As part of security research, this main research aim addresses integrative systems for the detection of harmful and hazardous substances on surfaces or in the air. In contrast to the research and development work on the long range effect of continuous laser radiation, pulsed high power lasers are used for this application.
In the Institute of Technical Physics, there is experience in long range detection of gaseous substances. Examples of this are the remote detection of methane gas in the surroundings of a possible leakage in a natural gas pipeline (CHARM) or the detection of water vapour concentration in the atmosphere (WALES). For the standoff detection it is primarily the determination and recognition of unexpected substances that represents a challenge in the detection and identification methods. Owing to the multitude of possible hazardous substances, a combination of different measurement processes is to be used for an early and reliable detection of potential states of risk. For a thorough description of the situation, different kinds of contact free and discreet standoff detection diagnostics are considered and their practicality is assessed: LIDAR (light detection and ranging), DIAL (differential absorption), LIF (laser induced fluorescence), Raman spectroscopy and also LIBS (laser induced breakdown spectroscopy) especially for applications of surfaces contaminations. All processes take advantage of the fact that laser light is dispersed, absorbed or re-emitted by matter. The returning radiation is picked up using a telescope and investigated with respect to its intensity, polarisation, and spectral distribution. By comparison to existing databases any existing hazardous substances can then be classified or even identified.
As part of the first validation investigations on the laser test range, gold in the high nanogram range could be detected using the LIBS method on surfaces at a distance of 50 m. To demonstrate LIBS capability for detection of explosives, black powder was used as a first representative. It consists of a mixture of sulphur, charcoal, and potassium nitrate (KNO3). The plasma emission of pure KNO3 shows a characteristic doublet at 692 nm, which is used for black powder identification. Thereby, black powder can be detected at distances as far as 135 m using pulsed laser radiation of 500 mJ at a wavelength of 1064 nm for plasma generation.