Homeland Security, Medical, Pharmaceutical and Non-destructive Testing Applications of Terahertz Radiation

Transcription

1 Applications of THz Radiation APS March Meeting, March 23, 2005 Homeland Security, Medical, Pharmaceutical and Non-destructive Testing Applications of Terahertz Radiation Colin Baker

2 Overview Introduction to terahertz Techniques imaging and spectroscopy Applications of terahertz light Medical Non-destructive testing Pharmaceutical Security Conclusions

3 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

4 TeraView s TPI range

5 What is Terahertz? X Ray Visible Terahertz gap Infrared Millimetre Ultraviolet Microwave and Radio Hz Hz Hz Hz Hz Hz Hz Hz Hz Hz Terahertz region 300 GHz 10 THz (1 mm 30 micron) Until recently inaccessible due to lack of sources and detectors Key properties: Penetrates clothing, leather, paper, plastics, packing materials Materials identification using characteristic Terahertz spectra 3-D imaging capability Non-ionizing - no damage to body or cells

6 Photoconductive THz generation V bias GaAs device 90 fs NIR laser pulse Emitted THz pulse

7 Photoconductive THz detection I GaAs device 90 fs NIR laser pulse THz pulse

8 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.

9 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

10 Medical Imaging Patient 9 (TPP 285) Applications Skin cancer imaging basal cell carcinoma Surgeon s aid tissue typing Endoscopy prostrate & other cancers Status y (mm) Results very promising TPI Scan imager in use for clinical research Probe based systems under development x (mm) 1.00

11 Skin Cancer In vivo surface and depth information

12 Pharmaceuticals 5 Applications absorption Crystalline form 1 1.6THz 1.3THz 1THz 1.8THz absorption Crystalline form 2 1.2THz Process improvement Polymorph screening Tablet inspection Status Reflection imaging system Partnership with Bruker Range of products available including reflection and transmission spectrometers frequency / THz frequency / THz

13 TPI spectra 1000

14 10000 FFT frequency / THz THz electric field / arb. units reference sample signal / arb. units crystalline phonon bands reference sample water vapour lines optical delay / ps wavenumber / cm -1 Terahertz Pulse Profile

15 Form I Form II Form III Form IV Form V Absorbance (decadic) Frequency/THz mg, 13mm diameter tablet 20% sulphathiazole in PE Wavenumber/cm -1 Samples provided by Terry Threlfall, U. of Southampton

16 Using terahertz pulsed imaging as a tool to investigate coating integrities single incident THz pulse multiple return pulses Reflected THz pulses probe coating structure coated tablet

17 Non-destructive mapping of coating thickness in pharmaceutical tablets Terahertz pulses reflect from each coating layer Time of flight and scanning over surface allows mapping of coating layers

18 Security z z z z z Checkpoint people screening for hidden weapons & explosives Stand-off detection of explosives Baggage screening for explosives Screening for biological & chemical agents white powder detection

19 Terahertz & Security: Key Issues Signatures Do threat materials have characteristic signatures? Are they distinct from confusion materials? Barriers Will terahertz penetrate clothing and other barriers? Reflection Can signatures be detected in reflection? Distance Can we see (at least) 10 metres? Source power/ detector sensitivity Atmospheric absorption Systems Can we design practical systems? What sources and architectures should we use?

20 Terahertz spectra of explosives Absorption (offset for clarity) Semtex PE4 RDX PETN HMX TNT Terahertz transmission spectra Energetic compounds and explosives All show characteristic features at terahertz frequencies Note: Most features above 0.5 THz Barrier material absorption limits practical range to 3THz Frequency (THz) Kemp et. al., Proc SPIE 5070, 44 (2003)

21 Semtex-H reference measurements Absorption and reflection spectra of Semtex calculated from measurements in transmission spectrometer Reflectance Absorption Reflectance Frequency/THz Absorption/cm -1 TeraView data November 2004

22 Measurements of potential confusion materials Absorbance (decadic) 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 co-codamol (+3.0) milk chocolate Frequency (THz) Absorbance (decadic) Cocoa Washing Powder Aspirin Milk Chocolate Flour Ibuprofen Blusher Paracetamol Soap Sugar Vitamins Tribe et. al., Proc SPIE 5354, 168 (2004) Frequency/THz

23 Clothing & Barrier Materials Absorbance (decadic) Cotton Silk Wool Leather Nylon Polyester Polyester/cotton All clothing materials are partially transparent Absorption increases with frequency Limits useful frequency range to 2-3 THz Frequency/THz Tribe et. al., Proc SPIE 5354, 168 (2004)

24 Detecting metals, non-metals and explosives hidden in clothing terahertz beam wool 2 layers cotton 4 layers hidden object subject s arm

25 Detecting metals, non-metals and explosives hidden in clothing image metal scalpel blade ceramic plastic sheet explosive 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

26 TeraView data March 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

27 Ongoing development programmes Objective: move from proof-of-principle to prototype and then to fieldable system Two projects: People Screening Hand Wand Stand-off Explosives Detection

28 People Screening Wand Terahertz wand to detect metal & non-metallic weapons and explosives Marketing partnership with Smiths Detection Initial prototype under construction Detection techniques and algorithms being developed Smiths Detection

29 Terahertz reflection spectrum from Hand Wand raw data TeraView data January 2005

30 Stand-off Explosives Detection 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

31 Experimental system Femtosecond pulsed laser Beamsplitter Delay stage Target Detector Emitter

32 Experimental System in Operation Response of stand-off THz system Target 1m Path Length over 2m Power Frequency/THz

33 Water windows correspond to spectral features of explosives Semtex RDX Water absorption Frequency (THz)

34 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 THz 0.08 Reflectance Semtex-H System Purged Semtex-H Calculated Frequency/THz TeraView data November 2004

35 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 Reflectance Semtex-H at 1m (no purging) Semtex-H Calculated Frequency/THz TeraView data November 2004

36 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 Reflectance Semtex-H at 1m (no purging), after data processing Calculated Frequency/THz TeraView data November 2004

37 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 Reflectance 0.08 SX-2 Semtex-H Calculated Semtex-H Frequency/THz TeraView data November 2004

38 Conclusion Terahertz is very promising technology for many applications Reflectance Semtex-H at 1m (no purging), after data processing Calculated Frequency/THz Proof-of-principle confirmed with measurements and data Technology now moving forward to commercialisation

39 Acknowledgements Dr Bill Tribe Dr Tom Lo Dr Mike Kemp Dr Philip Taday Michael Withers Michael Evans Dr Bryan Cole Dr Ian Bradley Dr Simon Chandler