AL VENTER/Washington DC
Devastating Terrorist bomb attacks on US embassies in Kenya and Tanzania and the subsequent US retaliation against targets in Afghanistan and Sudan have rekindled fears that airliners and airports could again become a battleground. The first line of defence will be airport baggage screening systems.
In pursuit of a device that will detect terrorist bombs, the US Federal Aviation Administration has put its trust in existing technology. But there are problems, not least the fact that the average load of suitcases on an aircraft can carry an incredible diversity of objects, many of which can resemble an explosive device.
The machines being offered by the six largest manufacturers of explosives detection systems (EDS) tend only to look at the density of objects found in airline baggage or freight. None is able to analyse the chemical composition of a suspicious object. This is essential if an explosives detection device is to do more than produce false alarms.
The X-ray machines in use do not specifically indicate the presence of explosives. What is detected almost every time are anomalies or suspicious objects. Dr Curtiss Bell, FAA security and development scientist, said in 1997: "There is no incident that I can recall where an explosive detection device at any airport actually detected an explosive leading to an arrest."
It is not surprising that there is a high ratio of false alarms. Sugar, for instance, has the same density as the C-4 explosive popular with some terrorist organisations and there have been false alarms at UK airports set off by Christmas puddings, which have the same density as plastic explosives. Similarly, Hong Kong's annual Autumn Moon Festival resulted in a spate of false alarms traced to duck eggs covered with sugary lotus paste, a concoction with a molecular structure also resembling plastic explosives.
DISGUISED COMPUTERS
Effectively, this means that with few exceptions the several thousand X-ray machines installed at US airports are not always able to pick up the presence of a terrorist bomb. For instance, a "laptop computer" made of moulded plastic explosives and containing detonating circuitry could pass inspection in any airport concourse. The equipment, basically, is chemically blind; it is not able to identify specific levels of carbon, nitrogen and oxygen, the three elements which constitute almost all explosives.
The main problem facing the dozen or so small and large EDS manufacturers is that, while the FAA has certain certification requirements, there is no global or uniform "yardstick" that applies to the industry as a whole.
Evaluation requires quantification, but the companies in this field are wary of accepting a single dominant parameter because, ultimately, it might exclude their own machines. Each of the machines available have their strengths, but these often conceal inherent disadvantages.
Recently, a yardstick was proposed and temporarily accepted. Named "1 Bust", it is the ability to detect and chemically identify 1kg of concealed explosive from a distance of 1m in 1s. The result is stated in terms of the mass of explosive in kilogrammes, multiplied by the time that it takes to identify the substance. Therefore, "1 Bust" requires the device to be able to detect 100g within 10s or 10kg (a weight typical of smuggled drugs such as heroin) in 0.1s.
Irvine, California-based research and development company HiEnergy Microdevices, claims to have the solution. It has just made public details of a detection system called the GammaQuad, which uses a technique known as tagged fast neutron analysis.
The GammaQuad has shown that it can successfully and non-intrusively detect a variety of explosive-like materials such as fertiliser stashed behind obstacles like brick walls, or even thick steel or aluminium. Unlike X-ray equipment, it uses gamma rays and fast neutrons to analyse, in real time, the chemical composition of a target substance.
The machine is the brainchild of particle physicist Professor Bogdan Maglich, who says it is the first time that this type of analysis has been achieved without using a test tube. Moreover, the miniature particle accelerator used - about 0.75m long - is a fraction of the size of similar devices used in laboratories worldwide.
Working with the US Department of Energy's (DoE) Special Technologies Laboratory at Santa Barbara, California, in conjunction with the DoE's Lawrence Berkeley National Laboratory and the EG&G corporation, GammaQuad tests have demonstrated the technical feasibility of the "immediate" chemical detection of concealed substances such as explosives.
While the application of this device to airline security is obvious, its potential extends the monitoring of sealed cargo containers, or even landmine detection. The company has several prototype mine detectors in the pipeline, with field tests planned in Angola and Mozambique.
Of the companies already established in the EDS industry, only InVision Technologies of Newark, California, has machines certificated by the FAA for the inspection of airport luggage. These are the CTX5000SP and CTX5500DS, which use computerised tomography (CT)X-ray scanning technology.
The biggest drawback is that none of the machines operates in real time. Tandem CTX5500DS systems are needed to meet the suitcase-throughput requirements of the FAA. InVision's more advanced machines have an average throughput of about 675 bags an hour, with a potential of about 900/h, which, without false alarms, allows about 5.5s per suitcase. It takes about 40min to screen baggage for the average Boeing 747.
In June, InVision received a $7.2 million FAA contract representing the first half of a 16-unit order. The systems are scheduled to be shipped to major US airports by 30 September. Significantly, Dr Lowell Burnett, chief scientist of InVision subsidiary Quantum Magnetics (QM) visited HiEnergy earlier this year, accompanied by an InVision vice-president. No details of the discussions have been released.
QM is involved in research into hard-to-detect sheet explosive compounds, which might eventually piggyback into later InVision developments. The company has received two FAA orders for its QScan 500, which can scan a single baggage load of 500 litres (130 USgal). QM has also met problems, but says that its machine was "-assessed as effective" in FAA tests.
QM chief executive Dale Sheets says that, under limited conditions, the device can detect RDX, HMX and PETN, but not the most common explosive, TNT. The company is working on it, he says. HiEnergy's Maglich claims that QM is not able to measure the chemical composition of scanned substances, "-so the false alarm rate remains high", he believes. Another contender for a chemically specific detector is the artificial nose and there are at least two projects under way. At Caltech in California, an electronic "dog's nose" has achieved a thousandfold improvement in performance since the project's start two years ago. Caltech says it needs another thousandfold improvement before the device is acceptable. Scientists associated with the work, being supported by the US Defense Advanced Research Projects Agency, say it will be three to five years before the system is fielded.
The biggest problem facing the industry, says HiEnergy's Maglich, is that it relies on X-ray technology which dates from the last century. Although both the manufacturers and the FAA call these X-ray machines "explosive detectors", it is tacitly recognised, he says, that they are only detectors of possible explosives. A second, more intrusive, inspection is essential to establish whether the item is an explosive or not. "X-rays are chemically 'blind'," says the GammaQuad's inventor, adding: "Even InVision's advanced machines identify only density."
There is one type of X-ray machine that can tell whether an object consists of light or heavy chemical elements. This employs "backscatter" X-rays and is used (in conjunction with normal X-rays) in equipment produced by companies such as American Science and Engineering (AS&E) and the UK's Vivid Technologies.
In the backscatter technique, the system not only measures the X-rays that pass through the suitcase, but also those that are bounced back. The lighter the element, the more X-rays are deflected. This, in turn, allows the machine to identify an object as a possible explosive. This considerably reduces the false alarm rate, but it is still not actually detecting an explosive.
SUSPECT ANALYSIS
HiEnergy's GammaQuad overcomes the problem by either working in tandem with a normal airport baggage scanner or as a standalone system incorporating all detection techniques, including X-ray. If an object is identified as suspect by an X-ray or CT-scan, it is automatically routed to the GammaQuad, which analyses its chemical composition in real time.
To do that, says Maglich, this emerging technology (which he has dubbed "atometrics") quantitatively identifies the three prime elements - carbon, nitrogen and oxygen - on a computer graph. These show up clearly on screen, together with their relative proportions.
The GammaQuad detects only those gamma rays emitted by the explosive (or chemical or biological) substance which are hit by a neutron that occurs at precisely the same moment as the alpha particle released with the same neutron. Each chemical element bombarded by fast neutrons emits gamma rays with a unique energy spectrum. "So it provides a 'signature' of that element," Maglich adds.
He says that his system is more advanced than the chemically specific detection technique called pulsed fast neutron analysis (PFNA), under development by a subsidiary of the San Diego-based Science Applications International (SAIC) for 15 years. "They still have to produce one saleable product," he argues. The PFNA detector weighs 12t and costs $8 million, he says, claiming that the GammaQuad is much smaller and cheaper.
Interestingly, the division of SAIC responsible for developing the PFNA detector has recently been bought by the Daiwa Bank of Tokyo and Stone Capital of Dallas (36% each) and given the name of Ancore.
For the foreseeable future, X-ray machines will be the front line of defence against terrorist bombs, and their limitations will remain the principal weakness of that defence.
AUS industry source says that the FAA now believes it was possibly military plastic explosives rolled into thin sheets that were used to bring down a Pan Am Boeing 747 over Lockerbie, Scotland, a decade ago. Because the X-ray equipment which scanned the cargo and luggage was (and still is) only density-sensitive, the bomb was never detected. Earlier reports had blamed a 0.45kg charge secreted in a transistor radio. More recent theories suggest the device might have been wrapped in sheet explosive.
More disturbing is the news that some of the principal US manufacturers of X-ray airport detectors have failed FAA sheet explosive detection tests, although these are being re-evaluated with subsequent modifications. Ron Polillo of the FAA Aviation Security Research and development, says the agency will not comment on explosives detection technology capabilities as it wishes "-to keep this information from getting into the hands of the terrorist".
InVision's CTX5000SP and CTX5500 machines matched the FAA's rigorously certificated EDS parameters. The agency ordered 54 CTX5000s in December 1996 and the first eight CTX55000s earlier this year. The FAA has also ordered advanced X-ray machines from EG&G, Heimann and Vivid.
L-3 Communications, a company spun off by Lockheed Martin, is developing a CT X-ray machine to compete with InVision's. The company is aiming to halve InVision's $1 million price tag and cut scanning time substantially, but its machine recently failed FAA certification testing for the second time. Polillo says that, while L-3 failed in its first two attempts, the company's system will be coming up again for certification soon.
Source: Flight International
