Torbjörn Tjärnhage

Development of a fluorescence-based point detector for biological sensing

This paper presents the status of an ongoing development of a point detector for biological warfare agent sensing based on ultraviolet laser-induced fluorescence from single particles in air. The detector will measure the fluorescence spectra of single particles in a sheath flow air beam. The spectral detection part of the system consists of a grating and a photomultiplier tube array with 32 channels, which measure fluorescence spectra in the wavelength band from 300 nm to 650 nm. The detector is designed to measure laser induced fluorescence from single laser pulses and has been tested by measuring fluorescence from simulants of biological warfare agents in aqueous solution. The solutions were excited with laser pulses at the wavelengths of 293 nm and 337 nm. The paper also presents preliminary results on the sheath flow particle injector and time-resolved measurements of fluorescence from biological warfare agent simulants in solution.

Evaluation of biological aerosol stand-off detection at a field trial

We have performed a field trial to evaluate technologies for stand-off detection of biological aerosols, both in daytime and at night. Several lidar (light detection and ranging) systems were tested in parallel. We present the results from three different lidar systems; one system for detection and localization of aerosol clouds using elastic backscattering at 1.57 μm, and two systems for detection and classification of aerosol using spectral detection of ultraviolet laser-induced fluorescence (UV LIF) excited at 355 nm. The UV lidar systems were utilizing different technologies for the spectral detection, a photomultiplier tube (PMT) array and an intensified charge-coupled device (ICCD), respectively. During the first week of the field trial, the lidar systems were measuring towards a semi-closed chamber at a distance of 230 m. The chamber was built from two docked standard 20-feet containers with air curtains in the short sides to contain the aerosol inside the chamber. Aerosol was generated inside the semi-closed chamber and monitored by reference equipments, e.g. slit sampler and particle counters. Signatures from several biological warfare agent simulants and interferents were measured at different aerosol concentrations. During the second week the aerosol was released in the air and the reference equipments were located in the centre of the test site. The lidar systems were measuring towards the test site centre at distances of either 230 m or approximately 1 km. In this paper we are presenting results and some preliminary signal processing for discrimination between different types of simulants and interference aerosols.

Bioaerosol detection technologies

Preface (Per Jonsson, Goran Olofsson and Torbjorn Tjarnhage) Section 1 (Introduction to Bioaerosol Detection) 1. Introduction and Bioaerosol Detection Terminology (Torbjorn Tjarnhage, Per Jonsson, and Yannick Morel) 2. History of the Early Biodetection Development (Jim Ho) 3. Physical and Biological Properties of Bioaerosols (Jakob Londahl) 4. Dispersion in the Atmosphere (Lennart Thanning and Leif Persson) 5. Aerosol Sampling and Transport (Jorma Keskinen and Marko Marjamaki) Section 2 (Principles and Technologies for Bioaerosol Detection) 6. Light Scattering and Particle Charge Techniques for the Detection of Biological Warfare Agents (James M. Clark) 7. Bioaerosol Detection with Fluorescence Spectroscopy (Per Jonsson and Fredrik Kullander) 8. Bioaerosol Detection with Atomic Emission Spectroscopy (Nicolas Leone, Damien Descroix and Abdelsalam Mohammed) 9. Mass Spectrometry Techniques in the Analysis of Bioaerosols: Development and Advancement (Rabih E. Jabbour and A. Peter Snyder) 10. Detection of Bioaerosol by Raman Spectroscopy (Hilsamar Felix-Rivera and Samuel P. Hernandez-Rivera) 11. Biological Detection with Terahertz Spectrocopy (Tatiana Globus and Boris Gelmont) Section 3 (Standoff Sensor Systems for Bioaerosol Detection) 12. Introduction to Stand-off Detection of Biological Warfare Agents (Per Jonsson and Goran Olofsson) 13. Spectrally Resolved Laser-Induced Fluorescence Lidar Based Standoff Biodetection System (Jean-Robert Simard, Sylvie Buteau and Pierre Lahaie) 14. Standoff Aerosol Size Determination Based on Multiple Field-of-View Elastic Scattering (Gilles Roy and Nathalie Roy) Section 4 (Outlook and Challenges) 15. Trends in Biological Detection (Per Jonsson and Torbjorn Tjarnhage)

Spectral detection of ultraviolet laser induced fluorescence from individual bioaerosol particles

We present results of a measurement system designed for detecting the fluorescence spectrum of individual aerosol particles of biological warfare agents excited with laser pulses at wavelengths around 290 or 340 nm. The biological aerosol is prepared and directed into a narrow air beam. A red laser is focused on the aerosol beam and a trigger photomultiplier tube monitor the presence of individual particles by measuring the scattered light. When a particle is present in the detection volume, a laser pulse is triggered from an ultraviolet laser and the fluorescence spectrum is acquired with a spectrometer based on a diffraction grating and a 32 channels photomultiplier tube array with single-photon sensitivity. The spectrometer measures the fluorescence spectra in the wavelength region from 300 to 800 nm. In the experiment we used different simulants of biological warfare agents. These bioaerosol particles were excited by a commercial available gas laser (337 nm), or a laser (290 nm) that we have developed based on an optical parametric oscillator with intracavity sum-frequency mixing. In the analysis of the experiments we compare the measured signals (fluorescence spectra, total fluorescence energy and the scattered energy) from the individual bioaerosol particles excited with the two different ultraviolet wavelengths.

Detection and monitoring of CWA and BWA using LIBS

Results related to laser induced breakdown spectroscopy (LIBS) as an analytical tool for applications regarding CWA and BWA detection/monitoring will be presented and discussed in this paper. A ‘real-time’ aerosol analysis set-up using LIBS on single μm-sized particles (sampled from ambient air into a particle stream) has been developed and evaluated. Here, a two-stage triggering unit ensures a high hit-rate of the sampled aerosol particles and the optical emission from the laser induced plasma is collected and coupled into an echelle spectrometer equipped with an intensified CCD detector. Each CCD image (echellogram), optimally originating from a single μm-sized particle, is then analyzed and the result treated by an alarm algorithm built from a database using multivariate data analysis. The database signatures of simulant agents and interferents were obtained in controlled atmospheres (aerosol chamber/wind tunnel) as well as from measurements in different ambient background. The LIBS bioaerosol system with alarm algorithm was also tested in ‘real-life’ settings (subway station) during simulant dispersions. Painted surfaces have also been analyzed by LIBS to obtain information about residues of organophosphates on, or within, the paint. Depth analysis has been performed, which illustrated the possibility to monitor diffusion and penetration behavior of neat CWAs and simulant chemicals in the paint layer by following the intensity of phosphorous emission lines in single shot LIBS spectra as function of number of laser pulses. In addition, LIBS analysis was also performed after simple ethanol decontamination procedures, after which P emission lines still could be observed. The possibilities and challenges associated with the different set-ups and applications will be briefly discussed in connection with the presented results.

Trends in Biological Detection

This chapter shortly summarizes some highlights from the development of modern biodetectors and looks forward in what directions the development is going. The initial expectations may have settled to a more realistic level and biodetectors are now finding their role in different military and security applications. Also biodetectors originally developed for military or security applications are being used in different environmental, medical, industrial and pure scientific applications. Comparison of different detector characteristics and their functioning in a certain application have become more important and methods to test and evaluate biodetectors are now under harmonization and standardization.

Introduction and Bioaerosol Detection Terminology

This chapter is a brief introduction to the biodetection field and provides a conceptual understanding of the capability of the current biodetection technologies. As many biodetector technologies have their origin in military applications, a very brief discussion about biological weapons is also included. Finally, the chapter addresses basic definitions and nomenclature that are used in the biodetection community.