Stand-off Detection at the DLR Laser Test Range Applying Laser-Induced Breakdown Spectroscopy

The DLR laser test range at Lampoldshausen allows for optical measurements under daylight conditions at distances up to 130 m. This infrastructure is very suitable for the development of stand-off detection systems of biological, chemical and explosive hazardous substances. In a first step, laser-induced breakdown spectroscopy (LIBS) has been introduced to this test site. A basic LIBS set-up and first LIBS spectra of selected samples are presented. A Nd:YAG laser beam was focussed by a Cassegrain type telescope onto different samples at distances exceeding 50 m. The light of the generated plasma plume was collected by a Newtonian telescope, and analyzed by a gated broadband CCD-spectrometer system. The Nd:YAG laser yields pulse energies up to 800 mJ at a wavelength of 1064 nm and a pulse width of 8 ns. Optionally the second and third harmonics can be extracted. LIBS spectra from 10 nm layers of gold on a silicon wafer were recorded. In addition, LIBS spectra from black powder were measured, and compared to the spectrum of potassium nitrate, which is a main component of black powder and shows very characteristic emission. LIBS spectra of the above samples have also been acquired with an excitation laser wavelength in the eye-safe region. Recorded spectra are measured as a function of the laser wavelength, pulse energy, and energy density on the target and are compared to the literature

Application of Standoff LIF to Living and Inactivated Bacteria Samples

To minimize the impact of an airborne bio-agent output, sensitive, specific and swift detection and identification are essential. A single method can hardly meet all of these requirements. Point sensors allow highly sensitive and specific identification but are localized and comparatively slow. Most laser-based standoff systems lack selectivity and specificity but provide real-time detection and classification in a wide region with additional information about location and propagation. A combination of both methods allows benefiting from their complementary assets and may be a promising solution to optimize detection and identification of hazardous substances. Here, we present progress for an outdoor bio-detector based on laser-induced fluorescence (LIF) developed at the DLR Lampoldshausen. After excitation at 280 and 355 nm, bacteria species express unique fluorescence spectra. Upon deactivation, the spectral features change depending on the applied method

Standoff laser induced fluorescence of living and inactivated bacteria

Biological hazards, such as bacteria, represent a non-assessable threat in case of an accident or a terroristic attack. Rapid detection and highly sensitive identification of released, suspicious substances at low false alarm rates are challenging requirements which one single technology cannot cope with. It has been shown that standoff detection using laser-induced fluorescence (LIF) can provide information on the class of bioorganic substances in real-time1. In combination with traditional, highly sensitive, but non-standoff methods, the time for identification of the threat can be optimized. This work is aimed at the selectivity of LIF technology for different bacterial strains. A second important aspect examines how to deal with inactivated bacteria and how their fluorescence signature changes after deactivation. LIF spectra of closely and more distantly related bacterial strains are presented as well as spectra of bacteria treated by different inactivation methods

Experimental and numerical analysis of atmospheric propagation of high energy laser

The transmission of high power laser radiation through the atmosphere is influenced by turbulent motion of the air. As a result the beam experiences an alteration regarding its position and its distribution, which increases with increasing propagation length. In order to analyze the atmospheric influence on the laser beam propagation a disk laser with a maximum output power of 6 kW and a wavelength of 1.03 µm is operated on a 130 m long free transmission laser test range in Lampoldshausen. The test range is equipped with a variety of sensors, which continuously monitor the current status of the weather conditions. Power sensors and camera systems at the beginning and the end of the test range measure the laser beam parameters before and after propagation. The experimental results are compared with a numerical analysis of the laser beam propagation performed by the software TALAP (Turbulent Atmosphere and Laser Beam Propagation), developed at the Institute of Technical Physics of DLR. It is based on the Kolmogorov turbulence model, which considers turbulent cells of different scale sizes. First measurements of power transmission, diameter of the laser beam and variations of its center of gravity are performed on a sunny and on a rainy day. The results show a good correlations to the measurements of the turbulence strength and the visibility. A comparison to the numerical analysis has shown coincidences. Future measurements will be performed at different weather conditions and seasons. Experimental results will be used to modify the simulation software, if necessary

Standoff detection and classifcation procedure for bioorganic compounds by hyperspectral laser-induced fluorescence

The high and still increasing number of attacks by hazardous bioorganic materials makes enormous demands on their detection. A very high detection sensitivity and differentiability are essential, as well as a rapid identification with low false alarm rates. One single technology can hardly achieve this. Point sensors can collect and identify materials, but finding an appropriate position is time consuming and involves several risks. Laser based standoff detection, however, can immediately provide information on propagation and compound type of a released hazardous material. The coupling of both methods may illustrate a solution to optimize the acquisition and detection of hazardous substances. At DLR Lampoldshausen, bioorganic substances are measured, based on laser induced fluorescence (LIF), and subsequently classified. In this work, a procedure is presented, which utilizes lots of information (time-dependent spectral data, local information) and predicts the presence of hazardous substances by statistical data analysis. For that purpose, studies are carried out on a free transmission range at a distance of 22 m at two different excitation wavelengths alternating between 280 nm and 355 nm. Time-dependent fluorescence spectra are recorded by a gated intensified CCD camera (iCCD). An automated signal processing allows fast and deterministic data collection and a direct subsequent classification of the detected substances. The variation of the substance parameters (physical state, concentration) is included within this method

Robots in education : an introduction to high-tech social agents, intelligent tutors, and curricular Tools

Robots in Education is an accessible introduction to the use of robotics in formal learning, encompassing pedagogical and psychological theories as well as implementation in curricula. Today, a variety of communities across education are increasingly using robots as general classroom tutors, tools in STEM projects, and subjects of study. This volume explores how the unique physical and social-interactive capabilities of educational robots can generate bonds with students while freeing instructors to focus on their individualized approaches to teaching and learning. Authored by a uniquely interdisciplinary team of scholars, the book covers the basics of robotics and their supporting technologies; attitudes toward and ethical implications of robots in learning; research methods relevant to extending our knowledge of the field; and more

E-Bologna und der Virtual Linguistics Campus

Die vorliegende Arbeit zeigt, dass für eine vernünftige Umsetzung des Bologna-Prozesses die Integration von E-Learning-Elementen, die inhaltlich Innovatives leisten und gleichzeitig die Betreuungsintensität in Lehrveranstaltungen reduzieren, zwingend erforderlich ist. Mit dem Virtual Linguistics Campus, über den seit SS 2003 Online-Inhalte für verschiedene B.A. Studiengänge bereitgestellt werden, wurde seit 2001 konsequent ein Weg gegangen, der den Aufbau und die Realisierung neuer Studiengänge erheblich erleichtert. Daher werden Konzeption und Einsatzgrundlagen der Lernmodule des VLC sowie allgemeine Aspekte der Nachhaltigkeit und Qualitätssicherung vorgestellt. (DIPF/Orig.

Shift Learning Activities – vom Inverted Classroom Mastery Model zum xMOOC

Die Hochschullehre unterzieht sich derzeit einem dramatischen Wandel. Die bisher hörsaalbasierte Phase der Inhaltsvermittlung und -erschließung wird zunehmend digitalisiert und ermöglicht den Studierenden in vielen Fachgebieten ein effizientes Selbststudium. Für die Präsenzphase ergeben sich dadurch je nach Digitalisierungsgrad vielfältige Möglichkeiten: Vom zusätzlichen gemeinsamen Üben bis zum völligen Wegfall. Anhand einer über drei Semester gehenden Langzeitstudie, in der mehrere digitalisierte Lehrveranstaltungen mit Hunderten von Studierenden aus verschiedenen Perspektiven evaluiert wurden, unterstreicht dieser Beitrag nicht nur den Stellenwert einer ‚neuen‘ Präsenzphase, sondern er zeigt auch, wie xMOOCs von diesen neuen digitalen Szenarien profitieren können. (DIPF/Orig.

[Design and Investigation of a Hybrid Optical Resonator for Medium Energy COIL]

High brightness laser radiation of chemical oxygen iodine lasers (COIL) requires resonator types especially adapted to low gain medium and rectangular cavity geometry. For medium energy class lasers, those resonators suffer from small magnification numbers and therefore often imply sophisticated optical concepts. Selected solutions should not inhibit the demands of a field deployment of the laser system. Outside the laboratory additional nonoptical properties like compactness, ruggedness and ease of operation become important. Resonators that enable reliable operation under field conditions should be composed of a reasonable number of optical components and a straightforward architecture. Based on the amplification characteristics of a 10 kW-class COIL, off-axis hybrid resonator configurations are designed and pre-evaluated theoretically. The most promising candidates are technically realized and applied to the DLR-COIL device. The resonators are tested for their alignment sensitivity and brightness parameters. Positive branch and negative branch hybrid resonators are discussed. Particularly, the negative branch hybrid resonator meets the above challenges. A further promising design approach, the multi-pass hybrid resonator, will be depicted within this paper