Gongyin Chen

Radioscopic inspection of cargo containers with megavoltage energy barriers

To perform the inspection of cargo containers the radioscopic screening is performed by switching between 6 and 9 MeV of boundary energies as rapidly as 200 times per second and measuring the penetration levels in the contents of cargo. This technology facilitates the material identification via the analyses of the ratios of signals obtained at nominal and dual energies, which are 6 and 9 MeV, respectively. The techniques are developed for (a) visualizing the contents to produce an image suitable for fast inspection by a human operator, and for (b) prompting the custom personnel about the location of suspicious objects. Specifically, nuclear materials are of interest. The experiments have been conducted with Linatron K9 device designed by Varian Security and Inspection Products [1]. The capabilities are demonstrated for detection of objects of interests for the steel shields of 10 inches of thickness.

X‐Ray Cargo Inspection: Status and Trends

Over the past several years, x‐ray cargo inspection has experienced tremendous growth. There are several hundred systems in use world wide and a few new units are installed every week. Fielded systems are mostly located in north and West Africa, Middle East, Europe (especially Russia), East Asia, and South America. The majority of systems are powered by Varian M3, M6 or M9 Linac x‐ray sources. The spatial resolution of these systems is typically 3–5 mm, penetration ranges from around 200 mm to 450 mm of steel and contrast sensitivity is typically 1–4%. Inspection throughput ranges from about 20 trucks per hour to 200 trucks per hour. Currently the systems are primarily used to fight import tax evasion and smuggling of controlled substances. There are a few clear trends: Imaging performance has been steadily improving; a variety of systems have been developed to fit different needs; also, there is a strong effort in material discrimination, or even identification and automatic detection. The last, but not ...

Advantages and Challenges of Radioscopic Detection of Nuclear Materials in Cargo Containers with Two Megavoltage Energy Barriers

Abstract Megavoltage X-ray technology is utilized to detect fissile materials that can be smuggled by terrorists among commercial goods in cargo containers. Material discrimination with dual energy barriers is based on a ratio of penetration levels at respective energies. However, for a broad bremsstrahlung spectrum, the approach is not reliable because of its sensitivity to mass thickness. Furthermore, cargo containers usually have combinations of materials in a stack that further complicates material identification. It is imperative to study the capability of dual mega-electron-volt energy radioscopy to detect materials of interest for its practical application at customs. The time to perform this inspection automatically and the need to manually open the container for examination are to be minimized for the smooth transport of goods through the national border. In this work, Linatron K9, developed and manufactured by Varian Inc., Inspection and Security Products, is used for experimentation. By switching 6- and 9-MeV beams, an interlaced penetration response is obtained. The automated detection of materials of high atomic numbers in the stack of materials is performed by proposed adaptive thresholding algorithm. The evaluation of the system based on a worst case scenario shows that the system meets requirements defined in the congressional report in terms of true and false positive identification rates, smallest object resolution, and the processing time.