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Seeing your way with X-ray screening.

X-RAY SECURITY SCREENING SYStems were initially developed to detect metal weapons concealed by hijackers, who were the primary security threat 20 years ago at airports.

Today the use of X-ray screening systems has expanded beyond airports to include correctional facilities, courthouses, nuclear power plants, government facilities, military bases, and corporate offices to name just a few. Equipment also has been leased or rented by schools and for events such as the Olympics, professional sports, and political conventions.

Most recently, communications centers and high-profile organizations at risk from terrorist activities or other threats are using X-ray security screening systems. The use of X-ray security screening systems has become truly universal.

The equipment was first deployed on a large scale in the early 1970s in airports. For detecting weapons, the best conventional black-and-white imaging systems are equipped with two linear X-ray detector arrays configured in an L shape or a folded array so the collimated, fan-shaped X-ray beam covers all parts of the tunnel.

Consequently, there is no baggage or package cutoff during the scanning process. With these systems, metallic weapons-such as guns and knives-are easily seen because they are dense and have distinctive shapes.

In 1980, the first digital system, which used silicon diode array sensors, was introduced. The system dramatically improved image quality and was safe for photographic film.

As the need for detecting explosives became paramount during the 1980s, the dual energy system was developed. The objective of the system was to make explosives more identifiable.

The dual energy system classifies materials as organic or inorganic, depending on atomic number. Materials with atomic numbers below 10 are classified as organic and are displayed on the monitor in orange-brown shades. The items included in this group are explosives and narcotics. Materials with atomic numbers above 10 are inorganic and are displayed on the monitor in blue shades. They weapons.

Dense objects that cannot be penetrated by low-energy Xrays are ambiguous and show up on the monitor as green. When this happens, well-trained operators will call a supervisor or manually search the contents of the bag themselves.

RECENT TECHNICAL developments have led to dramatic improvements in earlier systems. Enhancements fall into the following categories: video enhancement, edge enhancement, improved X-ray penetration, improved resolution, and inorganic stripping.

Video enhancement provides a crisper color image. Edge enhancement provides improved line definition and a sharper color image.

Improved X-ray penetration through at least 17 mm of steel plate reduces the number of green, too-dense-to-penetrate areas. Improved resolution in both black-and-white images and dual energy color images is now available for users in X-ray screening technology.

In black-and-white systems, 30 AWG (American Wire Gauge) solid copper wire should be visible to users through 10 levels of an ASTM (American Society for Testing and Materials) step wedge.

In dual energy systems, at least 24 AWG solid copper wire should be visible through all 10 levels of an ASTM step wedge, and at least 30 AWG solid copper wire should be visible through five levels of an ASTM step wedge.

Inorganic stripping, available on some dual energy systems, allows the operator-at the push of a button to strip away extraneous, inorganic information to highlight potential explosive threat areas.

Exhibit 1 represents a dual energy system standard image of a laptop computer with a hidden potential explosive threat.

Exhibit 2 represents the enhanced inorganic stripping image of the same laptop computer, highlighting potentially explosive material as the dark orange square.

The benefit of advanced X-ray systems and enhancements is to provide properly trained operators with superior, proven tools to identify potential explosive threats in complex, confused environments, such as electronic devices and luggage.

Some manufacturers offer a system called backscatter, which measures the mass distribution of the material along the line of sight. As a result, an organic mass inside the wall of a screened object will show much more prominently than the same amount on the center of the bag.

One way to alleviate this problem is to provide a second generator on the other side of the object. This, however, results in a more complex and expensive system as compared to the other option of dual energy that is available to users.

Dual energy, on the other hand, uses the transmitted X-ray image, which penetrates the object and only requires a single generator. It is more simple, reliable, and less expensive.

Another advantage of the dual energy system is that the primary image information is displayed on one color monitor, while the backscatter system requires the operator to scan two black-and-white monitors, a practice that can be tiring and confusing.

While both backscatter and dual energy systems help operators detect potential explosive threat areas, dual energy is harder to defeat and more suitable for airports and other high-traffic applications where reliability and maintainability are critical.

SECURITY MANAGERS THINKING ABOUT buying an X-ray screening system should consider several factors, including a facility's assets, risks, configuration, space limitations, and throughput at peak hours.

In addition, applicable government regulations must be met. Of course, the budget and the implementation schedule are an integral part of the planning process.

Radiation leakage must not exceed the maximum leakage of 0.5mR/hr (milliroentgens per hour) permitted by the Food and Drug Administration's Standard 21-CFR 1020.40.

The X-ray system should be safe for photographic film even at speed ratings of ISO 1600 as well as for magnetic data, such as those stored in laptop computers or diskettes.

Compact X-ray screening systems are available for examining small packages and briefcases. A unit with short conveyors, like the one shown in Exhibit 3, is ideal for screening in small places, such as courthouses.

The latest systems typically come equipped with membrane switch control panels. (See Exhibit 4.)

The membrane control panel has proven to be reliable in other products, such as automated teller machines, gasoline credit card systems, and fast-food cash registers. The panel also is immune to moisture damage and physical abuse.

In applications where hand-held packages and briefcases must be screened in medium to heavy throughputs, the standard airport system is recommended. Recent applications for this system include passenger cruise lines.

When large suitcases and checked baggage must be screened, systems with tunnel sizes that are capable of accommodating big items are available. Extended conveyors and baggage slides also are available.

Airlines, port authorities, and military and civilian government agencies are using mobile X-ray systems in van or trailer configurations. (See Exhibit 5.) These systems are designed with auxiliary power units so they can be used at remote locations.

In choosing a manufacturer, the security manager needs to consider the warranty for parts and service and ask the following questions:

* Do you offer the convenience of paying by credit card?

* Do employees or contract agents perform the work?

* How quickly will you respond?

* Do you offer self diagnostics or remote diagnostics?

* Do you offer modular construction, which facilitates fast service?

* Are all electronic components solid-state except for the X-ray tube and monitor tube?

One company offers a false-image projection feature whereby selected threat objects are digitally recorded and, at the supervisor's discretion during training, appear at random in the scanned images. (See Exhibit 6.)

An operator must be alert and press the control panel's threat subject button to make the false threat object disappear. (See Exhibit 7.) An operator's actions can be recorded and integrated into an ongoing training program for later use.

Several companies offer formal operator training. Others provide professionally trained X-ray scanning operators under contract to the facility operator for immediate technical expertise.

A variety of X-ray screening equipment is available. Whatever a facility's applications, reliable X-ray screening systems can be built or furnished to meet its requirements for detecting weapons and explosives.
COPYRIGHT 1992 American Society for Industrial Security
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Author:Moulpied, David S. de; Schwarzmann, Stephen T.
Publication:Security Management
Date:Mar 1, 1992
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