homeland security technology council

7/29/2019 Homeland Security Technology Council

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Department of Physics

TERAHERTZ IMAGING and DETECTION OF

SUICIDE BOMBERS*

J. F. Federici, D. Gary, B. Schulkin, F. Huang, H. AltanDepartment of Physics

R. Barat

Department of Chemical Engineering

K. Walsh

Picatinny Arsenal

*Funded by US Army and NSF

[email protected]

http://physics.njit.edu/~federici


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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)?

1 THz frequency = 300 m wavelengthor 33 cm-1 or 4.1 meV or T = 48 K

Radio Microwave T-rays Infrared UV X-rays

Frequency (Hz)

108 109 1010 1011 1012 1013 1014 1015 1016 101

Visible

Also known as Far-Infrared or sub-millimeter


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THz at NJIT

1997-2001 Developed various THz sources, detectors, andimaging 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.

Nota forensic technique - looking for 1cm2

size blocks of material


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Application of High-Resolution X-Ray Raman Scattering to Homeland Security

T. A. Tyson, Q. Qian (NJIT), Z. Zhong, C.-C. Kao and W. Caliebe (NSLS)

X-ray absorption spectroscopy of is onemethod 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 highpenetration 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.

260 280 300 320 340 360

0.75

0.80

0.85

0.90

0.95

1.00

Inten

sity

Energy(eV)

Carbon K-Edge of Graphite (X-Ray Raman)

The upper and lower left panels show the full spectrometerand 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.

[email protected]


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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*

ExplosivesKemp (2003)

Transmissive Bas.Sub. Spectra

Woolard et al (2003)

* See papers fromProc. SPIE5070, (2003)


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Interferometric Imaging - Motivation

Therefore

To image in the THz, one must generate images using only a few to a few

hundred detector elements.

Possible Solution: Interferometric imaging

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.


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Sample Array Geometry

)1(

n

obrad

Detector Distance

to Origin:

Exponential Distances Ensure Non-

redundant Spacing of Detector Pairs

66 detector pair combinationsRotation of 90o with data acquired every 1o:

66*90 = 5940 points in u-v plane


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Estimated Angular Resolution

b (meters)10 1 0.1 0.01 0.001

0.1 62" 10' 1.7o 17o 170o

1.0 6.2" 62" 10' 1.7o 17o

(THz)

10.0 0.6" 6.2" 62" 10' 1.7o

Field-of-View determined by either Field-of-View of individualDetectors 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

Objects 1.5cm in size

Composite Image combination ofTHz 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

RDX Metal

Sidelobes


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Focusing of Image

ImagingArray

Object

Focal Length

Single frequency, uncleaned image


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Image Analysis - Neural Networks

U

A A

A A U

A A A

U A A

U A

F A

S S

A S S

U A A U U A S S

U A A A A U A S F

U U F U

A A A A F F F A A

U S U U S F F F F F F F A

U M M M M M S A A U F F F A

M M M M M M S U U

U M M M M M M U

U M M M M M U

S M M M M U A

A S S U

BLUE = metal coin

PINK= bioagent

GREEN = flour

ORANGE = starch

THz Image at 1 frequency

Neural Network Analysis

U U U U S S

A S S A S S

F A F F A F F

U F F A U F A

A

U U A U

A A U A A A U U A A A A A A A U U A A U

U A A


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Present and Future Work

Development of Benchtop model underway todemonstrate 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)

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