The DIAMINE Landmine Detection System
G. Viesti1), M. Lunardon1), G. Nebbia1) , M. Barbui2) , M. Cinausero2), E.
Fioretto2), G. Prete2), A. Pantaleo3), G. D’Erasmo3), M. Palomba3), M. Abbrescia3),
G. Iaselli3), F. Loddo3), V. Paticchio3), T.Ranieri3), R. Trentadue3) , A. Colla4), A.
Musso4), A. Piccotti4), F. Poggio4), G. Dellacasa5), I.Lazzizzera6), P. Lecca6) , J.
Obhođaš7), D. Sudac7), K. Nađ7) , V. Valković7), A. Brusegan8), G. Lobo 8), M.
Jurkovic9), S. Hlavac9), F. Catarsi10), G Franchi10), M. A. Chianella11),D.
Galimberti11), L. Pavesi11), A. Zorat12), A. Koester13), M. Plein13), A. Merz14), H.
Schneider14), G. Vallon14)
1)
Dipartimento di Fisica and INFN Sezione di Padova, Padova, Italy 2) INFN Laboratori Nazionali di Legnaro,
Legnaro (Padova) Italy 3) Dipartimento di Fisica and INFN Sezione di Bari, Bari, Italy 4) Dipartimento di Fisica
Sperimentale and INFN Sezione di Torino, Torino, Italy 5) Università del Piemonte Orientale and INFN Gruppo
Collegato di Alessandria, Alessandria, Italy 6) Dipartimento di Fisica and INFN Gruppo Collegato di Trento,
Trento, Italy 7) Department of Experimental Physics, Ruđer Bošković Institute, Zagreb, Croatia, 8) JRC-IRMM
Geel, Belgium 9) Institute of Physics of the Slovak Academy of Science, Bratislava, Slovak Republic, 10) CAEN SpA,
Viareggio,Italy, 11) LABEN SpA, Vimodrone (Milano) Italy, 12) NeuriCam, Trento, Italy, 13) Plein&Baus
GMBH,Burscheid-Higen,Germany, 14) Vallon GMBH, Eningen,Germany
Abstract. The DIAMINE sensor makes use of the neutron backscattering techniques (NBT). The presence of a buried
land-mine causes a localized strong increase of the yield of low energy neutrons, due to the hydrogen content of the
explosive and of the plastic case of the mine. In some conditions, the hit distribution could provide an "image" of the
hidden object. Coupling of the NBT sensor with a metal detector (MD) will provide the operator with a compact device,
reducing the false alarm rate of the single sensors. The laboratory tests of the DIAMINE system demonstrate the
possibility to detect small APM up to 10 cm depth in sand. The best use of the NBT technique is presented in the frame
of the Humanitarian De-mining requirements.
confirmation detector coupled to a MD. When a fast
neutron source like 252Cf is used to irradiate the soil,
the yield of low-energy backward scattered neutrons
depends on the hydrogen content of the irradiated
volume. Therefore, to confirm the presence of the
mine, a Neutron Back-scattering (NB) sensor will
verify the presence of anomalous hydrogen
concentrations [1,2] in the target point identified by a
MD.
INTRODUCTION
A common procedure used in Humanitarian Demining operations is the localization of land-mine by
using Metal Detectors (MD), that are capable of
locating very small metal quantity, as those
characteristic of the modern Anti-Personnel Mines
(APM). However, the efficiency of Humanitarian Demining operations is generally reduced by the false
alarm rate due to the presence of metal clutter in the
soil. To overcome this problem, a sensor based on the
neutron back-scattering technique can be used as
A successful system that integrates a MD with a
NB detector has to fulfill a number of technical and
operational requirements dictated by the End User
needs. First, the total weight of the sensor head should
not be larger than 2 kg, having dimensions typical of
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© 2003 American Institute of Physics 0-7354-0149-7/03/$20.00
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possible to define a critical value of the soil moisture
above which the detection is impossible, the
thermalization properties of land-mine being
equivalent to that of the soil.
standard MD and, in any case, not exceeding 20 x 30
cm2. Moreover, the sensor should provide clear
information, as the usual MD man-machine interface
(MMI). Finally, the cost-effectiveness of this new
sensor has to be verified, comparing against the baseline of the actual operations employing the usual MD.
A specific analysis of this problem, reported in ref
4, brings us to the conclusion that the best use of the
NB technique is in countries where the soil moisture is
lower than about 10% in weight. In the above
conditions, all type of land-mines are detectable. This
is the case of arid countries, where a large part of the
world land-mine problem is localized. In other
countries, the use of the sensor might be limited to
some type of soils and/or specifically dry seasons.
Such requirements imply a number of
technological challenges to retain the performance of
the single detectors when integrated in a unique sensor
head.
In this paper, we report on the development of a
hand-held sensor, integrating the NB detector with a
MD. This work has been performed in the framework
of the DIAMINE project funded by the European
Union under the contract IST-2000-25237 [3]. The
DIAMINE Consortium integrates research bodies as
the Italian Istituto Nazionale di Fisica Nucleare, the
Institute of Physics of the Slovak Academy of Science,
the JRC-IRMM Geel, Belgium, with the companies
LABEN SpA, CAEN SpA and NeuriCam SpA from
Italy and Plein&Baus GMBH and VALLON GMBH
from Germany. LABEN is in charge of the project
coordination.
SENSOR DESCRIPTION
The current NB sensor, produced by INFN, uses a
large area (20 x 20 cm2) Multi-Wire Proportional
Chamber (MWPC) with two layers of boron carbide
(B4C) 97% enriched in 10B as neutron converters [5].
This detector was selected after an R&D phase in
which other options of thermal neutron detectors as Liglass and Resistive Plate Chambers using either B or
Gd converters were studied [3,6]. Detector prototypes
have been tested using neutron beams from the
GELINA facility at JRC-IRMM, Geel.
THE NB TECHNIQUE
The detector prototype consists basically of four
parallel electrodes: an anode wire plane, two cathodes
coated with a 3 µm enriched B4C layers and a pads
plate. The pixel resolution is 2x2 cm2. The efficiency
for low energy neutrons is determined by the
conversion efficiency of the boron layers to about
16%. Detector structures have been specifically
designed to minimize the metal content, so that it will
not disturb the standard VALLON MD coil used in the
sensor head.
Sensors based on the NB techniques suffer from a
number of intrinsic limitations. The landmine is indeed
identified only when the signal due to the hidden
object is detectable over the background due directly
to the fast neutron source and in that arising from the
soil.
The first source of background depends on the used
neutron source (typically 252Cf) and on the detector
sensitivity to gamma and fast neutrons. Particular
choice of the detector might in part influence the final
performance of the system.
The total electrodes weight is about 700 g. During
laboratory tests, electrodes are enclosed in a gas-tight,
sealed G-10 box. The final sensor head that includes
the gas NBT detector and the MD coil has been
produced by LABEN using low hydrogen content
materials. The total weight of the sensor head is about
2 kg. The NBT detector is operated with a mixture of
Ar(85%) and CO2(15%) at atmospheric pressure. A
steady gas charge will allow operation during an 8
hours shift [5].
On the contrary, the second type of background
sets intrinsic limitations to the method. The landmine
detection is possible, indeed, only when the
thermalization capability of the buried mine is
different from that of the soil, the latter being
essentially due to the soil moisture. Since the
thermalization capability is mainly determined by the
hydrogen content, the condition for the detection lies
in the hydrogen density difference between the
landmine and the surrounding soil. Moreover, each
type of mine has a well defined H density, determined
not only by the explosive charge itself, but also by the
external plastic case. It means that, for each mine, it is
Dedicated compact electronics for the MWPC
read-out has been designed by CAEN. The HV supply
and battery pack have been designed by Plein&Baus.
MD coil and electronics are provided by VALLON.
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The on board computing is under construction by
NeuriCam.
qualitatively the possibility of detecting APM in dry
soil up to 10 cm depth. Quantitatively, the
experimental data have been used to validate the
extensive Monte Carlo calculations presented in the
next section, that have been used, in turn, to determine
the performance of the sensor in different conditions.
Moreover, the hit distributions as a function of the
MWPC wire numbers has been measured to
demonstrate the possibility of obtaining information on
the buried object. A typical background subtracted hit
distribution is shown in Fig.2. A gaussian fit to the
experimental data gives the centroid in the correct
mine position but a large width compared with the 8
cm diameter of the APM.
LABORATORY SENSOR TESTS
Count Rate (a.u.)
In a first phase, laboratory tests were performed to
verify the performance of the detector. In particular,
samples of High Density Polyethylene (HDP) of
different weight were employed to verify the linearity
of the response with the hydrogen quantity and the
measuring geometry. It is found that, as expected, the
counting rate is affected mainly by the variation of the
solid angle under which the sample is irradiated and is
proportional to the quantity of hydrogen present in the
sample. Since the background rate depends also on the
source detector distance, the optimization of the
signal-to-noise ratio is reached when the source is
located close to the inspected object. It means that for
de-mining operation when the sensor stand off
distance is about 10 cm, the best results are obtained
when the source is lowered from the sensor to the soil
surface. This is possible only when the sensor is used
in a confirmation mode, the suspect point being
already identified by the MD scanning.
1,2
1
0,8
0,6
0,4
0,2
0
FIGURE 2. Hit distribution (counts versus wire group
number) of the dummy APM for 5 cm depth. Stand-off
distance is 12 cm. The background due to the bare soil has
been subtracted.
0
5
10
15
20
Mine Depth (cm)
MONTE CARLO SIMULATIONS
An extensive Monte Carlo simulation campaign
has been performed to assess the viability of the
method as a function of the type of buried land-mine
(TMA-3, PMA-1, PMA-2, PMA-3), the detector stand
off distance, the measuring geometry, the mine depth
(5-20cm) and the soil moisture (0-20% in weight).
Standard soil with homogeneous distribution of
moisture was considered. More than 100 different
simulations have been produced up to now, by using
the GEANT3 package software.
FIGURE 1. Count rate versus depth as measured for APM
dummy in laboratory conditions, when the background due
to the bare soil is subtracted. The stand off distance is 12 cm.
Statistical uncertainties are smaller than the marker size.
In a second phase, test were performed using a
dummy anti-person landmine (APM) provided by the
Cape Town University in the framework of a IAEA
Coordinated Research project on Humanitarian Demining. Experimental results were obtained with a
5x104 neutron/s 252Cf source and a soil box containing
sand having moisture of 3% in weight. Results are
shown in Fig.1 in term of the counting rate versus
APM depth, for confirmation geometry and stand off
distance of about 12 cm. The reported data confirm
Results of simulations were then analyzed using a
software program developed for the sensor ManMachine Interface, that reflects the proposed use of the
sensor. The key point is the definition of the
background (i.e soil without mine) that have to be
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subtracted from the data file obtained by inspecting the
suspect point as defined by the MD scanning.
realistic times when the so-called confirmation
geometry is used.
In a first phase, by integrating over the whole
detector, the net total count is obtained just by
subtraction of the current background from the actual
measurement. If the net signal is positive, a statistical
test is performed to ascertain if the detection can be
declared with a 0.996 confidence level. The minimum
time required to pass the test is defined as the
minimum confirmation time. In this procedure the
background is assumed to be known. At fixed times,
the distribution of the net hits on the detector surface is
inspected and the area for the optimum signal to noise
ratio is determined. This fact reflects the experimental
observation, confirmed by Monte Carlo simulations,
that the background is characterized by a relatively flat
distribution of the counts over the detector surface
whereas the buried APM exhibits a bell-shaped
distribution. The definition of this restricted area
improves the signal to noise ratio, reducing the
measurement time.
In the meantime, the performance of the NB
technique has been studied by Monte Carlo
simulations. Results, validated by laboratory data,
foresee the possibility of detecting APM in realistic
times for burial depths up to 10 cm and soil moisture
up to 10% in weight. The possibility of detecting landmines up to the limit of 20 cm depth need to be
further investigated. Limitation of the NBT sensor use
to a well defined range of soil moisture seems to be an
intrinsic fact characterizing the technique.
Furthermore, specific soil moisture measurements
performed within the DIAMINE project in mined
areas in Balkans [4], have revealed that in several type
of soils the soil moisture exhibits a large small-scale
variability. Such effects need to be further studied,
since the local variation of the soil moisture might
cover or mimic the net counts due to the buried landmine. The above points will be the subject of further
work of the DIAMINE Consortium in the near future.
The determination of the minimum confirmation
time is essential in establish the viability of such
system. Indeed, it has been suggested [7] that after the
MD inspection, the confirmation time should not be
larger of 30s to be of effective benefit in Humanitarian
De-mining operations respect to the common prodding
procedure. Results form Monte Carlo simulations for
some APM mines are summarized in Table I for soil
moisture of 5% in weight, stand off distance of 10 cm
and 5x105 neutron/s 252Cf source.
REFERENCES
1. Brooks, F.D. & Buffler, A. Detection of Plastic Land
Mines by Neutron Backscattering, 6th International
Conference on Applications of Neutron Science, June
1999, Crete, Greece.
2. Datema, C.P., Bom, V.R., van Eijk, C.W.E. Landmine
detection with the neutron backscattering method, IEEE
Transactions on Nuclear Science 48, 1087-1091 (2001).
TABLE I. Predicted confirmation times for APM
buried at 10 cm depth. The background due to the
bare soil is assumed to be known.
APM
TIME (s)
PMA-1
8
PMA-2
15
PMA-3
14
3. See also Nebbia, G. DIAMINE (Detection and Imaging
of Anti-personnel Landmines by Neutron Backscattering
Technique),
4th International Symposium on
Technology and Mine Problem, Naval Postgraduate
School, Monterey, CA, USA. April 21-25. 2002.
4. Obhođaš, J et al., The soil moisture and its relevance to
the landmine detection by neutron backscattering
technique, V International Topical Meeting on Industrial
Radiation and Radioisotope Measurement Applications,
June 2002, Bologna ,Italy and to be published on Nucl.
Instr. Meth. B.
CONCLUSIONS
A new hand held landmine sensor is being
developed within the DIAMINE project, based on the
integration of a neutron backscattering sensor with a
metal Detector. After two years of work, important
results have been reached from the hardware side. The
sensor head has been designed and major components
have been tested in laboratory conditions,
demonstrating the possibility of detecting APM in
5. Fioretto, E et al., Neutron back-scattering sensor for the
detection of land mines, ibidem.
6. Piccotti, A et al., RPC for thermal neutron detection,
ibidem.
7. Blagden, P, Geneva International Center for Humanitarian
De-mining, Private Communication, 2002.
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