Recently, the Washington, D.C., police force field-tested a mobile radiation detection system, which proved that the system could quickly identify, locate and interdict threat radiation sources. These results led one official to say that the technology urgently was needed throughout the country.
Why the urgency? The radiation threats that the system is designed to detect and interdict are things like “dirty bombs,” which can be used by terrorists to target American cities, cherished landmarks, sporting events or wherever large crowds gather. The mobile system from Thermo Fisher Scientific used in the test instantly and automatically could identify a radiation threat even in very crowded, fast-moving conditions when a split-second response would be needed to prevent a disaster.
What follows is a description of how a mobile radiation system works and why this solution is becoming a necessity for police, first responders and other critical homeland security personnel around the United States.
DESIGNED FOR THE “TERRORIST AGE”
Detecting and monitoring hazardous materials in defined locations, like the workplace or a landfill, has been a standard practice for health and safety personnel. But in an era when the security of the entire country is at stake, the ability to detect hazardous material, especially radiation sources, has expanded to whole cities, sea ports, large sporting events and similar venues, making the need to quickly and effectively cover these areas very challenging.
A new generation of mobile radiation detection systems is being developed and deployed not only to overcome some of the weaknesses in more traditional radiation monitoring (i.e., the difficulty in quickly detecting a large area with hand-held or stationary devices), but also to detect radiation in a myriad of moving targets such as in trucks or being carried by people. The latter ability requires the capabilities of a mobile detection system.
Mobile radiation detection systems, however, put increased pressure on radiation detection principles that typically are not found in hand-held instruments. Detecting radiation from a moving vehicle introduces new hurdles to overcome: rapidly changing backgrounds, false alarms, detection accuracy, power constraints and ease of use. Mobile operators also are challenged to run systems that, in the past, were the domain of the scientist or an experienced radiation detection specialist.
The simple fact is that background radiation is present everywhere in natural form. It can be found in camera lenses, granite, brick, marble, clay and even in the human body itself.
Determining and maintaining a stable natural background benchmark (to distinguish “natural” from “threat” sources), therefore, is one of the key requirements to any good mobile radiation detection capability.
With mobile detection, one of the biggest challenges in getting a stable background reference point is the vehicle speed. Unlike portable instruments hand-carried by someone walking, a vehicle moving at a speed of 30 mph can travel a distance of 44 feet per second; which means in 5 seconds, a mobile unit could have passed 20 cars, half a city block and possibly 40 people. On any street in Washington, D.C., or New York City, this would result in the background rapidly changing, causing the detection system to be unstable and problematic in performing accurate and efficient radiation detection.
With such great change in background in a short period of time, traditional algorithms based on detector counts can't adequately manage a low false alarm rate. To avoid false alarms, engineers and scientists have developed new logical algorithms that not only look at the types of radiation and their interaction, but also speed, temperature, physical location and more.
Accuracy is the single most important requirement of any mobile radiation detection system and monitoring platform. To improve detection accuracy, engineers employ everything at their disposal in today's technology catalog: small high-speed processors, low-current stable power supplies, finely-tuned detector material, exotic detector shielding and special software/firmware. Significant breakthroughs, based on these advancements, include more effective detector sampling rates and algorithms.
Sampling rate is critical in a high-speed mobile radiation detection system. Using high-speed electronic processors, a new sampling rate of 1/10th of a second is achievable.
Increasing the sampling rate of a mobile detection system improves the accuracy of pinpointing a location and time of detection. Increased sampling rates means there are fewer counts in the multiple count channels being analyzed during a count period (1/10th of a second). This, in turn, lowers the number of background counts, making it easier to see smaller changes in background-to-foreground counts — all resulting in more sensitive and accurate measurements.
The new, more effective algorithms, based on Sandia National Laboratories research, not only have made a significant difference in the ability to detect sources more accurately, but also to detect radiation sources that may be shielded or masked by material such as concrete, steel or lead.
The algorithms mathematically take a picture of the detector results, and compare it to known databases of mathematical images that previously have been tested and verified in a laboratory setting. These templates are produced by professional physicists who have made it their job to perform accurate identification of radiation sources, no matter what the environment. As more mobile radiation systems are deployed, the ability to test against real environments will produce measurements for the physicist to use as new input into the counting system, making the systems even smarter and more accurate.
The mechanical installation and placement of the radiation detector equipment also is very important in the design of mobile detection systems. Just as a camera has a specific focal area of view of its subject, radiation detectors need a similar capability when searching for small amounts of radiation. Radiation detectors must be placed and positioned so the most sensitive area of the detector window is pointed in the right direction.
For sensitive radiation detection systems, clean power to drive the system is essential. Also, minimizing the amount of power needed for the system reduces the amount of permanently installed power equipment required. By utilizing lower power options, operators are not limited to specific vehicles with specialized power installations. Operators can move the radiation detection system between vehicles for continued availability of the system during, for example, vehicle maintenance and repairs. Lower power also stabilizes heating and potential temperature changes inside the vehicle environment that could cause additional detector accuracy issues due to detector drift.
EASE OF USE
Probably one of the most overlooked issues surrounding mobile radiation detection systems is ease of use. Mobile radiation detection systems challenge designers to develop user interfaces that would be as simple to use as a one-button television remote.
Mobile radiation detection systems can have as many as 100 channels of significant data that are required for the system to operate. For any operator, this amount of data is impossible to review when one is traveling at 30 mph, and the system is updating at speeds 1/10th of a second. Compressing 100 channels of data and providing analytical software to render a simple radiation level code (green for “normal,” yellow for “suspect” and red for “threat”) has, therefore, been a major accomplishment.
Simple user interfaces also impact operator training. As mobile radiation systems become much simpler to operate, it is possible to have an operator trained and operating the system within 30 minutes. With simple, intuitive interfaces, it no longer is necessary for the operator to spend hours in classroom training on something he or she may only use once a month.
Mobile radiation detection systems have enabled first responders, police and homeland security personnel to achieve sophisticated, accurate detection using a technology that until recently was only found in laboratories, nuclear centers or health physics operations. These new mobile radiation detection systems are becoming a necessity in our country's defense against terrorist threats that a few short years ago would have gone undetected and, worse, unimpeded.
John Long is the global sales development manager, integrated solution department, at the Radiation Measurement & Security Instruments business of Thermo Fisher Scientific. Contact him at [email protected].