Example of measured backgrounds and signals

In Figure 6.5, three different spectra measured with the biolidar are shown. These are for clean air (only Raman return), and the simulants Ovalbumin (egg white, a simulant for toxins) and Bacillus Thuringensis (Turex, a nonpathogenic simulant for Bacillus Antracis, Anthrax). A more in-depth description of the trial during which there measurements were made are found in a separate report [22].

28 FFI-rapport 2008/02025

0

350 400 450 500 550 600 650 700 OA BT Air

Signal (arb units)

Wavelength (nm)

Figure 6.5 Measured biolidar returns for air, and with aerosol releases of Ovalbumin (OA) and Bacillus Thuringensis (BT)

In Figure 6.6, a typical signal on the PMT is shown for a release at ~200 m distance. The peak at 100 m distance and later drop is the return signal from the naturally occurring aerosols in the air.

The reason for this to decrease at shorter distances than 100 m is that the telescope in this experiment was focused on ~250 m, and that elastic scatter at much shorter distances is not effectively collected by the optics. In the trial, a 500 m line of sight ended in a tree line. The ICCD camera was gated to avoid the fluorescence from the trees.

0

Figure 6.6 PMT signal during aerosol release at 200 m distance. The curve is explained in the text

7 Conclusions

In conclusion, the FFI biolidar has been described and the choice of components has been

explained, as well as potential challenges, like operation under high ambient light conditions. The lidar uses ultraviolet laser light to induce fluorescence in aerosols with biological content, and a spectrally resolved receiver stage to measure the fluorescence spectrum. Initial testing was

FFI-rapport 2008/02025 29

performed in a field trial and demonstrated that detection of biological aerosols is possible even at daylight conditions.

The lidar was tested in a field trial in Umeå in Sweden in Novenber 2006 [22]. One of the reasons for going abroad for such test is the lack of necessary facilities in Norway. This initial trial showed that the lidar was capable of detecting biological aerosols at a distance. During this trial and subsequent work, a list of improvements to be made to the lidar was developed. This is listed in [22].

In the design of the lidar, it was chosen to keep the elements simple and – if possible – with better performance than expected necessary. This way it will be possible to reduce the performance of the lidar gradually to get an estimate of the performance needed in a final design. For example, the spectrograph and ICCD camera is clearly capable of a higher spectra resolution than

necessary, but was chosen over a PMT-array with less spectral channels to be able to investigate how the number of spectral channels affects the performance of the lidar. The 355 nm laser was chosen over a 266 nm alternative because of higher available output energies and also that standard telescopes and lenses can be used to collect the 400-600 nm fluorescence following 355 nm excitation, while the shorter wavelengths emitted with 266 nm excitation require special coated mirrors and nonstandard lenses. The required spectral resolution will be subject to further study with the biolidar, and future upgrades may also include 266 nm excitation.

References

[1] Proceedings from. In: 7th Joint Conference on Standoff Detection for Chemical and Biological Defence, (Joint Science and Technology Office, USA, 2006).

[2] Proceedings from. In: 6th Joint Conference on Standoff Detection for Chemical and Biological Defence, (Joint Science and Technology Office, USA, 2004).

[3] Chemical Biological Radiological Nuclear and Explosives (CBRNE) Sensing IX. A W Fountain, ed, Proceeding of SPIE, SPIE, Bellingham, WA, USA, vol 6954, 2008.

[4] Spectroscopy, Encyclopædia Britannica. http://search.eb.com/eb/article-80635 [5] R M Measures. Laser remote sensing - fundamentals and applications. Krieger

publishing company, Malabar, Florida, 1992.

[6] M Sletmoen. Vekselvirkning mellom lys og biologisk materiale. FFI/Notat 2008-00828 (In Norwegian), FFI, Kjeller, 2008. www.ffi.no

[7] D B Wetlaufer. Ultraviolet Spectra of Proteins and Amino Acids. Advances in Protein Chemistry, 17: 303-390, 1962.

[8] A T Timperman, K E Oldenburg, and J V Sweedler. Native fluorescence detection and spectral differentiation of peptides containing trypophan and tyrosine in capillary electrophoresis. Analytical Chemistry, 67: 3421-3426, 1995.

30 FFI-rapport 2008/02025

[9] S Pakalnis, V Sitas, H Schneckenburger, and R Rotomskis. Picosecond absorption spectroscopy of biologically active pigments NADH, FMN and fluorescence marker Rhodamine-123. In: The Third Internet Photochemistry and Photobiology Conference, J Photochem. Photobiol. B: Biology, (www.photobiology.com/photobiology2000, 2000).

[10] J R Simard, G Roy, P Mathieu, V Larochelle, J McFee, and J Ho. Standoff integrated bioaerosol active hyperspectral detection (SINBAHD): Final report. DRDC Valcartier TR 2002-125, DRDC, Valcartier, Quebec, 2003.

[11] J R Simard, G Roy, P Mathieu, V Larochelle, J McFee, and J Ho. Standoff sensing of bioaerosols using intensified range-gated spectral analysis of laser-induced

fluorescence. Ieee Transactions on Geoscience and Remote Sensing, 42: 865-874, 2004.

[12] Zemax, 7.5, Bellevue, WA: Zemax development corporation, 2008. www.zemax.com [13] S Nicolas. Optical design for a biological lidar system. FFI/Notat (to be published),

FFI, Kjeller, 2008. www.ffi.no

[14] S Solberg, NILU, Kjeller. Personal communication. 2005

[15] MODTRAN, 4, Hanscom AFB, MA: Air Force Research Labs, 2008.

[16] G W Faris, R A Copeland, K Mortelmans, and B V Bronk. Spectrally resolved absolute fluorescence cross sections for Bacillus spores. Applied Optics, 36: 958-967, 1997.

[17] J R Stevens. Measurements of the ultraviolet fluorescence cross sections and spectra for bacillus anthracis simulants. ECBC-CR-004, Edgewood CBC, Aberdeen Proving Ground, MD, 1999.

[18] V Sivaprakasam, A L Huston, C Scotto, and J D Eversole. Multiple UV wavelength excitation and fluorescence of bioaerosols. Optics Express, 12: 4457-4466, 2004.

[19] J Kunnil, S Sarasanandarajah, E Chacko, and L Reinisch. Fluorescence quantum efficiency of dry Bacillus globigii spores. Optics Express, 13: 8969-8979, 2005.

[20] J R Schott. Remote sensing: the image chain approach. 2nd ed., Oxford University Press, New York, 2007.

[21] Andor Technology, Belfast, www.andor.com

[22] Ø Farsund and G Rustad. Standoff detection of biologic aerosols by means of UV-laser induced fluorescence - results from Umeå trial. FFI-rapport 2008/01990, FFI, Kjeller, 2008. www.ffi.no

[23] FieldSpecPro Full Range User's Guide, rev C. Analytical Spectral Devices Inc, Boulder, CO, 2002. www.asdi.com

[24] IEC 60825-1 Safety of laser products - Part 1: Equipment classification and requirements, Geneva: International Electrotechnical Commission, 2007.

[25] C Duncan, Andor Technology, Belfast. Personal communication. 2007

FFI-rapport 2008/02025 31