Is it possible to use electromagnetic metal detection methods for non-metallic materials? This was a major question of my Ph.D. thesis, where it formed three of five chapters. In short, it can be done by bumping against the limits of the magneto quasi-static approximation.
Publications
The main description of this work has been shared in the following IEEE TGRS paper:
2017
High-frequency electromagnetic induction sensing of non-metallic materials
John Brevard Sigman, Benjamin Barrowes, Kevin O’Neill, and 4 more authors
IEEE Transactions on Geoscience and Remote Sensing, 2017
With other related publications including:
2017
Initial Development of a High-frequency EMI Sensor for Detection of Subsurface Intermediate Electrically Conductive (IEC) Targets
Janet E Simms, John B Sigman, Benjamin E Barrowes, and 4 more authors
Journal of Environmental and Engineering Geophysics, 2017
2016
Coil design considerations for a high-frequency electromagnetic induction sensing instrument
John B. Sigman, Benjamin E. Barrowes, Yinlin Wang, and 5 more authors
Intermediate electrical conductivity (IEC) materials (101S/m < σ < 104S/m), such as carbon fiber (CF), have recently been used to make smart bombs. In addition, homemade improvised explosive devices (IED) can be produced with low conducting materials (10-4S/m < σ < 1S/m), such as Ammonium Nitrate (AN). To collect unexploded ordnance (UXO) from military training ranges and thwart deadly IEDs, the US military has urgent need for technology capable of detection and identification of subsurface IEC objects. Recent analytical and numerical studies have showed that these targets exhibit characteristic quadrature response peaks at high induction frequencies (100kHz − 15MHz, the High Frequency Electromagnetic Induction (HFEMI) band), and they are not detectable with traditional ultra wideband (UWB) electromagnetic induction (EMI) metal detectors operating between 100Hz − 100kHz. Using the HFEMI band for induction sensing is not so simple as driving existing instruments at higher frequencies, though. At low frequency, EMI systems use more wire turns in transmit and receive coils to boost signal-to-noise ratios (SNR), but at higher frequencies, the transmitter current has non-uniform distribution along the coil length. These non-uniform currents change the spatial distribution of the primary magnetic field and disturb axial symmetry and thwart established approaches for inferring subsurface metallic object properties. This paper discusses engineering tradeoffs for sensing with a broader band of frequencies ever used for EMI sensing, with particular focus on coil geometries.
2017
A hybrid coil system for high frequency electromagnetic induction sensing
John B. Sigman, Benjamin E. Barrowes, Kevin O’Neill, and 4 more authors
2017
2017
Void and landmine detection using the HFEMI sensor
Benjamin E. Barrowes, Fridon Shubitidze, John B. Sigman, and 4 more authors
2017
2017
Ultra-wideband EMI sensing for subsurface DU detection
Fridon Shubitidze, Benjamin E. Barrowes, John B. Sigman, and 1 more author
2017
2016
Detection of Conductivity Voids and Landmines using High Frequency Electromagnetic Induction
B. E. Barrowes, J. B. Sigman, K. O’Neill, and 4 more authors
2016
2016
Carbon fiber and void detection using high-frequency electromagnetic induction techniques
Benjamin E. Barrowes, John B. Sigman, YinLin Wang, and 5 more authors
Ultrawide band electromagnetic induction (EMI) instruments have been traditionally used to detect high electric conductivity discrete targets such as metal unexploded ordnance. The frequencies used for this EMI regime have typically been less than 100 kHz. To detect intermediate conductivity objects like carbon fiber, even less conductive saturated salts, and even voids embedded in conducting soils, higher frequencies up to the low megahertz range are required in order to capture characteristic responses. To predict EMI phenomena at frequencies up to 15 MHz, we first modeled the response of intermediate conductivity targets using a rigorous, first-principles approach, the Method of Auxiliary Sources. A newly fabricated benchtop high-frequency electromagnetic induction instrument produced EMI data at frequencies up to that same high limit. Modeled and measured characteristic relaxation signatures compare favorably and indicate new sensing possibilities in a variety of scenarios.
2014
High frequency electromagnetic induction sensing for non-metallic ordnances detection
F. Shubitidze, J. Sigman, K. O’Neill, and 2 more authors
High frequency (>100 kHz) electromagnetic induction (HFEMI) sensing phenomena are investigated for nonmetallic ordnances detection and discrimination. HFEMI responses are studied using numerical and experimental data. The numerical modeling is done via the method of auxiliary sources, and data are collected using a new HEMI system, that has been developed at our lab. The comparisons between modeled and actual data are illustrated for a non-metallic 105 mm projectile.
High-frequency electromagnetic induction sensing of non-metallic materialsIEEE Transactions on Geoscience and Remote Sensing, 2017
Initial Development of a High-frequency EMI Sensor for Detection of Subsurface Intermediate Electrically Conductive (IEC) TargetsJournal of Environmental and Engineering Geophysics, 2017
Coil design considerations for a high-frequency electromagnetic induction sensing instrument2016
A hybrid coil system for high frequency electromagnetic induction sensing2017
Void and landmine detection using the HFEMI sensor2017
Ultra-wideband EMI sensing for subsurface DU detection2017
Detection of Conductivity Voids and Landmines using High Frequency Electromagnetic Induction2016
