- Email: [email protected]
Development of the EURITRACK tagged neutron inspection system
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 261 (2007) 295–298 www.elsevier.com/locate/nimb
Development of the EURITRACK tagged neutron inspection system B. Perot a,*, C. Carasco a, S. Bernard a, A. Mariani a, J.-L. Szabo b, E. Mercier b, G. Sannie b, G. Viesti c, G. Nebbia c, S. Pesente c, M. Lunardon c, S. Moretto c, D. Fabris c, A. Zenoni d, G. Bonomi d, A. Donzella d, A. Fontana e, G. Boghen e, V. Valkovic f, D. Sudac f, M. Moszynski g, T. Batsch g, M. Gierlik g, D. Woski g, W. Klamra h, P. Isaksson h, P. Le Tourneur i, M. Lhuissier i, A. Colonna j, C. Tintori j, P. Peerani k, V. Sequeira k, M. Salvato k a
i
Commissariat a` l’Energie Atomique, 13108 St Paul-lez-Durance, France b Commissariat a` l’Energie Atomique, 91191 Gif-Sur-Yvette, France c INFN and Universita` di Padova, Via Marzolo 8, I-35131 Padova, Italy d INFN and Universita` di Brescia, 38 Via Branze 25123 Brescia, Italy e INFN and Universita` di Pavia, 6 Via Bassi 27100 Pavia, Italy f Institute Ruder Boskovic, 54 Bijenicka c., 10000 Zagreb, Croatia g Soltan Institute for Nuclear Studies, PL 05-400 Otwock-Swierk, Poland h Royal Institute of Technology, 10691 Stockholm, Sweden EADS-SODERN, 20 Av. Descartes, 94451 Limeil-Bre´vannes Cedex, France j CAEN S.p.A., 11 Via Vetraia, 55049 Viareggio, Italy k European Commission, Joint Research Centre, I-21020 Ispra,Italy Available online 3 April 2007
Abstract The EURopean Illicit TRAfficing Countermeasures Kit (EURITRACK) project is part of the 6th European Union Framework Program. It aims at developing a Tagged Neutron Inspection System (TNIS) to detect illicit materials, such as explosives and narcotics, in cargo containers. Fast neutron induced reactions produce specific gamma-rays used to determine the chemical composition of the inspected material. The associated particle technique is employed to precisely locate the interaction points of the neutrons. A new deuterium–tritium neutron generator has been developed, including a pixelized alpha particle detector. The TNIS also comprises high-efficiency fast neutron and gamma-ray detectors, a dedicated front-end electronics and an integrated software to entirely drive the system and automatically process the data. Most components have been integrated during last months at Institute Ruder Boskovic, in Zagreb, Croatia. An overview of the TNIS and of its preliminary performances is presented. 2007 Elsevier B.V. All rights reserved. PACS: 28.20.V; 29.30.Kv; 89.20.Bb; 89.40.Cc Keywords: EURITRACK; Associated particle technique; Fast neutron inspection; Explosive detection
1. Introduction Non-intrusive inspection of cargo containers has become a key issue in the fight against terrorism. At present *
Corresponding author. Tel.: +33 442254048; fax: +33 442252367. E-mail address: [email protected] (B. Perot).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.03.073
time, controls are mainly based on X-ray or gamma-ray scanners, which provide the shape and density of the transported goods. Fast neutrons can be additionally employed to deduce information about their elemental composition [1]. Gamma-rays following fast neutron induced reactions are used to characterize carbon, oxygen and nitrogen, which are major components of explosives or narcotics.
296
B. Perot et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 295–298
In addition, the associated particle technique [2] makes it possible to inspect a specific region of the container, thus improving the selectivity of the method and the signal-tonoise ratio. The 3H(2H,n)4He fusion reaction is used to produce a 14-MeV neutron and an alpha particle, which are emitted nearly back to back, direction and time-offlight of the neutron being then deduced from the measurement of the associated alpha particle. The Tagged Neutron Inspection System (TNIS) concept has been studied in Europe during the last few years [3–5]. The EURITRACK project aims at developing a second generation TNIS for cargo containers to be used in connection with existing X-ray scanners [6]. It is proposed that the X-ray scan would determine the suspect voxel inside the cargo container to be inspected by the TNIS. Consequently it would be not necessary to scan the entire container with neutron beams. A general view of the system is presented in Fig. 1. The transportable sealed-tube neutron generator includes a 8 · 8 matrix of YAP:Ce alpha particle detectors coupled to a multi-anode photomultiplier [7]. High-efficiency 500 · 500 and 500 · 500 · 1000 NaI(Tl) detectors are located around the cargo container to detect the neutron-induced gamma-rays. The neutron attenuation across the container is measured with a 500 · 500 BC501A liquid scintillation detector, which discriminates neutron and gamma from pulse-shape and time-of-flight information. These detectors are equipped with fast photomultiplier tubes to achieve nanosecond time resolution [8]. A dedicated front-end electronics is used to verify coincidences between any alpha and gamma-ray detectors [9]. The partners of the EURITRACK project developed and tested the TNIS components during year 2005 [6–8]. Their integration into a first version of the TNIS, without gamma-ray detectors shielding, was recently completed at Institute Ruder Boskovic (IRB) in Zagreb, Croatia, and followed by detection tests. The design and expected per-
formances of the system were previously studied using Monte Carlo simulation [10,11], showing in particular that the TNIS can detect, in 10-min, a 100-kg block of TNT explosive hidden in a container fully filled with iron freight of 0.2 g/cm3 mean density, which is the reference case of the EURITRACK project. In the following, we present the laboratory verification of the expected sensitivity. 2. Experimental results Fig. 2 shows the experimental setup during some of the experimental tests. The presence of the explosive was simulated in this particular experiment by an equivalent mixed target composed of liquid nitrogen, graphite and water, whereas the container is loaded with iron boxes filled with wire balls. More experimental tests were also performed by using paper that exhibits the same C/O ratio of TNT. Fig. 3 shows the alpha–gamma coincidence time spectrum and the random-background-subtracted energy spectrum of the target, for long and short measurement times. One can clearly identify on the time spectrum the main features of the setup. The first peak, which is used as the zero time reference, corresponds to the neutron generator itself. Events at negative time are due to random coincidences. The second peak at about 7–8 ns is related to the first walls of both the cargo container and the iron box located in front of the target. Then the signal of the wire balls filling can be observed, up to a small peak near 19–20 ns due to the second wall of the box. The main peak centred at 25– 26 ns corresponds to the nitrogen flask whereas the smaller peak at 34 ns comes from graphite and water, which appear in the same time window. Note that with a real 100-kg TNT block, nitrogen, carbon and oxygen would produce a single time peak with different relative gamma-ray yields in the energy spectra. The present experimental setup enhances, indeed, the signal of the nitrogen flask, which is closer to the neutron source and shields graphite and
Fig. 1. The EURITRACK tagged neutron inspection system.
B. Perot et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 295–298
Fig. 2. The mixed target, including a liquid nitrogen flask, graphite blocks and water bottles, placed in the centre of a container fully filled with iron boxes. Boxes are contain wire balls to achieve a 0.2 g/cm3 mean iron density.
water from the tagged neutron beam. Finally, after another small peak at 41–42 ns, which is related to the first wall of
297
the iron box located after the target, the last peak near 53–54 ns marks the second walls of this box and of the cargo container. The full-energy peaks of nitrogen (2.3-, 3.7-, 4.4-, 5.1and 7.0 MeV), carbon (4.4 MeV) and oxygen (2.7-, 3.7-, 6.1- and 7.1 MeV) and associated escape peaks are either clearly visible or can be guessed in the long measurement energy spectrum. The peaks of aluminium (1.8-, 2.2- and 3.0 MeV), which mainly constitutes the liquid nitrogen dewar, are also present. An unfolding algorithm, using a library of pure elements energy spectra, is used to separate the relative contributions of all elements. Despite statistical uncertainties, it is possible to discern these signatures also in the 10-min energy spectrum of Fig. 3. Given that the random background increases with the square of the total neutron emission rate, whereas the useful signal increases linearly, the signal-to-randombackground ratio is logically 4 times smaller than in the long measurement being the rate about 4 times higher: 3.107 neutrons/s versus 7.106 neutrons/s. Note that at 3.107 neutrons/s, the total count rate of all the gamma-ray detectors is close to 105 counts/s, when the low energy threshold of the discriminators is set at about 2 MeV.
Fig. 3. Alpha–gamma coincidence time spectra (left column) and random-background-subtracted energy spectra (right column) of the mixed target in Fig. 2. In the time spectra, the investigated part of the container is shown in grey whereas the hatched area corresponds to the random background region. A 760-min long measurement at 7.106 neutrons/s total neutron emission is presented to ease peaks recognition (top row) and a 10-min long measurement at 3.107 neutrons/s illustrates the TNIS capability to detect the illicit item in a realistic time (bottom row).
298
B. Perot et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 295–298
3. Conclusion The tests of the EURITRACK TNIS performed at IRB Zagreb demonstrate its ability to detect, in 10-min, a multielement sample hidden in a container fully-filled with iron goods of 0.2 g/cm3 mean density. The alpha–gamma coincidence time spectrum reveals a strong heterogeneity in the centre of the container, where carbon, oxygen and nitrogen have been identified in the energy spectrum. Energy spectra of the other regions of the container, which are filled with iron, show no significant peak above 2 MeV. This confirms the presence of the hidden goods in the cargo. An unfolding algorithm determines the relative contributions of the elements of interest (C, N, O, Al, Fe, etc.), allowing material identification. Several tests with other cargo configurations have been performed at IRB to determine the TNIS performances in a wider range of application and find out the appropriate decision making procedures. The TNIS will be integrated in the end of year 2006 in CEA Saclay (France), on a mechanical portal that will allow a fine positioning of the neutron generator and detectors around the inspected truck. This will be the last laboratory step before
the final demonstration, planned during 2007, in a European seaport. Acknowledgement This work is supported by the European Union through the EURopean Illicit TRAfficking Countermeasures Kit project (FP6-2003-IST-2 Proposal/Contract 511471). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
T. Gozani, Nucl. Instr. and Meth. B 213 (2004) 460. V. Valkovic et al., Nucl. Instr. and Meth. B 76 (1969) 29. G. Viesti et al., Nucl. Instr. and Meth. B 241 (2005) 748. G. Nebbia et al., Nucl. Instr. and Meth. A 533 (2004) 575. S. Pesente et al., Nucl. Instr. and Meth. A 531 (2004) 657. B. Perot et al., Proc. SPIE Vol. 6213, Non-Intrusive Inspection Technologies, p. 621305. G. Nebbia et al., IEEE Nucl. Sci. Symp. Conf. Rec. 1 (2005) 134. M. Gierlik et al., IEEE Nucl. Sci. Symp. Conf. Rec. 3 (2005) 1508. M. Lunardon et al., Nucl. Instr. and Meth. B, these Proceedings, doi:10.1016/j.nimb.2007.03.072. G. Perret et al., J. Phys.: Conf. Ser. 41 (2006) 375. A. Donzella et al., J. Phys.: Conf. Ser. 41 (2006) 233.
Nuclear Instruments and Methods in Physics Research B 261 (2007) 295–298 www.elsevier.com/locate/nimb
Development of the EURITRACK tagged neutron inspection system B. Perot a,*, C. Carasco a, S. Bernard a, A. Mariani a, J.-L. Szabo b, E. Mercier b, G. Sannie b, G. Viesti c, G. Nebbia c, S. Pesente c, M. Lunardon c, S. Moretto c, D. Fabris c, A. Zenoni d, G. Bonomi d, A. Donzella d, A. Fontana e, G. Boghen e, V. Valkovic f, D. Sudac f, M. Moszynski g, T. Batsch g, M. Gierlik g, D. Woski g, W. Klamra h, P. Isaksson h, P. Le Tourneur i, M. Lhuissier i, A. Colonna j, C. Tintori j, P. Peerani k, V. Sequeira k, M. Salvato k a
i
Commissariat a` l’Energie Atomique, 13108 St Paul-lez-Durance, France b Commissariat a` l’Energie Atomique, 91191 Gif-Sur-Yvette, France c INFN and Universita` di Padova, Via Marzolo 8, I-35131 Padova, Italy d INFN and Universita` di Brescia, 38 Via Branze 25123 Brescia, Italy e INFN and Universita` di Pavia, 6 Via Bassi 27100 Pavia, Italy f Institute Ruder Boskovic, 54 Bijenicka c., 10000 Zagreb, Croatia g Soltan Institute for Nuclear Studies, PL 05-400 Otwock-Swierk, Poland h Royal Institute of Technology, 10691 Stockholm, Sweden EADS-SODERN, 20 Av. Descartes, 94451 Limeil-Bre´vannes Cedex, France j CAEN S.p.A., 11 Via Vetraia, 55049 Viareggio, Italy k European Commission, Joint Research Centre, I-21020 Ispra,Italy Available online 3 April 2007
Abstract The EURopean Illicit TRAfficing Countermeasures Kit (EURITRACK) project is part of the 6th European Union Framework Program. It aims at developing a Tagged Neutron Inspection System (TNIS) to detect illicit materials, such as explosives and narcotics, in cargo containers. Fast neutron induced reactions produce specific gamma-rays used to determine the chemical composition of the inspected material. The associated particle technique is employed to precisely locate the interaction points of the neutrons. A new deuterium–tritium neutron generator has been developed, including a pixelized alpha particle detector. The TNIS also comprises high-efficiency fast neutron and gamma-ray detectors, a dedicated front-end electronics and an integrated software to entirely drive the system and automatically process the data. Most components have been integrated during last months at Institute Ruder Boskovic, in Zagreb, Croatia. An overview of the TNIS and of its preliminary performances is presented. 2007 Elsevier B.V. All rights reserved. PACS: 28.20.V; 29.30.Kv; 89.20.Bb; 89.40.Cc Keywords: EURITRACK; Associated particle technique; Fast neutron inspection; Explosive detection
1. Introduction Non-intrusive inspection of cargo containers has become a key issue in the fight against terrorism. At present *
Corresponding author. Tel.: +33 442254048; fax: +33 442252367. E-mail address: [email protected] (B. Perot).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.03.073
time, controls are mainly based on X-ray or gamma-ray scanners, which provide the shape and density of the transported goods. Fast neutrons can be additionally employed to deduce information about their elemental composition [1]. Gamma-rays following fast neutron induced reactions are used to characterize carbon, oxygen and nitrogen, which are major components of explosives or narcotics.
296
B. Perot et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 295–298
In addition, the associated particle technique [2] makes it possible to inspect a specific region of the container, thus improving the selectivity of the method and the signal-tonoise ratio. The 3H(2H,n)4He fusion reaction is used to produce a 14-MeV neutron and an alpha particle, which are emitted nearly back to back, direction and time-offlight of the neutron being then deduced from the measurement of the associated alpha particle. The Tagged Neutron Inspection System (TNIS) concept has been studied in Europe during the last few years [3–5]. The EURITRACK project aims at developing a second generation TNIS for cargo containers to be used in connection with existing X-ray scanners [6]. It is proposed that the X-ray scan would determine the suspect voxel inside the cargo container to be inspected by the TNIS. Consequently it would be not necessary to scan the entire container with neutron beams. A general view of the system is presented in Fig. 1. The transportable sealed-tube neutron generator includes a 8 · 8 matrix of YAP:Ce alpha particle detectors coupled to a multi-anode photomultiplier [7]. High-efficiency 500 · 500 and 500 · 500 · 1000 NaI(Tl) detectors are located around the cargo container to detect the neutron-induced gamma-rays. The neutron attenuation across the container is measured with a 500 · 500 BC501A liquid scintillation detector, which discriminates neutron and gamma from pulse-shape and time-of-flight information. These detectors are equipped with fast photomultiplier tubes to achieve nanosecond time resolution [8]. A dedicated front-end electronics is used to verify coincidences between any alpha and gamma-ray detectors [9]. The partners of the EURITRACK project developed and tested the TNIS components during year 2005 [6–8]. Their integration into a first version of the TNIS, without gamma-ray detectors shielding, was recently completed at Institute Ruder Boskovic (IRB) in Zagreb, Croatia, and followed by detection tests. The design and expected per-
formances of the system were previously studied using Monte Carlo simulation [10,11], showing in particular that the TNIS can detect, in 10-min, a 100-kg block of TNT explosive hidden in a container fully filled with iron freight of 0.2 g/cm3 mean density, which is the reference case of the EURITRACK project. In the following, we present the laboratory verification of the expected sensitivity. 2. Experimental results Fig. 2 shows the experimental setup during some of the experimental tests. The presence of the explosive was simulated in this particular experiment by an equivalent mixed target composed of liquid nitrogen, graphite and water, whereas the container is loaded with iron boxes filled with wire balls. More experimental tests were also performed by using paper that exhibits the same C/O ratio of TNT. Fig. 3 shows the alpha–gamma coincidence time spectrum and the random-background-subtracted energy spectrum of the target, for long and short measurement times. One can clearly identify on the time spectrum the main features of the setup. The first peak, which is used as the zero time reference, corresponds to the neutron generator itself. Events at negative time are due to random coincidences. The second peak at about 7–8 ns is related to the first walls of both the cargo container and the iron box located in front of the target. Then the signal of the wire balls filling can be observed, up to a small peak near 19–20 ns due to the second wall of the box. The main peak centred at 25– 26 ns corresponds to the nitrogen flask whereas the smaller peak at 34 ns comes from graphite and water, which appear in the same time window. Note that with a real 100-kg TNT block, nitrogen, carbon and oxygen would produce a single time peak with different relative gamma-ray yields in the energy spectra. The present experimental setup enhances, indeed, the signal of the nitrogen flask, which is closer to the neutron source and shields graphite and
Fig. 1. The EURITRACK tagged neutron inspection system.
B. Perot et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 295–298
Fig. 2. The mixed target, including a liquid nitrogen flask, graphite blocks and water bottles, placed in the centre of a container fully filled with iron boxes. Boxes are contain wire balls to achieve a 0.2 g/cm3 mean iron density.
water from the tagged neutron beam. Finally, after another small peak at 41–42 ns, which is related to the first wall of
297
the iron box located after the target, the last peak near 53–54 ns marks the second walls of this box and of the cargo container. The full-energy peaks of nitrogen (2.3-, 3.7-, 4.4-, 5.1and 7.0 MeV), carbon (4.4 MeV) and oxygen (2.7-, 3.7-, 6.1- and 7.1 MeV) and associated escape peaks are either clearly visible or can be guessed in the long measurement energy spectrum. The peaks of aluminium (1.8-, 2.2- and 3.0 MeV), which mainly constitutes the liquid nitrogen dewar, are also present. An unfolding algorithm, using a library of pure elements energy spectra, is used to separate the relative contributions of all elements. Despite statistical uncertainties, it is possible to discern these signatures also in the 10-min energy spectrum of Fig. 3. Given that the random background increases with the square of the total neutron emission rate, whereas the useful signal increases linearly, the signal-to-randombackground ratio is logically 4 times smaller than in the long measurement being the rate about 4 times higher: 3.107 neutrons/s versus 7.106 neutrons/s. Note that at 3.107 neutrons/s, the total count rate of all the gamma-ray detectors is close to 105 counts/s, when the low energy threshold of the discriminators is set at about 2 MeV.
Fig. 3. Alpha–gamma coincidence time spectra (left column) and random-background-subtracted energy spectra (right column) of the mixed target in Fig. 2. In the time spectra, the investigated part of the container is shown in grey whereas the hatched area corresponds to the random background region. A 760-min long measurement at 7.106 neutrons/s total neutron emission is presented to ease peaks recognition (top row) and a 10-min long measurement at 3.107 neutrons/s illustrates the TNIS capability to detect the illicit item in a realistic time (bottom row).
298
B. Perot et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 295–298
3. Conclusion The tests of the EURITRACK TNIS performed at IRB Zagreb demonstrate its ability to detect, in 10-min, a multielement sample hidden in a container fully-filled with iron goods of 0.2 g/cm3 mean density. The alpha–gamma coincidence time spectrum reveals a strong heterogeneity in the centre of the container, where carbon, oxygen and nitrogen have been identified in the energy spectrum. Energy spectra of the other regions of the container, which are filled with iron, show no significant peak above 2 MeV. This confirms the presence of the hidden goods in the cargo. An unfolding algorithm determines the relative contributions of the elements of interest (C, N, O, Al, Fe, etc.), allowing material identification. Several tests with other cargo configurations have been performed at IRB to determine the TNIS performances in a wider range of application and find out the appropriate decision making procedures. The TNIS will be integrated in the end of year 2006 in CEA Saclay (France), on a mechanical portal that will allow a fine positioning of the neutron generator and detectors around the inspected truck. This will be the last laboratory step before
the final demonstration, planned during 2007, in a European seaport. Acknowledgement This work is supported by the European Union through the EURopean Illicit TRAfficking Countermeasures Kit project (FP6-2003-IST-2 Proposal/Contract 511471). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
T. Gozani, Nucl. Instr. and Meth. B 213 (2004) 460. V. Valkovic et al., Nucl. Instr. and Meth. B 76 (1969) 29. G. Viesti et al., Nucl. Instr. and Meth. B 241 (2005) 748. G. Nebbia et al., Nucl. Instr. and Meth. A 533 (2004) 575. S. Pesente et al., Nucl. Instr. and Meth. A 531 (2004) 657. B. Perot et al., Proc. SPIE Vol. 6213, Non-Intrusive Inspection Technologies, p. 621305. G. Nebbia et al., IEEE Nucl. Sci. Symp. Conf. Rec. 1 (2005) 134. M. Gierlik et al., IEEE Nucl. Sci. Symp. Conf. Rec. 3 (2005) 1508. M. Lunardon et al., Nucl. Instr. and Meth. B, these Proceedings, doi:10.1016/j.nimb.2007.03.072. G. Perret et al., J. Phys.: Conf. Ser. 41 (2006) 375. A. Donzella et al., J. Phys.: Conf. Ser. 41 (2006) 233.