Applications of THz Radiation – APS March Meeting, March 23, 2005
Homeland Security, Medical, Pharmaceutical and Non-destructive Testing Applications of Terahertz Radiation
Colin Baker
[email protected] [email protected] Overview
z Introduction to terahertz z Techniques – imaging and spectroscopy z Applications of terahertz light Medical Non-destructive testing Pharmaceutical Security z Conclusions TeraView The Terahertz Company
• Founded April 2001 Cambridge, England • Exclusive focus on terahertz technology and applications – 30+ staff • Close relationship with Cavendish Laboratory, Cambridge University • Developed world’s first portable terahertz imager & spectrometer • Focus markets medical imaging, pharmaceuticals, security screening, non-destructive testing TeraView’s TPI range What is Terahertz?
Micro- Ultra- Infra- Terahertz Milli- wave and X Ray violet Visible metre red gap Radio
1019Hz 1018Hz 1017Hz 1016Hz 1015Hz 1014Hz 1013Hz 1012Hz 1011Hz 1010Hz
• Terahertz region 300 GHz – 10 THz (1 mm – 30 micron) • Until recently – inaccessible due to lack of sources and detectors • Key properties: z Penetrates clothing, leather, paper, plastics, packing materials
z Materials identification using characteristic Terahertz spectra
z 3-D imaging capability
z Non-ionizing - no damage to body or cells Photoconductive THz generation
V bias GaAs device
90 fs NIR laser pulse Emitted THz pulse Photoconductive THz detection
I GaAs device
90 fs NIR laser pulse THz pulse Basics of THz Pulsed Imaging
• TPI provides for time of flight analysis, as well as producing spectral information.
• A proportion of the incident pulse will be reflected back whenever there is a change in the refractive index.
• Reconstruction of the multiple detected pulses permits depth profiling. X-Y raster scanning builds a 3D image. Non-Destructive Testing – 3-D Terahertz Imaging of integrated circuit package
visible images
Terahertz images – seeing inside the chip
top surface 1mm deep 2 mm deep Medical Imaging
Patient 9 (TPP 285)
0 z Applications
Skin cancer imaging – basal 0.20 cell carcinoma 0.40 Surgeon’s aid – tissue typing
Endoscopy – prostrate & 0.60
other cancers y (mm) z Status 0.80
Results very promising 1.00 TPI Scan imager in use for x (mm) clinical research
Probe based systems under development Skin Cancer In vivo surface and depth information Pharmaceuticals
5
4 4 Crystalline1.8THz Crystalline 3 form 1 form 2 1.6THz 3 tion ption p 2 1.3THz z Applications 1.2THz 1THz 2 absor absor 1 1
Process improvement 0 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 frequency / THz Polymorph screening frequency / THz
Tablet inspection z Status
Reflection imaging system
Partnership with Bruker
Range of products available including reflection and transmission spectrometers TPI spectra 1000 freFFTquency / THz 0.81.52.33.03.84.5 10000 108
7 reference 10 8000 reference sample s it sample 106 un . 6000 water vapour s 5
arb 10 lines d / unit l e i 4 f 4000 10 arb. ic r al / 103
elect 2000 sign z
H 2
T 10 crystalline 0 101 phonon bands
-2000 100 0 5 10 15 20 25 30 35 25 50 75 100 125 150 optical delay / ps wavenumber / cm-1
Terahertz Pulse Profile Frequency/THz Form I 0.6 1.2 1.8 2.4 Form II Form III 7 Form IV Form V 6
5
4
3 sorbance (decadic) b 2 A
1
0 400mg, 13mm diameter tablet 20 40 60 80 20% sulphathiazole in PE Wavenumber/cm-1
Samples provided by Terry Threlfall, U. of Southampton Using terahertz pulsed imaging as a tool to investigate coating integrities
single incident THz pulse
coated tablet multiple return pulses Reflected THz pulses probe coating structure Non-destructive mapping of coating thickness in pharmaceutical tablets
z Terahertz pulses reflect from each coating layer z Time of flight and scanning over surface allows mapping of coating layers Security
z Checkpoint people screening for hidden weapons & explosives z Stand-off detection of explosives z Baggage screening for explosives z Screening for biological & chemical agents z ‘white powder’ detection Terahertz & Security: Key Issues z Signatures
Do threat materials have characteristic signatures?
Are they distinct from confusion materials? z Barriers
Will terahertz penetrate clothing and other barriers? z Reflection
Can signatures be detected in reflection? z Distance
Can we see (at least) 10 metres?
Source power/ detector sensitivity
Atmospheric absorption z Systems
Can we design practical systems?
What sources and architectures should we use? Terahertz spectra of explosives
Terahertz transmission spectra Semtex Energetic compounds and PE4 explosives All show characteristic features RDX at terahertz frequencies Note: PETN Most features above 0.5 THz HMX Barrier material absorption TNT limits practical range to 3THz Absorption (offset for clarity) Absorption (offset
01234 Frequency (THz)
Kemp et. al., Proc SPIE 5070, 44 (2003) Semtex-H reference measurements
Absorption and reflection spectra of Semtex calculated from measurements in transmission spectrometer
0.12 Reflectance 60 0.10 Absorption 50 -1 0.08 40 nce /cm a 0.06 30 on
0.04 20 rpti Reflect 10
0.02 Abso 0 0.00 0.50 0.75 1.00 1.25 1.50 1.75 2.00 Frequency/THz
TeraView data November 2004 Measurements of potential confusion materials • TeraView has measured a library of terahertz spectra of common materials - developed with support of UK Department of Trade & Industry • Also includes many pharmaceutical compounds
• No significant confusion found between explosives and harmless materials 4 Cocoa Washing Powder Aspirin 5 Milk Chocolate co-codamol 3 Flour ) c
ic) Ibuprofen i (+3.0) 4 d Blusher Paracetamol ecad eca d ( 3 Soap
(d 2 Sugar ce
Vitamins milk ce 2 n chocolate Absorban
1 sorba 1 Ab 0 01234 Frequency (THz) 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0
Tribe et. al., Proc SPIE 5354, 168 (2004) Frequency/THz Clothing & Barrier Materials
4 Cotton Silk z All clothing materials are Wool Leather partially transparent Nylon 3 Polyester z Absorption increases Polyester/cotton with frequency decadic) 2 z Limits useful frequency range to 2-3 THz bance (
1 Absor
0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Frequency/THz
Tribe et. al., Proc SPIE 5354, 168 (2004) Detecting metals, non-metals and explosives hidden in clothing
terahertz beam
wool – 2 layers
cotton – 4 layers hidden object
subject’s arm Detecting metals, non-metals and explosives hidden in clothing
image
metal ceramic plastic sheet explosive scalpel blade
depth profile
Terahertz images of objects (approx 1cm across) hidden under 2 layers of wool and 4 layers of shirt material
Kemp et al. Proc SPIE 5070, 2003 Terahertz detection of sheet explosive underneath clothing
Image of 1cm square piece of SX2 sheet explosive against skin, hidden under two layers of woollen jumper and four layers of cotton shirt material –
TeraView data March 2003 Ongoing development programmes
z Objective: move from proof-of-principle to prototype … z … and then to fieldable system z Two projects:
People Screening Hand Wand
Stand-off Explosives Detection People Screening Wand
z Terahertz wand to detect metal & non-metallic weapons and explosives z Marketing partnership with Smiths Detection z Initial prototype under construction z Detection techniques and algorithms being developed
Smiths Detection Terahertz reflection spectrum from Hand Wand – raw data
TeraView data January 2005 Stand-off Explosives Detection
z Stand-off Explosives Detection
Programme funded by UK Home Office PSDB, with US participation
Laboratory prototypes under construction
Initial target 1m
Source & detector development to achieve larger stand-off distances
Development of detection techniques and algorithms Experimental system
Beamsplitter Femtosecond pulsed laser
Delay stage
Detector Target
Emitter Experimental System in Operation •Response of stand-off THz system •Target 1m •Path Length over 2m
100 10-1 10-2 10-3 -4 10 Power 10-5 10-6 10-7 10-8 01234 Frequency/THz Water windows correspond to spectral features of explosives
Semtex
RDX
Water absorption
0123 Frequency (THz) Semtex-H Stand-off spectrum at 1 metre
THz spectrum of Semtex-H (composed of RDX and PETN) measured data at stand off distance of 1 m System purged with nitrogen gas to remove water vapour.
Data collected in 70 ms, with a spectral range of 0.3 – 2 THz
0.08 e c 0.06 tan c
Refle 0.04 Semtex-H System Purged Semtex-H Calculated
0.02 0.50 0.75 1.00 1.25 1.50 1.75 2.00 Frequency/THz
TeraView data November 2004 Semtex-H spectrum with water vapour
THz spectrum of Semtex-H measured data at stand off distance of 1m in atmospheric air Note effect of water vapour absorption lines
0.08
nce 0.06
flecta e
R 0.04 Semtex-H at 1m (no purging) Semtex-H Calculated 0.02 0.50 0.75 1.00 1.25 1.50 1.75 2.00 Frequency/THz
TeraView data November 2004 Semtex-H spectrum corrected for water vapour effects Reflection spectrum at stand off distance of 1m, data collected in 70ms Water vapour absorption lines removed by data processing algorithm.
0.08
0.06
Reflectance 0.04 Semtex-H at 1m (no purging), after data processing Calculated 0.02 0.50 0.75 1.00 1.25 1.50 1.75 2.00 Frequency/THz
TeraView data November 2004 Semtex and SX-2 spectra Spectra of two different RDX based explosives showing same distinctive features Data collected at 1m stand-off through normal atmosphere with 70ms integration time – water vapour lines removed
0.08 SX-2 Semtex-H Calculated Semtex-H
0.06 ance
Reflect 0.04
0.02 0.50 0.75 1.00 1.25 1.50 1.75 2.00 Frequency/THz
TeraView data November 2004 Conclusion
Semtex-H at 1m (no purging), after data processing 0.08 Calculated ance t z
Terahertz is very c
e 0.06 l f e promising technology R 0.04 0.50 0.75 1.00 1.25 1.50 1.75 2.00 for many applications Frequency/THz z Proof-of-principle confirmed with measurements and data z Technology now moving forward to commercialisation Acknowledgements
z Dr Bill Tribe z Dr Tom Lo z Dr Mike Kemp z Dr Philip Taday z Michael Withers z Michael Evans z Dr Bryan Cole z Dr Ian Bradley z Dr Simon Chandler