
X-ray diffraction sensor module for airport security
CEA-Leti in France has developed a detection module for small-angle X-ray diffraction that is being used in a new design of airport baggage scanner.
The SDX 10060 XDi developed by Smiths Detection uses the X-ray diffraction developed by CEA-Leti rather than a transmission system.
At an airport, every piece of luggage, whether carry-on or check-in, must thoroughly be screened for weapons, explosives and narcotics.
The information provided by such a scanner is not always sufficient to accurately determine the nature of an object. For example, two different liquids with similar densities are likely to be displayed in the same way. When in doubt, airport security operators have to open the baggage and carry out a manual check, which is time-consuming and increases the risk of human error. These limitations can be overcome by analyzing X-ray diffraction signals at small angles measured by spectrometric detectors.
“This involves emitting photons via X-ray sources and using detectors to observe those that have made it through the object,” says Loïck Verger, Partnership Manager for X-ray and Gamma-Ray Imaging Systems at CEA-Leti. “Subsequent data processing then allows the recreation of a 2D or 3D contrast image of the object.”
“Among the photons emitted, some will ‘bounce’ off objects and have their trajectory deviated by a small angle without losing energy,” he said. “This information is characteristic of the material they pass through. Consequently, by correctly detecting these photons and accurately measuring their energy at given angles, it is possible to deduce the molecular signature that characterizes their interatomic distances.”
This information is more precise than that provided by transmission imaging and makes it possible to rapidly examine a piece of luggage without having to immobilize and open it.
“The detection module we simulated, integrated, tested and transferred to Smiths Detection consists of a CdZnTe semiconductor detector operating at room temperature, an ASIC used to extract very weak signals originally developed by CEA-Irfu for astrophysics, and a specialized signal processing solution,” describes Loïck Verger.
Each scanner is equipped with several detection modules as well as information processing algorithms and X-ray generators. Designed to pass the most stringent certifications for the detection of illicit substances, this equipment is now on the market.
The detector technology was developed by CEA and is protected by fifteen patents. It was transferred to Smiths Detection as part of a licensing agreement.
“This detector technology enabled us to realize a new scanner geometry allowing for faster scanning speeds at significantly lower system and maintenance costs than would have been possible with cryogenic-detectors,” says Jens-Peter Schlomka, Head of R&D for diffraction at Smiths Detection.
The X-ray diffraction system can also be used in the medical sector as well as for molecular imaging, in particular for theranostics – a new medical approach aimed at the simultaneous development of diagnostic and therapeutic applications in nuclear medicine.
“While these applications have nothing in common, they are based on the same principle: a semiconductor detector combined with an ASIC integrated circuit and signal processing capabilities,” says Verger.
Leti has also worked with Thales on a portable full body X-ray system as well as 3D x-ray imaging for security and medical applications.
