What X-Scan Will Do
Our immediate goal in this project is the development of a truck-portable x-ray source that will emit 100 J of X-ray energy at average photon energies above 100 keV. We anticipate pulse durations of the order of 4-8 ns and source size approximately 20 by 80 microns or smaller. Pulse repetition rates will be basically limited by the power source but will be in excess of one per second.
We have already demonstrated in laboratory experiments the achievement of our goal for an x-ray source. We generated over 100 J of x-ray energy with an average photon energy above 1 Mev. This radiation was detected through a 6” thick shield of copper and steel and generated a signal-to-noise ratio of over 1,000. The pulse duration was 4 ns. While the source size was somewhat larger than our goal, with 200 microns radius, we anticipate source size will be decreased in very near-term experiments. The experimental device used to generate this weighs 3 tons including all equipment and so could be modified to fit in many trucks. We consider the research on this source to be complete, although engineering development into a product is still required.
This source will be integrated into an inspection device that will be able to scan roads, bridges and buildings with source and detector both located within the truck (or on a gantry). The X-ray source will repeatedly pulse as the truck moves, emitting sheets of X-rays collimated by lead shields.
X-rays scattered from the structure will then be imaged using a pinhole or other imaging method. This instrument will be capable of scans with resolution of 2 mm up to 32 cm (1 foot) into concrete and up to 8 cm (3.2 inches) into steel. This is sufficiently capable for one-sided scanning of roadways, bridge structures, reinforced concrete girders and other large infrastructure components. The outer 10-30 cm of structural elements is the portion that is most important to inspect since corrosion and other fault processes occur from the outside inward.
We also intend to integrate the same X-ray source into other types of instruments. One major area of application is high resolution inspection of thick manufactured parts. The DPF X-ray source used as a direct, rather than scattering, source will achieve 20 micron resolution in steel parts as much as 16 cm thick. Such high resolution reveals micro-cracks that are important for high stress parts such as pressure vessels.
Another major application area is as an economical source of high intensity X-rays for high speed laboratory diagnostics. While laser-based X-ray sources exist with pulse durations as short as femtoseconds, existing sources have emission energies in the range of nano J. In contrast X- Scan pulses will produce 30-100 J. The combination of high pulse energy with high photon energy and ns-pulse duration makes possible studies of fast processes occurring in dense matter, such as explosion dynamics.
In addition, the high flux will make possible high space and time resolution of fast plasma phenomenon. At the low end of the X-ray energy range, a DPF X-ray source at a distance of one meter will provide 10,000 photons per square micron. With a source size of 20 microns along the axis, resolution of a few tens of microns of fast phenomenon will be achievable.