Jürgen Röpcke

Cohort Profile: The Study of Health in Pomerania

Henry Volzke, y Dietrich Alte,1y Carsten Oliver Schmidt, Dorte Radke, Roberto Lorbeer, Nele Friedrich, Nicole Aumann, Katharina Lau, Michael Piontek, Gabriele Born, Christoph Havemann, Till Ittermann, Sabine Schipf, Robin Haring, Sebastian E Baumeister, Henri Wallaschofski, Matthias Nauck, Stephanie Frick, Andreas Arnold, Michael Junger, Julia Mayerle, Matthias Kraft, Markus M Lerch, Marcus Dorr, Thorsten Reffelmann, Klaus Empen, Stephan B Felix, Anne Obst, Beate Koch, Sven Glaser, Ralf Ewert, Ingo Fietze, Thomas Penzel, Martina Doren, Wolfgang Rathmann, Johannes Haerting, Mario Hannemann, Jurgen Ropcke, Ulf Schminke, Clemens Jurgens, Frank Tost, Rainer Rettig, Jan A Kors, Saskia Ungerer, Katrin Hegenscheid, Jens-Peter Kuhn, Julia Kuhn, Norbert Hosten, Ralf Puls, Jorg Henke, Oliver Gloger, Alexander Teumer, Georg Homuth, Uwe Volker, Christian Schwahn, Birte Holtfreter, Ines Polzer, Thomas Kohlmann, Hans J Grabe, Dieter Rosskopf, Heyo K Kroemer, Thomas Kocher, Reiner Biffar,17,y Ulrich John20y and Wolfgang Hoffmann1y

Quantum Cascade Laser Absorption Spectroscopy as a Plasma Diagnostic Tool: An Overview

The recent availability of thermoelectrically cooled pulsed and continuous wave quantum and inter-band cascade lasers in the mid-infrared spectral region has led to significant improvements and new developments in chemical sensing techniques using in-situ laser absorption spectroscopy for plasma diagnostic purposes. The aim of this article is therefore two-fold: (i) to summarize the challenges which arise in the application of quantum cascade lasers in such environments, and, (ii) to provide an overview of recent spectroscopic results (encompassing cavity enhanced methods) obtained in different kinds of plasma used in both research and industry.

Tunable Diode Laser Diagnostic Studies of H2-Ar-O2 Microwave Plasmas Containing Methane or Methanol

Tunable infrared diode laser absorption spectroscopy has been used to detect the methyl radical and ten stable molecules in H2-Ar-O2microwave plasmas containing up to 7.2% of methane or methanol, under both flowing and static conditions. The degree of dissociation of the hydrocarbons varied between 30 and 90% and the methyl radical concentration was found to be in the range 1010–1012molecules cm−3. The methyl radical concentration and the concentrations of the stable C-2 hydrocarbons C2H2, C2H4, and C2H6, produced in the plasma decayed exponentially when increasing amounts of O2were added at fixed methane or methanol partial pressures. In addition to detecting the hydrocarbon species, the major products CO, CO2, and H2O were also monitored. For the first time, formaldehyde, formic acid, and methane were detected in methanol microwave plasmas, formaldehyde was detected in methane microwave plasmas. Chemical modeling with 57 reactions was used to successfully predict the concentrations in methane plasmas in the absence of oxygen and the trends for the major chemical product species as oxygen was added.

On the hydrocarbon chemistry in a H2 surface wave discharge containing methane

Tunable infrared diode laser absorption spectroscopy has been used to detect the methyl radical and four stable molecules, CH4, C2H2, C2H4 and C2H6, in a H2 surface wave discharge (f = 2.45 GHz and power density ≈10-50 W cm-3) containing up to 10% methane under different flows (Φ = 22-385 sccm) and pressures (p = 0.1-4 Torr). The degree of dissociation of the methane precursor varied between 20% and 85% and the methyl radical concentration was found to be in the range of 1012 molecules cm-3. The methyl radical concentration and the concentrations of the stable C-2 hydrocarbons C2H2, C2H4, C2H6, produced in the plasma, increased with an increasing amount of added CH4 as well as with increasing pressure. For the first time, fragmentation rates of methane (RF(CH4) = 1×1015-2.5×1016 molecules J-1) and conversion rates to the measured C-2 hydrocarbons (RC(C2Hy): 5×1013-3×1015 molecules J-1) could be estimated with dependence on the flow and pressure in a surface wave discharge. The influence of diffusion and convection on the spatial distribution of the hydrocarbon concentration in the discharge tube was considered by a simple model.

Time-Resolved Quantum Cascade Laser Absorption Spectroscopy of Pulsed Plasma Assisted Chemical Vapor Deposition Processes Containing BCl3

In situ measurements are reported giving insight into the plasma chemical conversion of the precursor BCl3 in industrial applications of boriding plasmas. For the online monitoring of its ground state concentration, quantum cascade laser absorption spectroscopy (QCLAS) in the mid-infrared spectral range was applied in a plasma assisted chemical vapor deposition (PACVD) reactor. A compact quantum cascade laser measurement and control system (Q-MACS) was developed to allow a flexible and completely dust-sealed optical coupling to the reactor chamber of an industrial plasma surface modification system. The process under the study was a pulsed DC plasma with periodically injected BCl3 at 200 Pa. A synchronization of the Q-MACS with the process control unit enabled an insight into individual process cycles with a sensitivity of 10-6 cm-1Hz-1/2. Different fragmentation rates of the precursor were found during an individual process cycle. The detected BCl3 concentrations were in the order of 1014 moleculescm-3. The reported results of in situ monitoring with QCLAS demonstrate the potential for effective optimization procedures in industrial PACVD processes.

RES-Q-Trace: A Mobile CEAS-Based Demonstrator for Multi-Component Trace Gas Detection in the MIR

Sensitive trace gas detection plays an important role in current challenges occurring in areas such as industrial process control and environmental monitoring. In particular, for medical breath analysis and for the detection of illegal substances, e.g., drugs and explosives, a selective and sensitive detection of trace gases in real-time is required. We report on a compact and transportable multi-component system (RES-Q-Trace) for molecular trace gas detection based on cavity-enhanced techniques in the mid-infrared (MIR). The RES-Q-Trace system can operate four independent continuous wave quantum or interband cascade lasers each combined with an optical cavity. Twice the method of off-axis cavity-enhanced absorption spectroscopy (OA-CEAS) was used, twice the method of optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS), respectively. Multi-functional software has been implemented (i) for the general system control; (ii) to drive the four different laser sources and (iii) to analyze the detector signals for concentration determination of several molecular species. For the validation of the versatility and the performance of the RES-Q-Trace instrument the species NO, N2O, CH4, C2H4 and C3H6O, with relevance in the fields of breath gas analysis and the detection of explosives have been monitored in the MIR with detection limits at atmospheric pressure in the ppb and ppt range.

3rd International Workshop on Infrared Plasma Spectroscopy

This volume containsd a selection of papers from the third Infrared Plasma Spectroscopy (IPS) Workshop held in Greifswald, Germany in July 2008. Although not all the contributions have been written up in time for the deadline for this volume, nevertheless the 12 contributions presented here give a fair representation of the conference topics. The conference comprised four different types of contribution. Firstly, four invited lectures focussed on the prime areas of interest. Secondly, eight shorter contributed talks, grouped as closely as possible with the appropriate invited lecture. These contributed talks covered topics in both pure and applied infrared plasma spectroscopy. A feature of the two previous IPS conferences has been a contribution from commercial organisations namely those involved in manufacturing devices, detectors and spectrometers. This group of participants formed the third part of the conference programme and gave five oral presentations covering topics like QCL and detector/detection developments and novel spectrometer designs. The fourth contributing group comprised 27 poster presentations. It should be mentioned that some of the latter were poster versions of contributed talks. The conference was remarkable for the wide spread of topics covered in a relatively small meeting, consisting of 44 participants. The participants were made up of 34 scientists from within Europe and 4 from the rest of the world. It is interesting to reflect on changes that have occurred since the previous meeting just a year earlier. Two clear developments which have occurred are the emergence of Quantum Cascade Lasers (QCL) and their use in Cavity Ring Down (CRD) spectroscopy. A major shift from cw lead salt diode lasers to cw and pulsed QCL in both pure and applied projects now seems to be well under way. The topics covered in the earlier conferences focussed more on applying infrared spectroscopy to plasma monitoring and control. When choosing the topics to cover the scientific committee felt that this time it would be useful to emphasise new spectroscopic developments as well as covering applications. This might serve as a guide as to where the subject of infrared spectroscopy in combination with plasma sources might be heading in the future i.e. to emphasize pure infrared spectroscopy developments. The first invited lecture (G Guelachvili and N Picque) and the last invited lecture (F K Tittel, Y Bakhirkin, R Curl, A Kosterev, R Lewicki, D Thomasz and S So) were chosen to set the scene and realise this objective. The second (R Engeln, R Zijlmans, S Welzel, O Gabriel, J-P van Helden, J Ropcke and D Schram) and third (X Aubert, C Lazzaroni, D Marinov, O Guaitella, S Welzel, A Pipa, J Ropcke and A Rousseau) invited talks focussed on the application of the IR laser techniques with particular emphasis on the role of surfaces in plasmas and the relevance of plasma surface interactions. Surface plasma interactions did not feature strongly in the two earlier meetings and so this topic too, along with the emphasis on novel infrared spectroscopy techniques, represents a new direction for the conference. Paul B Davies and Jurgen Ropcke International Scientific Committee P B Davies, Cambridge, UK: Chair J Ropcke, Greifswald, Germany: Co-Chair R Engeln, Eindhoven, Netherlands G Hancock, Oxford, U K M Hori, Nagoya, Japan H Linnartz, Leiden, Netherlands R Martini, New York, USA J Meichsner, Greifswald, Germany A Rousseau, Paris, France Local Organizing Committee J Ropcke (INP: Chair) F Hempel (INP: Secretary) J Meichsner (IfP, University of Greifswald) N Lang (INP) L Glawe (INP) C Krcka (INP) B Lindemann (INP)