Gross R., Sidorenko A., Tagirov L. Nanoscale Devices

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Surface Acoustic Wave Studies for Chemical and Biological Sensors 11

highly sensitive sensor for different gas mixtures and/or contents can be

devised. For this purpose, an array of differently sensitized pixels (single

sensors) is deposited in a checkerboard like manner in between the four

senor transducers. The different pixels aught to have a different response

for a given gas or gas mixture (see Fig. 6). The spatially resolving SAW

chip employing the tapered transducers is the used to read out the

accumulated sensor signal for a set of pixels in either a row or a column.

Fig. 7. Spatially resolving SAW sensor employing tapered SAW transducers as

described in the text. The active area consists of an array of different sensitized

pixels, each having a specific response (numbers on squares) to a given reagent.

The SAW can read out the accumulated signal (Σ) of, in this case three pixels at a

time.

In Fig. 7, we depict the idea of such a sensor chip with many different

pixels. Each pixel exhibits a specific sensitivity for a given gas mixture.

This sensitivity results in a SAW sensor signal like attenuation and/or phase

change. In the figure, we have denoted the sensor signal for a given gas

mixture by the numbers superimposed to the pixels. The read-out SAW

signal is then given by the accumulated signals for a single row or column,

respectively. In the figure, we have denoted these accumulated signals by

the sum sign and the arithmetic sum of the different rows and columns.

In Fig. 8, finally, we propose a display technique for such sensors,

especially well suited for human inspectors. Humans are very good in

pattern recognition, hence we convert the sum signals of figure 7 into a

polar diagram, for instance, resulting in an easily recognizable pattern for a

given gas mixture. A similar technique had been described in [6]. There,

however, a gas chromatograph has been used as a sensor.

12 A. Müller, A. Darga, A. Wixforth

Fig. 8. Proposed readout scheme for the sensor depicted in Fig. 7. The accumulated

sensor signals (S) are plotted in a polar-type diagram, providing an easily

recognizable pattern for a human inspector.

In summary, we have described a highly sensitive sensor scheme for

different external parameters. We use surface acoustic waves which can

interact with such external parameters, altering the propagation parameters

of the SAW. Such parameters may be conductivity changes due to

illumination, adsorption, intercalation etc., or more direct measurements

like mass loading of the surface. To increase the sensitivity for gas

adsorption, we have used functionalized mesoporous zeolite thin films,

which can be used as sensor pixels on our chip.

The authors thank T. Bein, and J.P. Kotthaus, CENS, Munich for their

continuous support and many useful discussions. Financial support of the

Bayerische Forschungsstiftung under the program FORNANO, and support

of Advalytix AG, Brunnthal, Germany is gratefully acknowledged.

References

1. Auld BA (1973) Acoustic Fields and Waves in Solids. VI, John Wiley & Sons,

Toronto

2. Ingebrigtsen K A (1969). J Appl Phys 40:2681; Ingebrigtsen KA Jr (1970).

Appl Phys 41:454

3. Farnell GW, Cermak IA, Silvester P, Wang SK (1970). IEEE Transactions on

Sonics and Ultrasonics Su27:188

4. Wixforth A, Kotthaus JP, Weimann G (1986). Phys Rev Lett 56:2104

5. Streibl M, Beil F, Wixforth A, Kadow C, Gossard AC (1999). Proc of IEEE

International Ultrasonics Symposium

6. Staples EJ (1999) Electronic Nose Simulation of Olfactory Response

Containing 500 Orthogonal Sensors in 10 Seconds. Proceedings of the IEEE

Ultrasonics Frequency Control and Ferroelectrics Symposium, Lake Tahoe,

CA, Oct. 18-21

Surface Acoustic Wave Studies for Chemical and Biological Sensors 13

7. Streibl M, Govorov AO, Wixforth A, Kotthaus JP, Kadow C, Gossard AC

(2000). Physica E 6:255-259

8. Wixforth A (2000) International Journal of High Speed Electronics and

Systems. World Scientific Publishing Company 10:1193-1227

9. Ballantine JS, White RM, Martin SJ, Ricco AJ, Zellers ET, Frye GC, Wohltjen

H (1996) Acoustic Wave Sensors. Academic Press, NY

10. Wessa T, Küppers S, Rapp M, Reibel J (2000). Sensors and Actuators B

Special issue of Prof Göpel in memoriam, 70:203-213

The Experience of Utilizing the Explosives

Detection System on the Basis of Neutron

Y. Olshansky

, A. Vishnevkin

, A. Sorokin

, A. Vikdorovich

, A. Golovin

E. Stepanov

Scientific & Technical Center “RATEC”, St Petersburg 193079, Russia

“Pulkovo” Aviation enterprise, Saint-Petersburg, Russia

Abstract: The security system utilizing the explosives detection based on the

neutron radiation analysis is described. The system successfully

operates in the Pulkovo airport, St. Petersburg, Russia, since spring

2003.

Keywords: explosive detection, thermal-neutron analysis

Because of tragic events during the last twenty years on hijacking and

explosion of passenger aircrafts, the Russian Federation laws prescribe

rigid security requirements to preflight inspection of aircraft crew members,

maintenance staff, air passengers, carry-on baggage, check-in baggage,

mail, cargo and on-board load. According to these requirements each

airport has to organize 100% preflight inspection of the passenger baggage

for the purpose of detection of forbidden objects and substances. This led to

significant re-organization of preflight inspection, as many airports of the

former Soviet Union had been built long before the new security

requirements, and they were not adjusted to operate in such rigid

conditions.

This article deals with a new approach to organization of the aviation

security systems in the Pulkovo airport (St. Petersburg, Russia). Pulkovo is

the main airport of the second largest city in the country – St. Petersburg.

R. Gross et al. (eds.), Nanoscale Devices - Fundamentals and Applications, 15–21.

at the Airport “Pulkovo” in St.-Petersburg

Radiation Analysis Together with X-Ray Units

16 Y. Olshansky, A. Vishnevkin, A. Sorokin, et al.

Nowadays Pulkovo has two terminals: Pulkovo-1 services domestic

flights, in particular to the North Caucasus region, and Pulkovo-2 is fully

used for international flights.

The rigid security requirements and necessity to inspect 100% of the

baggage called for a serious re-evaluation of the available equipment by the

aviation security service. The checking lines must meet the security

requirements and provide for efficient and convenient inspection. A task of

development of fundamentally new checking lines was realized. Special

attention was paid to stable detection of explosives, especially plastic

explosives, disregarding of their type, form and masking.

To realize this purpose it was decided to take a range of administrative

and technical measures. First of all it was decided to organize the doorway

inspection of all baggage (check-in and carry-on) prior to checking-in. This

allows inspecting all baggage of a passenger in his/her presence, and if

something suspicious is found in the baggage, the situation can be clarified

right on the spot.

The actual inspection of a baggage was split into two phases. In the first

phase an operator with the help of an X-ray unit carries out standard

inspection of the baggage for the presence of forbidden objects. If inside the

carry-on or check-in baggage there are suspicious objects, similar by

density to explosives, then this baggage is sent to the second phase of

inspection. In the second phase the thermal neutron radiation analysis

(TNA) detection system is used. It was developed by the Scientific

Technical Center RATEC (St. Petersburg, Russia), model EDS-5101

(Explosive Detection System).

In both Russia and the United States for the last fifteen years there have

been attempts to develop systems for detection of explosives in the air

passengers’ baggage on the basis of thermal neutron analysis. The

explosives are identified by registration of the gamma radiation of the

nitrogen nuclei under irradiation by thermal neutrons (explosives,

especially plastic explosives, are characterized by high content of nitrogen).

However, so far these attempts have not been resulted in building the

systems feasible for a practical use in inspection of the passengers’ baggage

and other objects. The main obstacle was a considerable amount of nitrogen

in the passengers’ baggage that is not related to explosives. This led to a

great number of false alarms.

At the same time, X-ray units are aimed for registration of differences in

substance density, but this method cannot allow for stable detection of

camouflaged explosives, especially plastic sheet explosives.

Aviation security specialists generally agree that success in detection of

such explosives can be achieved only through a combination of different

technologies.

The Experience of Utilizing the Explosives Detection 17

In the Pulkovo airport this combination is introduced in two phases of

baggage inspection: in the first checking line X-ray units are used, and in

the second phase TNA systems EDS-5101 are used. It is important to note

that the thermal neutron analysis enables to look into the structure of the

baggage substances and to detect the presence or absence of explosives by a

noninvasive analysis with a high degree of probability. The EDS-5101

system uses target designation of a suspicious area obtained from an X-ray

unit. This allows to inspect not the whole content of the baggage, but only

the area where explosives were suspected, and to detect explosives with a

high degree of precision and with a low level of false alarms.

In addition, new improved algorithms have been used in the EDS-5101

system, which utilize latest developments in physics and mathematical

statistics to provide stable separation of signals from nitrogen in explosives

on nitrogen in other substances. This decreases the number of false alarms

significantly.

The likelihood of presence of suspicious objects in the check-in and

carry-on baggage is approximately 20–25%, that is, every fourth or fifth

baggage item. The time of inspection of one piece of the check-in (or carry-

on) baggage in an X-ray unit is about 5–7 seconds, the time of inspection of

suspicious check-in (or carry-on) baggage with EDS-5101 is about 12–17

seconds. Thus, one explosive detection unit can serve from two to four

usual X-ray units, and check the carry-on baggage and suspicious check-in

baggage for the presence of explosives without reduction in the inspection

line capacity. EDS-5101 can be successfully used for checking of personal

computers, photo and video cameras, mobile phones which can used to

camouflage explosives. EDS-5101 has a mode of checking the entire carry-

on baggage, if X-ray units cannot provide a clear picture of a suspicious

area against the background. In this case EDS-5101 works practically

without target designation, however, it efficiently detects explosives.

Special algorithms allow to neutralize the influence of nitrogen not related

to explosives, so that it does not practically affect the final result. It is

important that the system comes to a conclusion automatically, without an

operator.

The explosives detection system was tested in the Livermore National

Laboratory under operation of specialists from the Transport Security

Administration (USA). It received positive assessment both of the quality

of operation and the level of safety of such systems in airports. As the

testing was carried out without X-rays, it was recommended to carry out

repeated trials with an X-ray unit. For comparison, it can be said that the

level of the stray radiation from the surface of EDS unit is practically on the

level of natural background in the airport owing to special protective

material for the case of the equipment. The EDS system received a

certificate of the Sanitary Inspection (the Russian requirements to radiation

18 Y. Olshansky, A. Vishnevkin, A. Sorokin, et al.

safety conform to the international requirements). The system can work

with two types of neutron sources: neutron generator and californium

isotope Cf-252.

Fig. 1. EDS-5101 developed on the basis of the thermal neutron radiation analysis

Explosives detection system EDS-5101 has successfully passed tests and

received a certificate of the Aviation Security Department of the

Transportation Ministry of Russia. A special decree of the Transportation

Ministry of Russia recommends for the use of EDS-5101 in airports.

The first system EDS-5101 was installed in the checking line of Pulkovo-

1 airport in spring 2003. The choice of this particular terminal was

determined by several reasons: firstly, Pulkovo-1 serves flights on the

southern direction, including the North Caucasus region; these flights

require special checking and keen attention. Besides, in May-June 2003 St.

Petersburg celebrated its 300

anniversary, and an international summit was

planned for this time. Many VIP guests were invited, including leaders of

and aimed for exploiting in airports and other transport objects.

The Experience of Utilizing the Explosives Detection 19

forty-five states. Pulkovo-1 was the only airport which received the

delegations, and where every forty seconds another governmental flight was

landing. Unprecedented security measures were taken in the airport. The

explosives detection system EDS-5101 was efficiently used in Pulkovo-1

upon receiving of guests, including trials when real explosives were used at

nonstandard situations with minimal quantities of explosives. The system

operated reliably during the 300

anniversary celebration and the summit

meeting.

Fig. 2. Principle of organization of baggage inspection line exploiting the EDS-

From the very beginning the system was widely used because of many

suspicious objects in a hand baggage and check-in baggage of the air

passengers. Practically in every flight X-ray units identify objects that could

contain explosives. In such cases EDS-5101 efficiently helps operators to

check these objects without taking them apart. It is not always possible, for

example, in case of notebook accumulators, photo and video camera

batteries, etc. At present time specialists of the Scientific and Technical

Center RATEC develop an interface that will allow the operator himself to

tune the system depending on the object in question; this is needed mainly

for checking small-size objects and detecting the minimal quantities of

explosives.

5101 system based on the neutron radiation analysis.

20 Y. Olshansky, A. Vishnevkin, A. Sorokin, et al.

The Pulkovo-1 experience in using checking line with EDS-5101 has

demonstrated that introduction of the two-phase inspection allows to

separate suspicious baggage from the ordinary baggage immediately. In this

case the X-ray unit operator does not loose time on scrutinizing the

suspicious object inside carry-on (or check-in) baggage, but sends the

suspicious baggage to the second phase of inspection. This enables

minimization of the time for inspection of one unit of baggage by the X-ray

checking line. In other words, there is no point in rejecting the ordinary X-

ray systems at the first phase. X-ray is, undoubtedly, not perfect, but with

its help a suspicious area can be identified pretty fast, and the final decision

can be made later utilizing TNA. An additional advantage is that EDS-5101

can work in a special mode without target designation.

In the baggage inspection scheme it is also important to combine systems

that are based on different physical principles. Thereupon a combination of

thermal neutron analysis and X-ray is an optimal solution to baggage

inspection, where each system performs its own task and together they

combine a highly reliable, efficient and comparatively inexpensive

inspection complex.

At the beginning of 2004 RATEC was commissioned by government to

develop a special system for detecting small amounts of explosives in

cases, handbags, packages and other similar objects. By now RATEC has

developed a range of TNA systems for protection of airports, governmental

organizations, banks and special facilities from terrorist attacks with use of

explosives, radioactive and fissible materials. Systems for checking letters

and parcels have been developed, as well as a system for protecting VIP

persons. It allows fast and efficient checking of mobile phones, photo and

video cameras, dictaphones, notebooks, microphones and other similar

objects for presence of explosives, radioactive and fissible materials.

For airports with dense traffic flows RATEC currently develops an

automatic combined system with both X-ray and TNA systems for

inspection of the hand baggage. In this new system the target designation of

a suspicious area will be done automatically, which will speed up

inspection of one piece of the hand baggage.

RATEC staff develops also a TNA system for inclusion in the inspection

line for additional checking of a baggage suspicious in the first phase of

inspection.

Development of such combined systems provides large airports with the

state-of-the-art, highly efficient inspection systems.

The Experience of Utilizing the Explosives Detection 21

Table 1. EDS systems on the basis of TNA – “ready for sale” and under

# Models Systems application

1 EDS-1101 For inspecting suspicious objects, found in public places

2 EDS-2001 For VIP persons protection. Detection of minimum quantity of

explosives

3 EDS-3100

EDS-3101

For offices, State institutions, banks and various special objects

4 EDS-4100 For nuclear power stations with detecting small quantities of

special nuclear materials

5 EDS-5101 For airports and other transport objects

6 EDS-6101 For special service with detailed investigation of checked objects

7 EDS-7101 For inspecting check-in baggage of the passengers

8 EDS-8101 For inspecting cargo air and sea containers,

In conclusion, it should be emphasized that the Pulkovo airport

experience in organization of checking lines can be widely used in airports

with relatively modest traffic flows. This approach does not require serious

reconstructions and investments. It includes already available equipment to

organize efficient and reliable inspection of carry-on and check-in baggage

in the fight against the common enemy of the civilized world – terrorism.

development of RATEC.

Gross R., Sidorenko A., Tagirov L. Nanoscale Devices - Fundamentals and Applications

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