Showing papers by "Frank Leipold published in 2011"
TL;DR: The collective Thomson scattering (CTS) diagnostic proposed for ITER is designed to measure projected 1D fast-ion velocity distribution functions at several spatial locations simultaneously as discussed by the authors, where the frequency shift of scattered radiation and the scattering geometry place fast ions that caused the collective scattering in well defined regions in velocity space, here dubbed interrogation regions.
Abstract: The collective Thomson scattering (CTS) diagnostic proposed for ITER is designed to measure projected 1D fast-ion velocity distribution functions at several spatial locations simultaneously. The frequency shift of scattered radiation and the scattering geometry place fast ions that caused the collective scattering in well-defined regions in velocity space, here dubbed interrogation regions. Since the CTS instrument measures entire spectra of scattered radiation, many different interrogation regions are probed simultaneously. We here give analytic expressions for weight functions describing the interrogation regions, and we show typical interrogation regions of the proposed ITER CTS system. The backscattering system with receivers on the low-field side is sensitive to fast ions with pitch |p| = |v∥/v| 0.6–0.8. Additionally, we use weight functions to reconstruct 2D fast-ion distribution functions, given two projected 1D velocity distribution functions from simulated simultaneous measurements with the back- and forward scattering systems.
87 citations
TL;DR: One hour of ozonisation was found to be optimal for the use of washed and unwashed wheat straw for ethanol production (maximum ethanol yield, 52%).
Abstract: The potential of wheat straw for ethanol production after pretreatment with O3 generated in a plasma at atmospheric pressure and room temperature followed by fermentation was investigated. We found that cellulose and hemicellulose remained unaltered after ozonisation and a subsequent washing step, while lignin was degraded up to 95% by O3. The loss of biomass after washing could be explained by the amount of lignin degraded. The washing water of pretreated samples (0–7 h) was analyzed for potential fermentation inhibitors. Approximately 30 lignin degradation products and a number of simple carboxylic acids and phenolic compounds were found, e.g., vanillic acid, acetic acid, and formic acid. Some components had the highest concentration at the beginning of the ozonisation process (0.5, 1 h), e.g., 4-hydroxybenzladehyde, while the concentration of others increased during the entire pretreatment (0–7 h), e.g., oxalic acid and acetovanillon. Interestingly, washing had no effect on the ethanol production with pretreatment times up to 1 h. Washing improved the glucose availability with pretreatment times of more than 2 h. One hour of ozonisation was found to be optimal for the use of washed and unwashed wheat straw for ethanol production (maximum ethanol yield, 52%). O3 cost estimations were made for the production of ethanol at standard conditions.
67 citations
TL;DR: In this article, the sawtooth oscillations interact strongly with the fast-ion population in a wide range of plasma parameters, and the redistribution of fast ions from deuterium NBI in the plasma centre is found to vary throughout velocity space.
Abstract: Experimental investigations of sawteeth interaction with fast ions measured by collective Thomson scattering on TEXTOR are presented. Time-resolved measurements of localized 1D fast-ion distribution functions allow us to study fast-ion dynamics during several sawtooth cycles. Sawtooth oscillations interact strongly with the fast-ion population in a wide range of plasma parameters. Part of the ion phase space density oscillates out of phase with the sawtooth oscillation during hydrogen neutral beam injection (NBI). These oscillations most likely originate from fast hydrogen ions with energies close to the full injection energy. At lower energies passing fast ions in the plasma centre are strongly redistributed at the time of sawtooth collapse but no redistribution of trapped fast ions is observed. The redistribution of fast ions from deuterium NBI in the plasma centre is found to vary throughout velocity space. The reduction is most pronounced for passing ions. We find no evidence of inverted sawteeth outside the sawtooth inversion surface in the fast-ion distribution function.
47 citations
TL;DR: The developed methodology offered the advantage of a simple and relatively fast (0.5–2 h) pretreatment allowing a dry matter concentration of 45–60%.
Abstract: O3 generated in a plasma at atmospheric pressure and room temperature, fed with dried air (or oxygen-enriched dried air), has been used for the degradation of lignin in wheat straw to optimize the enzymatic hydrolysis and to get more fermentable sugars. A fixed bed reactor was used combined with a CO2 detector and an online technique for O3 measurement in the fed and exhaust gas allowing continuous measurement of the consumption of O3. This rendered it possible for us to determine the progress of the pretreatment in real time (online analysis). The process time can be adjusted to produce wheat straw with desired lignin content because of the online analysis. The O3 consumption of wheat straw and its polymeric components, i.e., cellulose, hemicellulose, and lignin, as well as a mixture of these, dry as well as with 50% water, were studied. Furthermore, the process parameters dry matter content and milled particle size (the extent to which the wheat straw was milled) were investigated and optimized. The developed methodology offered the advantage of a simple and relatively fast (0.5–2 h) pretreatment allowing a dry matter concentration of 45–60%. FTIR measurements did not suggest any structural effects on cellulose and hemicellulose by the O3 treatment. The cost and the energy consumption for lignin degradation of 100 g of wheat straw were calculated.
46 citations
TL;DR: Measurements of collective Thomson scattering spectra with clear signatures of ion Bernstein waves and ion cyclotron motion in tokamak plasmas demonstrate that CTS can be used as a fuel ion ratio diagnostic in burning fusion plasma devices.
Abstract: In this Letter we report measurements of collective Thomson scattering (CTS) spectra with clear signatures of ion Bernstein waves and ion cyclotron motion in tokamak plasmas. The measured spectra are in accordance with theoretical predictions and show clear sensitivity to variation in the density ratio of the main ion species in the plasma. Measurements with this novel diagnostic demonstrate that CTS can be used as a fuel ion ratio diagnostic in burning fusion plasma devices.
44 citations
TL;DR: In this article, the decontamination of objects (food) in a sealed container by means of atmospheric pressure plasmas is investigated, and the target is Listeria monocytogenes, a bacterium which causes listeriosis and can be found in plants and food.
41 citations
TL;DR: In this article, a glass fiber reinforced polyester (GFRP) plate was treated using an atmospheric pressure gliding arc with and without ultrasonic irradiation to study adhesion improvement.
Abstract: A gliding arc is a plasma generated between diverging electrodes and extended by a high speed gas flow. It can be operated in air at atmospheric pressure. It potentially enables selective chemical processing with high productivity, and is useful for adhesion improvement of material surfaces. The efficiency of such a plasma treatment at atmospheric pressure can be further improved by ultrasonic irradiation onto the surface during the treatment. In the present work glass fiber reinforced polyester (GFRP) plates are treated using an atmospheric pressure gliding arc with and without ultrasonic irradiation to study adhesion improvement. The airflow at the arc ignition directed the GFRP surface at a grazing angle of approximately 30°. The ultrasonic waves of the frequency range between 20 and 40 kHz were introduced vertically to the GFRP surface through a cylindrical waveguide. It is found that ultrasonic irradiation reduced the OH rotational temperature of the gliding arc. The wettability of the GFRP surface was significantly improved by the plasma treatment without ultrasonic irradiation, and tended to improve furthermore at higher power to the plasma. Ultrasonic irradiation during the plasma treatment consistently improved the wettability. It is seen that polar functional groups were introduced at the surface by the gliding arc treatment, and that the treatment efficiency was enhanced by the ultrasonic irradiation, indicating that the adhesive property would be improved. TOF-SIMS ion images indicate that oxygen and nitrogen are uniformly attached at the treated surfaces with and without ultrasonic irradiation. The principal effect of the ultrasonic irradiation is attributed to enhanced oxidation during the plasma treatment.
35 citations
TL;DR: In this article, a comparison of collective Thomson scattering (CTS) measurements with steady-state Monte Carlo simulations performed with the ASCOT and VENUS codes is presented. But the discrepancy between measurement and simulations for the more parallel projection direction cannot be explained solely by uncertainties in plasma parameters.
Abstract: Here we demonstrate a comprehensive comparison of collective Thomson scattering (CTS) measurements with steady-state Monte Carlo simulations performed with the ASCOT and VENUS codes. The measurements were taken at a location on the magnetic axis as well as at an off-axis location, using two projection directions at each location. The simulations agree with the measurements on-axis, but for the off-axis geometries discrepancies are observed for both projection directions. For the near perpendicular projection direction with respect to the magnetic field, the discrepancies between measurement and simulations can be explained by uncertainty in plasma parameters. However, the discrepancies between measurement and simulations for the more parallel projection direction cannot be explained solely by uncertainties in plasma parameters. Here anomalous fast ion transport is a possible explanation for the discrepancy.
35 citations
TL;DR: In this article, a glass-fibre-reinforced polyester (GFRP) plate was treated with dielectric barrier discharge (DBD) at atmospheric pressure in air for adhesion improvement.
Abstract: A glass-fibre-reinforced polyester (GFRP) plate was treated with dielectric barrier discharge (DBD) at atmospheric pressure in air for adhesion improvement. The effects of ultrasonic irradiation using a high-power gas-jet generator during the treatment were investigated. The optical emission spectrum of the discharge remained almost unchanged by the ultrasonic irradiation, indicating that the bulk property of the discharge was not significantly influenced by the ultrasound. However, the ultrasonic irradiation during the plasma treatment suppressed occasional arcing in the DBD, preventing damage of the GFRP plates. The polar component of the surface energy of the polyester plate was 21 mJ/m2 before the treatment, increased markedly to 52 mJ/m2 after 2-s plasma treatment without ultrasonic irradiation, and further increased slightly after longer treatments. In addition, the polar component of the surface energy increased due to the simultaneous ultrasonic irradiation, indicating that the adhesive property w...
16 citations
TL;DR: In this article, the ozone production was investigated using an atmospheric pressure dielectric barrier discharge in pure O2 at room temperature with and without ultrasonic irradiation at a frequency of either 15 kHz or ∼40 kHz.
Abstract: Ozone production has been investigated using an atmospheric pressure dielectric barrier discharge in pure O2 at room temperature with and without ultrasonic irradiation. It was driven at a frequency of either 15 kHz or ∼40 kHz. The ozone production was highly dependent on the O2 flow rate and the discharge power. Furthermore, powerful ultrasonic irradiation at a fundamental frequency of ∼30 kHz with the sound pressure level of ∼150 dB into the discharge can improve the ozone production efficiency, particularly when operated at the frequency of 15 kHz at the flow rate of 15 L/min.
15 citations
TL;DR: In this paper, a millimeter-wave notch filter with 105 GHz center frequency, >20 GHz passband coverage, and 1-GHz rejection bandwidth has been constructed based on a fundamental rectangular waveguide with cylindrical cavities coupled by narrow iris gaps, i.e., small elongated holes of negligible thickness.
Abstract: Abstract A millimeter-wave notch filter with 105-GHz center frequency, >20-GHz passband coverage, and 1-GHz rejection bandwidth has been constructed. The design is based on a fundamental rectangular waveguide with cylindrical cavities coupled by narrow iris gaps, i.e., small elongated holes of negligible thickness. We use numerical simulations to study the sensitivity of the notch filter performance to changes in geometry and in material conductivity within a bandwidth of ±10 GHz. The constructed filter is tested successfully using a vector network analyzer monitoring a total bandwidth of 20 GHz. The typical insertion loss in the passband is <1.5 dB, and the attenuation in the stopband is [approximately]40 dB.
01 Jan 2011
TL;DR: Moseev, D., Stejner Pedersen, M., Korsholm, S. as discussed by the authors, Meo, F., Bindslev, H., Bürger, A., Furtula, V., Leipold, F.
Abstract: General information State: Published Organisations: Plasma Physics and Technology Programme, Risø National Laboratory for Sustainable Energy, Forschungszentrum Jülich GmbH, FOM Institute for Plasma Physics RIJNHUIZEN Contributors: Moseev, D., Stejner Pedersen, M., Korsholm, S. B., Meo, F., Bindslev, H., Bürger, A., Furtula, V., Leipold, F. , Listopad, A., Michelsen, P., Nielsen, S. K., Salewski, M., Westerhof, E. Pages: P4.079 Publication date: 2011
01 Jan 2011
TL;DR: Kusano et al. as mentioned in this paper proposed a composites mechanics and materials mechanics (CMLM) approach for wind energy and applied it in the field of nanotechnical engineering.
Abstract: General information Publication status: Published Organisations: Composites Mechanics and Materials Mechanics, Department of Wind Energy, Department of Microand Nanotechnology, Department of Physics, Plasma Physics and Fusion Energy, Department of Management Engineering Contributors: Kusano, Y., Løgstrup Andersen, T., Sørensen, B. F., Rozlosnik, N., Mortensen, H., Teodoru, S., Kingshott, P., Leipold, F., Singh, S. V., Bilde-Sørensen, J., Brøndsted, P., Michelsen, P., Bindslev, H., Bardenshtein, A., Krebs, N. Publication date: 2011