AIC's 44th Annual Meeting

With over 1,200 cultural institutions owning and operating portable X-ray fluorescence (XRF) analyzers, these instruments have become familiar tools for elemental analysis of collection objects. The X-ray source in these instruments can be repurposed for use in X-ray radiography. Successful trials demonstrate this imaging application and suggest the potential for its use on a variety of objects. This radiography method enables portable, small-scale imaging capability without traditional X-ray equipment or beta plates. Tests were carried out using a Bruker Tracer III-V handheld XRF analyzer. This instrument uses an X-ray tube and is capable of producing a voltage range of 0-45kV and an amperage range of 0-60μA. The XRF unit was mounted on a tripod and operated through a computer, allowing the energy levels to be adjusted and the operator to work at a distance from the X-ray beam. The X-ray beam is emitted at approximately 45° relative to the perpendicular of the face of the unit. The instrument was positioned to compensate for this angle, ensuring the object and film were within the beam. An intensifying screen, removed from a film cassette for medical radiography, was used to aid in placement. The intensifying screen is coated with phosphors that convert X-ray energy into visible light, permitting the beam spot size, shape, and location to be viewed in the dark. As with traditional X-ray radiography, the spot-size increases as the distance between X-ray source and target increases, also necessitating a longer exposure. The current in the portable unit is 1,000 times less than in traditional X-ray radiography equipment, and therefore longer exposures are required. Fugi Super HR-T and Kodak BioMax MR films were used and developed in an automatic processor. Recommended safety protocols were followed. X-ray images were successfully produced of paper to record the watermark and wood to evaluate the length of an embedded metal screw. At the following exposures, a working distance of 15 inches resulted in a usable image size of approximately 6 inches in diameter. A sheet of handmade paper with a thickness of 0.008 inches was exposed for 30 minutes at 15kV and 45μA. The resulting image of the watermark and laid lines had less contrast than a beta radiograph of the same sheet, but took less than half the time to produce. A ¾-inch thick block of balsa wood was exposed for 20 minutes at 45kV and 43μA. The wood grain was clearly visible in the X-ray image, as was the presence of an embedded metal screw. More information about the metal screw might be obtained with different operating parameters, but the capacity of the portable instrument may limit the ability to penetrate and record dense materials. Although not suited to all circumstances, this radiography method offers utility, flexibility, and relative ease. A watermark can be recorded without a beta plate; the presence of a pin, crack, join, etc. can be determined without a traditional X-ray imaging facility. The widespread availability of portable XRF units makes such exploratory radiography accessible for a variety of applications.