TERAHERTZ IMAGING and DETECTION OF SUICIDE BOMBERS*

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TERAHERTZ IMAGING and DETECTION OF SUICIDE
BOMBERS

• J. F. Federici, D. Gary, B. Schulkin, F. Huang,
  H. Altan Department of Physics
• R. Barat Department of Chemical Engineering
• K. Walsh
• Picatinny Arsenal

Federici_at_adm.njit.edu http//physics.njit.edu/fed
erici
Funded by US Army and NSF
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Outline

• THz Basics
• Basics of Interferometric Imaging
• Spectral Information
• Spatial information
• Simulated Images
• cm resolution at 100m distances
• Spectral Resolution of Explosives and Metals
• Analysis of Images
• Current and Future Work

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What is Terahertz (THz)?
Visible
Radio Microwave T-rays Infrared
UV X-rays
108 109 1010 1011 1012 1013
1014 1015 1016 1017
Frequency (Hz)
1 THz frequency 300 ?m wavelength or 33 cm-1 or
4.1 meV or T 48 K
Also known as Far-Infrared or sub-millimeter
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THz at NJIT

• 1997-2001 Developed various THz sources,
  detectors, and imaging techniques
• Two PhD students graduated, 9 publications in
  THz technology
• 2000-2001 Developed concept for Detection of
  explosives, chemical and biological weapons using
  new THz imaging methodology.
• Spring 2001 - Proposal for cargo screening
  submitted to FAA
• Post 9/11 - National Science Foundation and US
  Army Funding
• 8 publications since 2002, 2 patents pending

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Wide Area Surveillance

• NJIT Team is developing THz imaging techniques
  for Stand-Off Detection of concealed Explosives,
  Chemical/Biological Agents
• Development of Technique/ Hardware for Imaging
• Development of Image Analysis

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Comparison with Other Techniques

• X-Ray, Neutron Scattering - Uses high energy
  radiation
• damages biological systems - eg. damages DNA/
  tissues
• permissible exposure limited - more difficult
  for use on people.
• THz - low energy radiation - non-ionizing
• no damage to biological tissue
• differentiation of target compounds based on THz
  color
• Imaging and color information combination will
  reduce false alarm rate.

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Disadvantages of THz for Scanning for Explosives
/ BioAgents

• Metals are opaque to THz
• will reflect the THz
• THz strongly absorbed by water
• will not detect explosives inside the body
• THz scanners will likely be used in conjunction
  with other detection techniques.
• Not a forensic technique - looking for 1cm2 size
  blocks of material

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Application of High-Resolution X-Ray Raman
Scattering to Homeland SecurityT. A. Tyson, Q.
Qian (NJIT), Z. Zhong, C.-C. Kao and W. Caliebe
(NSLS)
X-ray absorption spectroscopy of is one
method that can be used to identify chemical
systems by threshold spectra. The resonance
features in x-ray absorption spectra are uniquely
related with the molecular structure enabling
rapid chemical identification. Utilizing
100 KeV x-rays with high penetration power and a
transmission x-ray analyzer system based on a
working design (left), we will develop a system
for detecting explosives and chemical weapons by
fingerprinting their spectra.
The upper and lower left panels show the full
spectrometer and blow up of the analyzer array,
respectively. Each of the nine x-ray focusing
mirrors can be independently aligned with micro
radian precision in the horizontal and vertical
planes. The lower left panel show the carbon
K-edge spectrum of graphite measured in energy
loss mode (x-ray Raman spectrum) with a
resolution of 0.5 eV.
Tyson_at_adm.njit.edu
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Advantages of THz for Scanning for Explosives /
Bio and Chemical Agents

• THz transmits through most non-metallic
  materials plastic, paper , clothing
• THz yields transmission / reflection spectra of
  targets

Explosives Kemp (2003)
Transmissive Bas.Sub. Spectra Woolard et al (2003)
See papers from Proc. SPIE 5070, (2003)
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Interferometric Imaging - Motivation

• A THz digital camera would be ideal for THz
  imaging
• However
• consumer digital cameras ? imaging arrays of
  1024 by 768 pixels or 780,000 individual detector
  elements in the array.
• That high density of detectors in THz range not
  technologically possible.

• Therefore
• To image in the THz, one must generate images
  using only a few to a few hundred detector
  elements.
• Possible Solution Interferometric imaging

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Sample Array Geometry
Detector Distance to Origin
Exponential Distances Ensure Non-redundant
Spacing of Detector Pairs
66 detector pair combinations Rotation of 90o
with data acquired every 1o 6690 5940 points
in u-v plane
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Estimated Angular Resolution
Field-of-View determined by either Field-of-View
of individual Detectors or Bandwidth of Detectors.
Angular (Spatial) Resolution determined by
spacing between Detector Pairs.
A 1m baseline array has a spatial resolution of
3cm at 100m! Scaling down to cargo unit or
hand-held ? size of smoke detector!
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Simulation of THz Imaging Array
Detection of RDX and Metal at a distance of 30m
RDX
Metal
Objects 1.5cm in size
Composite Image combination of THz images taken
at 5 different frequencies ? Spectral and Spatial
Images
Objects with spectral content of RDX colored
Red Objects reflecting all THz radiation colored
white
Sidelobes
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Focusing of Image
Focal Length
Object
ImagingArray
Single frequency, uncleaned image
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Image Analysis - Neural Networks
THz Image at 1 frequency
Neural Network Analysis
BLUE metal coin PINK bioagent GREEN
flour ORANGE starch
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Present and Future Work

• Development of Benchtop model underway to
  demonstrate key technological components
• Detect C4 versus peanut butter hidden in
  clothing.
• Scale up to imaging system for suicide bombers
  (system size about 1m)
• Scale to hand-held/ cargo container unit (10cm
  size, battery operated unit)