Landmine Detection Method Research Articles

Varied amplitude nonlinear acoustic method of landmine detection

Acoustic methods of land mine detection are being developed for nonmetal mines where conventional electromagnetic methods fail. Nonlinear acoustic methods have shown higher sensitivity than linear methods. In previous studies, the nonlinear methods, based on interaction of two frequency waves and phase inversion of two pulses, were investigated. We propose an alternative nonlinear method based on the use of wide‐frequency pulses with different amplitude and subtraction of the normalized received signals. This method evaluates the nonlinear effects in a wide‐frequency band similar to the phase inversion method and it detects nonlinear components that are lost in the phase inversion method. In our tests, the suggested method was combined with time reversal acoustic focusing to concentrate seismic wave energy in proximity to the mine, which increased nonlinear effects. Experiments with various types of mines were conducted at Fort Belvoir using six loudspeakers in a box for excitation in the frequency band 50–500 Hz. The nonlinear mine response measured by the varied amplitude method provides the highest mine/no mine contrast among all the experiments performed using linear and nonlinear techniques. [Work was supported by the U.S. Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate.]

Phase inversion and two-frequency interaction in nonlinear time-reversal acoustic method of land mine detection

Seismic waves are known to generate a nonlinear response in soil, but data show that the presence of a mine increases the nonlinearities due to interactions of the mine and soil system. The nonlinear effects were investigated by two methods. The first, phase inversion, uses two short, broadband TRA focused signals with opposite signs. These are broadcast sequentially and the responses are added in post processing. This results in cancellation of the linear response leaving the nonlinear system components. The second method relies on two-frequency intermodulation. In this case time-reversed seismic energy at 280 and 350 Hz was used to excite the system while the response was analyzed at the sum frequency, 630 Hz. The experiments demonstrate that the presence of the mine increases nonlinearity by 12 dB for the phase-inversion method and by 6 dB for two-frequency interactions in comparison with intact sand. These results support the hypothesis that the interface between mine body and surrounding sand significantly increases the nonlinear response as compared to sand alone. Work was supported by U.S. Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate.

Multi-beam laser Doppler vibrometer for landmine detection

The method of buried landmine detection based on using elastic waves in the ground and a laser Doppler vibrometer (LDV) as a vibration sensor has shown excellent performance in field tests. To increase the speed of measurements, a multi-beam laser Doppler vibrometer (MB-LDV) was developed. The system is based on a heterodyne interferometer and is capable of simultaneously measuring the vibration of the ground at 16 points over a span of 1 m with a velocity resolution of less than 1 µm/s. Both digital in-phase and quadrature (I&Q) and analog phase-locked loop (PLL) demodulation have been used for signal processing. The MB-LDV can create a velocity image of the ground surface either in "stop-and-stare" mode or in a continuously scanning mode. The continuously scanning operation results in an increased velocity noise floor due to speckle noise. The speckle noise floor increases with the increase of the speed of the laser beam and can degrade the velocity image of a mine. To overcome the effects of speckle noise, the excitation source must provide a ground vibration velocity higher than the velocity noise floor of the vibrometer. The MB-LDV has been tested at landmine test lanes and shows the ability to detect buried landmine within a one-square-meter area in a time of less than 20 s.

Acoustic Detection of Buried Landmines Using Pulsed ESPI

Acoustic methods of landmine detection have demonstrated promising results in detecting buried landmines in laboratory and field tests. They are based on generation of vibrations of the ground and measurement of the vibration response of the ground over the area of interest. A buried landmine can be detected by analyzing spatial distribution of the ground vibration. Reliable detection of mines requires fast measurement of vibration with high spatial resolution. This work studies the application of a pulsed electronic speckle pattern interferometer (ESPI) for the vibration measurement of the ground surface in acoustic landmine detection. Experimental results are presented from laboratory experiments. The effect of the vibration of unconsolidated soil on the speckle decorrelation is discussed. Results show that pulse ESPI can create a spatial map of vibrating ground in a time equal to or shorter than a half a period of vibration and have the ability to detect buried landmines.

Effect of particle size on the vibration of plates loaded with granular material

Acoustic methods of landmine detection are emerging as reliable techniques that are especially well suited for non-metallic mines. These methods rely on the vibrations of the top plate of the mine as it responds to the acoustic excitation. The plate response is complicated by the interaction with the surrounding soil. If the loading soil is granular (e.g., sand), it is expected that particle size will influence the mine response. Experimental results related to this hypothesis are presented here. The first resonant frequency of a sand-loaded plate is measured as a function of sand mass for dry sand of various sizes covering a range from hundreds of microns to a few millimeters. For low values of sand mass, the plate resonance decreases and eventually reaches a minimum. In this regime, there is no dependence on particle size. After the minimum, the frequency increases with additional mass. In this regime, a particle size effect is observed. Models are also presented to support and explain experimental results. The results are expected to impact quantitative aspects of mine detection by acoustic means. [Work supported by ARL.]

Nonlinear acoustic techniques for landmine detection

Measurements of the top surface vibration of a buried (inert) VS 2.2 anti-tank plastic landmine reveal significant resonances in the frequency range between 80 and 650 Hz. Resonances from measurements of the normal component of the acoustically induced soil surface particle velocity (due to sufficient acoustic-to-seismic coupling) have been used in detection schemes. Since the interface between the top plate and the soil responds nonlinearly to pressure fluctuations, characteristics of landmines, the soil, and the interface are rich in nonlinear physics and allow for a method of buried landmine detection not previously exploited. Tuning curve experiments (revealing "softening" and a back-bone curve linear in particle velocity amplitude versus frequency) help characterize the nonlinear resonant behavior of the soil-landmine oscillator. The results appear to exhibit the characteristics of nonlinear mesoscopic elastic behavior, which is explored. When two primary waves f1 and f2 drive the soil over the mine near resonance, a rich spectrum of nonlinearly generated tones is measured with a geophone on the surface over the buried landmine in agreement with Donskoy [SPIE Proc. 3392, 221-217 (1998); 3710, 239-246 (1999)]. In profiling, particular nonlinear tonals can improve the contrast ratio compared to using either primary tone in the spectrum.

Nonlinear acoustic techniques for landmine detection: Tuning curves and two-tone tests

Measurements of the top surface vibration of a buried (inert) VS 2.2 anti-tank plastic landmine reveal significant resonances in the frequency range between 80 and 650 Hz. Resonances from measurements of the normal component of the acoustically induced soil surface particle velocity (due to sufficient acoustic-to-seismic coupling) have been used in detection schemes. Since the interface between the top plate and the soil responds to pressure fluctuations nonlinearly, characteristics of landmines, the soil, and the interface are rich in nonlinear physics and allow for new methods of buried landmine detection not previously exploited. Tuning curve experiments (revealing ‘‘softening’’ and a back-bone curve linear in particle velocity amplitude versus frequency) help characterize the nonlinear resonant behavior of the soil-landmine oscillator. When two primary waves f1 and f2 drive the soil over the mine, a rich spectrum of nonlinearly generated tones is measured with a geophone on the surface over the buried landmine in agreement with Donskoy [Proc. SPIE 3392 (1998); 3710, 239–246 (1999)]. In profiling, particular nonlinear tonals can improve the contrast ratio compared to using either primary tone in the spectrum. [Work supported by the United States Army Communications-Electronics Command Night Vision and Electronic Sensors Directorate.]

IAEA activities for the production and utilization of isotopes: Some examples of recent work

The paper gives a brief overview of typical IAEA activities which contribute to the production of isotopes in nuclear reactors and accelerators, as well as their use. The areas touched upon include (1) isotope production in research reactors and accelerators, (2) quality control and quality assurance in radioanalytical measurements, (3) neutron activation analysis, (4) nuclear methods for land mine detection, (5) radiopharmaceuticals and nuclear medicine, (6) isotope techniques of water resource management and (7) soil management and crop nutrition.

Monte Carlo simulations as a feasibility tool for non-metallic land-mine detection by thermal-neutron backscattering

The use of Monte Carlo simulations is presented for modelling a simplified land-mine detector system with thermal neutron backscattering (TNB) analysis based on a 252Cf-neutron source. Different aspects and a variety of external conditions, related to localisation and identification of a buried object have been investigated. In particular, the influence of moisture in a formation has been assessed, as moisture can be a serious interference for hydrogen as an indicator for explosives. The results of sensitivity calculations confirm that land-mine detection methods, based on an analysis of TNB may be applicable in homogeneous formations with low porosity provided that pore-water remains <5% by weight. In dry limestone, the TNT-based explosives can be well distinguished from other hydrogen-rich materials, except wood. However, in dry siliciclastic sands TNT explosives and wood are distinguishable.

A comparison of decision-level sensor-fusion methods for anti-personnel landmine detection

We present the sensor-fusion results obtained from measurements within the European research project ground explosive ordinance detection (GEODE) system that strives for the realisation of a vehicle-mounted, multi-sensor, anti-personnel landmine-detection system for humanitarian de-mining. The system has three sensor types: a metal detector (MD), an infrared camera (IR), and a ground penetrating radar (GPR). The output of the sensors is processed to produce confidence levels on a grid covering the test-bed. A confidence level expresses a confidence or belief in a landmine detection on a certain position. The grid with confidence levels is the input for the decision-level sensor-fusion and provides a co-registration of the sensors. The applied fusion methods are naive Bayes' approaches, Dempster–Shafer theory, fuzzy probabilities, a rule-based method, and voting techniques. To compare fusion methods and to analyse the capacity of a method to separate landmines from the background on the basis of the output of different sensors, we provide an analysis of the different methods by viewing them as discriminant functions in the sensor confidence space. The results of experiments on real sensor data are evaluated with the leave-one-out method.

Detection of landmines (Review Paper)

Detection of landmines is a problem concerning both military and peacekeeping forces. This paper reviews literature on strategic minefield layouts, modern mine clearing, and mine countermeasure techniques based on mechanical methods. Discusses hydraulic and signal processing techniques, ion-trap mobility spectrometer, subsurface probing radar and few other novel methods employed for this purpose. The specialised directions that the landmine detection methods are taking are clearly pointed out.

Surface-enhanced raman detection of 2,4-dinitrotoluene impurity vapor as a marker to locate landmines.

Time, cost, and casualties associated with demining efforts underscore the need for improved detection techniques. Reduction in the number of false positives by directly detecting the explosive material, rather than casing material, is desirable. The desired field sensor must, at a minimum, demonstrate reproducibility, the necessary level of sensitivity, portability, instrumental stability, and fast system response times. Ideally, vibrational spectroscopic techniques have the potential to remove false positives, since every chemical has a unique bond structure. Herein, we demonstrate the capabilities of surface-enhanced Raman spectroscopy to detect the chemical vapor signature emanating from buried TNT-based landmines. We present reproducible results obtained from blind tests controlled by the Defense Advanced Research Projects Agency (DARPA) that demonstrate vapor detection of 2,4-dinitrotoluene at concentration levels of 5 ppb or less. The results presented used acquisition times of 30 s on a fieldable system and showed that SERS can be a significant improvement over current landmine detection methods.

Effects of neutron source selection on land-mine detection efficiency

One proposed method of land-mine detection is based on measurements of the 10.8 MeV photons from the 14N(n, γ) reaction. In this study, simulations of the photon production efficiencies for nitrogenous explosive material (TNT), buried in soil having variable moisture content, were completed for different published neutron spectra. Monte Carlo simulations were performed with MCNP with a cylindrical geometry of TNT considered as target material and with neutron energies ranging from thermal to 20 MeV. The numbers of 14N(n, γ) reactions in TNT were tallied to obtain response functions. To find the effectiveness of different neutron sources, response functions were folded with the neutron spectra. Response curves reveal that higher water content increases response for fast neutrons, and reduces response for slow neutrons. Lower energy neutron sources, i.e. D(d, n) or 252Cf, are more suitable than higher energy neutron sources such as 241Am–Be or T(d, n). Although its advantages disappear with increasing depth, the usage of moderating spheres of CH 2 increases the signal significantly when compared with a bare source, while also reducing neutron dose to workers.