Brighter Screens for Nondestructive Digital X-ray Radiography

Technical Report · Mon Sep 15 00:00:00 EDT 2003

DOI:https://doi.org/10.2172/1017410· OSTI ID:1017410

Bell, Z W; Carpenter, D A

Fine resolution, bright X-ray screens are needed for digital radiography and material characterization at the Y-12 National Security Complex (Y-12). Current technology is simply not adequate for transferring high-energy X-ray images to visible light for demanding digital applications. Low energy radiography and especially emerging tomographic technologies are severely hampered for Y-12 nondestructive evaluation (NDE) applications by dim screens with poor resolution. Also, the development of more advanced materials characterization techniques, such as electron backscatter diffraction (EBSD), is driven by a design agency desire for tighter specifications and more uniform materials. Brighter screens would allow us to probe materials on a finer scale, leading to a better understanding of material behavior. A number of X-ray screen materials were studied that would be suitable for direct replacement in existing digital imaging systems. Spectroscopic evaluations were first made for a several candidates and indicated that lutetium orthosilicate (LSO) would be a promising candidate for MeV images. A relative comparison of brightness at various energies was then completed which showed that cesium iodide (CsI) could increase brightness by over an order of magnitude. Since image quality is also important for better screens, the resolving capabilities of candidate materials were measured. Resolution measurements were completed at X-ray peak energies up to 420KeV with magnified optical imaging systems, and indicated that LSO and Industrial Quality Incorporated glass (IQI) exhibited higher resolution than the CsI screen. The results give a choice of materials that can be tailored to the particular test under consideration. If high-speed images are necessary and some resolution can be sacrificed, the CsI screen will be a good choice. The screen can be replaced by an IQI or LSO unit if higher resolution is needed later, for instance to focus in on a region of interest. A number of significant findings were obtained from this study. Most important of the findings was that materials are commercially available that are much brighter than screens currently in use. This finding meets the original objective of the project. Two objectives of the study; however, were not met. We hoped to evaluate a 'quantum dot' (nanometer-sized particles of semiconductor material) wavelength conversion screen, but the manufacturer ceased production of the screen shortly before the project was started. The dot screen could be efficient in converting ultraviolet light to visible light which would have proved important for utilizing a Cherenkov screen. Since this was a very new, cutting-edge technology, an alternative supplier was not found during the study. Also, high-energy testing of a Cherenkov light screen was not performed due to difficulties in obtaining appropriate approvals for locating test equipment in the high-energy X-ray vault at Y-12. The test is still important, and is being pursued through follow-on funding sources. Although many film shots will be eliminated by the availability of high quality digital images, the largest potential gains result from the availability of clearer images that show fine detail in the parts under analysis. Digital radiographic data also offers the possibility of easily sharing data with other sites. This could prove invaluable when critical material, placement, assembly, or quality issues are pressing. Also, increased throughput in the NDE facility allows statistically significant numbers of units to be analyzed. Digital technologies may in fact be needed just to meet minimum requirements of future demands. Increased brightness screens allow for such innovations as 3-D tomographic images to be acquired in a reasonable time. Much of the skill required to interpret 'flattened' X-ray images is not needed to maneuver around the reconstructed tomogram. This study showed that several commercially available materials are much brighter than screens currently in use. The study also showed that materials other than the brightest may be preferred for the best resolution. Since the X-ray conversion screen can be designed for easy exchange, a combination of materials will ultimately be the best approach for the broad range of radiography analysis performed at Y-12.

• Research Organization: Oak Ridge Y-12 Plant (Y-12), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Defense Programs (DP)
• DOE Contract Number: DE-AC05-00OR22800
• OSTI ID: 1017410
• Report Number(s): Y/DW-1922; TRN: US201113%%714
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
BRIGHTNESS
CESIUM IODIDES
DESIGN
DIFFRACTION
ELECTRONS
EVALUATION
GLASS
LUTETIUM
MANUFACTURERS
NATIONAL SECURITY
PRESSING
PROBES
PRODUCTION
RESOLUTION
SCREENS
SEMICONDUCTOR MATERIALS
SPECIFICATIONS
TESTING
WAVELENGTHS
X-RAY RADIOGRAPHY