets with 2-D modeling and image analysis techniques is described. This system, which uses a monochromatic x-ray source and Kodak highresolution plate emulsion, is sensitive to spherical wall thickness variations (eccentricities) as small as +/-200 A in hollow shells with a mean wall thickness of 1 microm. Measurements of wall thickness and of local and spherical wall thickness variations by radiographic techniques, using 2-D video, digital image analysis, and optical interferometry, are compared.

The off-axis forward-scattered radiation from a low energy He-Ne laser, scattered by high density hydrosols, is studied experimentally and theoretically. The validity range of theoretical calculations is determined using four measurements with two optical depths and two detector fields of view. For narrow field of view detectors, experimental and theoretical agreement is good close to the beam axis and decreases with transverse distance; agreement is good at greater distances from the beam axis using an open detector. The small-angle approximation adequately describes multiple scattering close to the beam; calculations are significantly improved by combining the small-angle approximation with diffusion theory.