Sensor Fusion for the Detection of Landmines

The detection of buried anti-personnel mines (APMs) is widely considered as a problem which may only be solved with a combination of two or more complementary sensors. We present processing and fusion results obtained from a multisensor data set, acquired with a pulse induction metal detector (MD), a pulsed ultra wide band ground penetrating radar (GPR) and a 3–5 thermal infra-red (IR) camera. Various types of soils, clutter objects and burial conditions were recorded. Anti-personnel mines included minimum metal mines as well as mines with a significant metal content. We use a special projection to map a 3D GPR data cube, with time or depth as vertical co-ordinate, into a horizontal plane view 2D image. Object contours are then derived, based on an edge extraction method, followed by an automatic detection of circular shapes with a Hough-transform. In the association step, the stand-off IR image, the metal detector and GPR images and related detections are mapped onto a common cartesian grid on the ground surface. Detection results are fused on a decision level, using a Bayesian approach. Our results indicate that the GPR performance approximately matches that of the metal detector. With both sensors all metallic mines and around 60% of the minimum metal mines were detected. In the case of two false alarms per square meter combined detection probability clearly exceeds single sensor performance.     

The Feasibility of Neutron Moderation Imaging for Land Mine Detection

Neutron moderation land mine detection involves irradiating the ground with fast neutrons and subsequently detecting the thermalized neutrons which return. This technique has been studied since the 1950s, but only using non-imaging detectors. Without imaging, natural variations in moisture content, surface irregularities, and sensor height variations produce sufficient false alarms to render the method impractical in all but the driest conditions. This paper describes research to design and build a prototype land mine detector based on neutron moderation imaging. After reviewing various neutron detector technologies, a design concept was developed. It consists of a novel thermal neutron imaging system, a unique neutron source to uniformly irradiate the underlying ground, and hardware and software for image generation and enhancement. A proof-of-principle imager has been built, but with a point source offset from the detector to roughly approximate a very weak uniform source at the detector plane. Imagery from the detector of mine surrogates is presented. Realistic Monte Carlo simulations were performed using the same two dimensional neutron imaging geometry as the detector in order to assess its performance. The target-to-background contrast was calculated for various soil types and moisture contents, explosive types and sizes, burial depths, detector standoffs, and ground height variations. The simulations showed that the neutron moderation imager is feasible as a land mine detector in a slow scanning or confirmation role and that image quality should be sufficient to significantly improve detector performance and reduce false alarm rates compared to non-imaging albedo detection, particularly in moist soils, where surface irregularities exist and when the sensor height is uncertain. Performance capability, including spatial resolution and detection times, was estimated.     

A Multi-channel System for Qualitative Explosive and Drug Detection

It is well known that under blue LED/laser illumination a class of synthetic conjugated polymers can create fluorescence, and after absorbing a certain class of explosive vapors the fluorescence will be quenched thus the explosives can be detected. The unsolved problems are how can we detect drug, TATP and nitro aromatic explosives with the same device, how can we distinguish different explosives and drugs, and how can we avoid false alarms; solving these problems are crucial for world security. We have developed a new synthetic conjugated polymer with single molecule layer and coated on porous silicon with large surface area to increase quenching signal at least one order, based on this new film a small handheld explosive detector with sensitivities of 0.1 pg for TNT and 0.1 ng for black gun powder are obtained. Many explosives and drugs (such as TNT, RDX, PETN, black gun powder, cocaine, etc.) have been tested, from their quenching curves and our data base we are able to distinguish them qualitatively and avoid false alarms. Therefore we believe our detector can be used not only for battle field but also for airports, government entrances and other security check points. Last year, after face to face competition, our device was selected as the only security detector for the G20 summit held in Hangzhou, China. Here, we will give our detailed designs to let readers develop detectors by themselves to counter terrorism in the world and save lives.     

New Neutron, Gamma and X-Ray Detectors

New detectors intended to record absorbed doses of neutron, gamma and X-radiation in a range of 0–1500 Mrad are described. One of these detectors is based on dibutylphthalate (DP), another is based on epoxy resin, and a 5-40 detector is a mixture of dibutylphthalate and epoxy resin. Experimental methods of detector calibration and for the interpretation of measured absorbed doses are given for these detectors. All three detectors cover a measured dose range of 0–30000 Mrad. The measurement accuracy is ±10% and, in fact, does not depend on the radiation dose rate within 20–2000 rad/s at temperatures of 20–80°C. The detectors can be applied in the atomic industry, radiation biotechnology, medicine (for object radicidation), the food industry for radiation handling of foodstuffs, radiation processing of paper (for example, mail radiation processing), etc.     

Effect of dissimilar metals on fretting fatigue behavior of Ti–6Al–4V

An investigation was conducted to explore fretting fatigue behavior of Ti–6Al–4V specimens in contact with pads of varying composition. Four conditions were selected to provide a range of compositions: Ti–6Al–4V (with two surface finishes), aluminum and nickel. Behavior against each pad condition was evaluated for two pad geometries (cylinder-on-flat, blended flat-on-flat) in two separate test fixtures. Experiments were conducted with varying applied fatigue stresses and contact forces. Applied clamping stresses for the flat-on-flat pads were 200 and 650 MPa. For the cylinder-on-flat geometry, forces were selected to provide Hertzian peak pressures of 292 and 441 MPa. The coefficient of friction, μ, was quantified and pad surfaces were characterized through hardness and composition evaluation. Finite element analyses of the test fixtures were conducted to assess variations in the stress fields.     

A Vacuum Photoemission Detector for X-ray Tomography on the ITER Facility

A vacuum photoemission detector designed for plasma tomography in X rays on the ITER facility is described. Such detectors allow X rays to be detected in the presence of intense neutron and -photon fluxes. The results of tests of a prototype of this detector on a ⁶⁰Co source of rays, its calibration using radiation from an X-ray tube, and tests of its serviceability on the T-10 facility are presented. The values of the valid signal and the signal-to-noise ratio are assessed for the parameters of the ITER facility. Selecting the number of detectors and their arrangement on the ITER facility to ensure the required spatial resolution of the diagnostics is considered.     

A method for measuring spectral and time characteristics of mixed pulsed gamma-neutron fields with scintillation and Cherenkov detectors with nanosecond time resolution

A method for measuring spectral and time characteristics of pulsed mixed (n, γ) fields is described. The essence of this method is that a sequence of signals from individual (n, γ) particles registered by (n, γ) detectors is written in a computer with the subsequent amplitude-time analysis of the signal parameters. Fast scintillation and Cherenkov detectors with FWHM of pulses of ～1.5 and 2.5 ns, respectively, are used as (n, γ) detectors. A TDS-3054 broadband digital oscilloscope records signals and transmits them to the computer through a GPIB-USB interface. The equipment used ensures efficient detection of (n, γ) particles at detector counting rates of up to ～2 × 10⁸ pulses/s. The efficiency of this method has been tested in measurements of characteristics of (n, γ) radiation fields from an ИНГ-031 pulsed neutron generator and from a copper target irradiated with a beam of carbon nuclei with an energy of 200 MeV/amu from the TVN-ITEF acceleration-storage complex.     

32 bin near-infrared time-multiplexing detector with attojoule single-shot energy resolution

We present two implementations of photon counting time-multiplexing detectors for near-infrared wavelengths, based on Peltier cooled InGaAs/InP avalanche photodiodes. A first implementation is motivated by practical considerations using only commercially available components. It features 16 bins, pulse repetition rates of up to 22 kHz, and a large range of applicable pulse widths of up to 100 ns. A second implementation is based on rapid gating detectors, permitting dead times below 10 ns. This allows one to realize a high dynamic-range 32 bin detector, able to process pulse repetition rates of up to 6 MHz for pulse widths of up to 200 ps. Analysis of the detector response at 16.5% detection efficiency reveals a single-shot energy resolution on the attojoule level.     

Determining the Characteristics of Cosmic-Radiation Nuclei in the Sileye Experiment on Board the Mir Orbital Station

An algorithm for reconstructing the characteristics (charge, mass, and energy) of cosmic-radiation nuclei with 20- to 200-MeV/nucleon energies is described. The detector is a telescope of three two-coordinate planes with two 1-mm-thick iron filters inserted between them. Each plane is composed of two strip silicon detectors with 3.6-mm-wide orthogonally oriented strips, an effective area of 6 × 6 cm², and a thickness of 380 m. The algorithm for reconstructing the nuclei characteristics is based on the analysis of how the specific ionization losses change as the nuclei pass through the filter material. The results of the Monte Carlo simulation are presented for the energy dependence of the telescope acceptance and the energy deposited in the detectors by different nuclei in view of the detector calibration on the nuclear beams of the accelerator. The mass resolution of the telescope is 30, 12, and 5% for He, N, and Al nuclei, respectively. The energy resolution, which is 20%, is much the same for all nuclei.     

A Direct-Charging Detector for Measuring the Pulse Shape, Absorbed Dose Rate, and γ-Radiation Dose

A method for the calculation and the results of experimental tests of direct-charging detectors of -radiation are described. The current sensitivities to monochromatic -rays with energies of 0.3–10 MeV for three plane detector designs with the thicknesses of the dielectric layers of 0.5 to 2 cm are presented. The sensitivity is a function of energy within this range, and its minimum and maximum values differ by a factor of ten. Therefore, when using direct-charging detectors for measuring the absorbed dose rate and radiation dose, the knowledge of the -radiation spectrum is necessary. The spectrum is unnecessary in radiation pulse-shape measurements. The detector amplitude characteristic is linear for values of the absorbed dose rate of 10¹⁵ rad/s.     

An Improved Sensitive Nonselective Radiofrequency Detector for Gas Chromatography

SUMMARY

A dielectric-constant-response radiofrequency detector for gas chromatography is described. The detector is extremely sensitive to organic vapors; it should display general response to compounds which have a dielectric constant different than the carrier gas. Limits of detection have been significantly decreased when compared to previously suggested designs for radio-frequency detectors. The detector is physically small and readily compatible with commercially available chromatographs. A theory for the signal response of the detector is proposed.     

Microtribological analysis of gold and copper contacts

There are millions of electrical contacts subject to relative motion: connectors, relays, chips in cards, switches… Friction and wear in this kind of devices are still a source of concern. Even more, recent developments in MEMS RF switches make compulsory a further understanding of tribological processes in order to get higher operating life (10¹¹ cycles). In this work two commonly used electrical conductors are characterized and compared: copper and gold. Both materials have been deposited by PVD sputtering on silicon wafers and plano-convex lenses. Surfaces were characterized by AFM and roughnesses around 1 nm are obtained. Tribological testing with normal loads in the range 1–20 mN have been carried out. Gold presents quite a constant friction (0.20) over a wide range of relative humidity values. However, copper presents lower friction (0.10) at 33% RH and higher friction when humidity is increased. Contact angle measurements have been performed on both surfaces (Au and Cu) using two different liquids: water (polar) and diiodomethane (non-polar). Surface energy and interfacial energy calculations show that energy in the gold–water interface (23 mN/m) doubles that of copper–water interface. Capillary forces play a key role generating friction in these contacts and water absorption capability of both materials determine their frictional properties in the analyzed range of relative humidity.     

Prototype of a Neutron Detector Based on a Boron-Containing Plastic Scintillator

The characteristics and structural features of a prototype neutron detector based on an -331 boron-containing molded scintillator manufactured at the Institute for High-Energy Physics are described. Owing to the use of this scintillator, the neutron detector is capable of operating at high counting rates with a relatively low level of background events. The detectors developed are applicable to neutron flux measurements in extensive air showers.     

Characterization of nanoscale recording mark on Ge2Sb2Te5 film

We have fabricated nanoscale recording marks on Ge₂Sb₂Te₅ (GST) films with conductive atomic force microscope (AFM). GST films were deposited on glass or polyimide film with thickness of 150–200 nm by the rf–sputtering method. Through current–voltage (I–V) spectroscopy, good cantilevers for fabrication and characterization of nanoscale marks on GST were selected. A fresh and highly conductive tip showed voltage-switching characteristic in the I–V curve, where the threshold voltage was 1.6 V. Nanoscale dot and wire arrays of crystalline phases were successfully obtained by varying sample bias voltage from −10 to 10 V. With highly conductive tips, nanowires having full-width at half-maximum of 20 nm could be fabricated, whereas nanowires could not be fabricated with bias voltage below −2 V. The width of the nanoscale mark was increased by repetition of AFM lithography even with same applied voltage and lithography speed. For a thicker nanowire, the width measured in current-image (C-image) was observed to be 2 times of that measured in topography-image (T-image). This result supports that current sensing provides an image of phase-changed GST area with higher resolution than topography sensing.     

Studying the pulse responses of semiconductor detectors at the SPIN-2 accelerator

Responses of ДППД1, ДППД2, and ДАД1 semiconductor dosimetric detectors to a subnanosecond pulse of the SPIN-2 accelerator were investigated. The pulse response of the register channel was investigated using an И1–12 voltage drop generator with a rise time of 0.05 ns. The duration of the pulse responses of the register channel was estimated to be t _1/2 = 0.19 ns and that of an RTO1044 oscilloscope was t _1/2 = 0.17 ns. The duration of the response of the electron detector with the running wave to the SPIN-2 pulse was t _1/2 = 0.22 ns. The response durations of the ДППД1 and ДППД2 detectors to X-ray pulses were 0.80 and 0.55 ns, respectively. The response durations of ДАД1 diamond detectors were in the range of 0.28–0.40 ns. The restored ДАД1 pulse responses were 0.15–0.30 ns.     

光学遥感图像中复杂海背景下的舰船检测

本文针对光学遥感图像中复杂海背景下的舰船检测问题,提出一种快速精确的舰船检测方法。首先,基于最大对称环绕显著性检测完成初始目标候选区域提取,并结合一种基于元胞自动机的同步更新机制,利用图像局部相似性和舰船目标几何特征,对初始目标候选区域进行更新,并通过OTSU算法获取最终目标候选区域;然后,根据舰船目标的固有特性对方向梯度直方图特征进行改进,提出一种新的表征舰船特性的边缘-方向梯度直方图特征对舰船目标进行描述,与传统HOG特征相比,这种特征向量侧重于对边缘特征的描述,对梯度向量鲁棒性更强,并且仅为一个24维的特征向量,计算复杂度低;最后,通过构建的训练库完成AdaBoost分类器的训练,并利用训练完成后的AdaBoost分类器完成目标的最终判别确认。本文的检测算法,针对尺寸为1 024pixel×1 024pixel的遥感图像,检测时间为2.386 0s,召回率为97.4%,检测精度为97.2%。实验表明,本文提出算法的检测性能优于目前主流的舰船检测算法,在检测时间和检测精度上都能够满足实际工程需要。     

降低CT条盒包装机条盒纸存在检测误检率

针对CT条盒包装机因条盒纸短边上翘而误检停机问题,通过在通道的盖板两边加装校正压板,使条盒纸的上翘得到校正,从而降低了停机频次。     

A systematic investigation of the charging effect in scanning electron microscopy for metal nanostructures on insulating substrates

Scanning electron microscopy is perhaps the most important method for investigating and characterizing nanostructures. A well‐known challenge in scanning electron microscopy is the investigation of insulating materials. As insulating materials do not provide a path to ground they accumulate charge, evident as image drift and image distortions. In previous work, we have seen that sample charging in arrays of metal nanoparticles on glass substrates leads to a shrinkage effect, resulting in a measurement error in the nanoparticle dimension of up to 15% at 10 kV and a probe current of 80 ± 10 pA. In order to investigate this effect in detail, we have fabricated metal nanostructures on insulating borosilicate glass using electron beam lithography. Electron beam lithography allows us to tailor the design of our metal nanostructures and the area coverage. The measurements are carried out using two commonly available secondary electron detectors in scanning electron microscopes, namely, an InLens‐ and an Everhart–Thornley detector. We identify and discriminate several contributions to the effect by varying microscope settings, including the size of the aperture, the beam current, the working distance and the acceleration voltage. We image metal nanostructures of various sizes and geometries, investigating the influence of scan‐direction of the electron beam and secondary electron detector used for imaging. The relative measurement error, which we measure as high as 20% for some settings, is found to depend on the acceleration voltage and the type of secondary electron detector used for imaging. In particular, the Everhart–Thornley detectors lower sensitivity to SE₁ electrons increase the magnitude of the shrinkage of up to 10% relative to the InLens measurements. Finally, a method for estimating charge balance in insulating samples is presented.     

Investigating the characteristics of scintillation detectors for the NEVOD-EAS experiment

A cluster type NEVOD-EAS setup is being constructed by the National Research Nuclear University MEPhI on the basis of the Unique Scientific Facility “Experimental Complex NEVOD”. The NEVODEAS setup is intended for the detection of extensive air showers (EASs) with energies in the region of the knee in the energy spectrum of primary cosmic rays (10¹⁵–10¹⁷ eV). The key elements of the setup are 192 particle detectors for EAS electron–photon and muon components. These detectors are composed of NE102A organic scintillators and Philips XP3462 photomultiplier tubes enclosed in pyramidal steel cases. The techniques used to investigate the characteristics of scintillator plates, photomultiplier tubes, and NEVOD-EAS detectors, as well as the results of this investigation, are discussed. All measurements have been taken using special testing facilities and the precision URAGAN muon hodoscope, with which it is possible to comprehensively investigate the nonuniformity of light collection in the detector (the dependence of the detector response on the location of the passage of a charged particle through its operating volume).     

A Portable γ-Spectrometer Based on a Segmented HPGe Detector with Background Suppression

The results of the development and research of the characteristics of a portable -spectrometer based on a segmented high-purity Ge detector with background suppression and a detection efficiency of 60% are presented. In comparison to the conventional detection of radiation, when the entire detector volume is enabled, the relative improvement of the peak-to-Compton ratio for energies of 662 and 136 keV amounts to a factor of 1.4 and above 1.5, respectively.