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Atmospheric Pressure Plasma Jet for Mass Spectrometry

100%
EN
The atmospheric pressure plasma is much advantageous over low pressure plasmas in various aspects, e.g. vacuum-free operation, relative low cost, flexibility of a continuous process. Among various plasmas generated in atmospheric pressure discharges there are cold plasma jets that represent a technology of great application promise (industry, medicine, biology). To generate low-temperature plasmas at atmospheric pressure the dielectric barrier discharge can be used. It is suitable for the atomization of volatile species and can also be served as a ionization source for ambient mass and ion mobility spectrometry. As the discharge is generated in a restricted electrode structure, a plasma jet (plume) is usually formed outside the electrode region (that provides spatial separation of the plasma generation and surface processing regions). The paper presents a source based on a plasma jet established at the end of a capillary dielectric barrier discharge at atmospheric pressure and its application to mass spectrometry. The structure of the jet generator consists of piezoelectric transformer and two concentric and symmetric electrodes, between which the working gas flows at definite rate. Besides the source description early results of spectroscopic analysis are also given.
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vol. 125
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issue 6
1326-1329
EN
In this paper, results of spectroscopic study of microwave (2.45 GHz) plasma at atmospheric pressure and high CO_2 flow rate are presented. The plasma was generated by waveguide-supplied nozzleless cylindrical type microwave plasma source. Working gas flow rate and microwave absorbed power varied from 50 up to 150 l/min and from 1 up to 5.5 kW, respectively. The emission spectra in the range of 300-600 nm were recorded. The rotational and vibrational temperatures of C_2 molecules, as well as the rotational temperature of OH radicals were determined by comparing the measured and simulated spectra. The plasma gas temperature inferred from rotational temperature of heavy species ranged from 4000 to 6000 K. It depended on location in plasma, microwave absorbed power and working gas flow rate. The presented microwave plasma source can be used in various gas processing applications.
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vol. 125
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issue 6
1323-1326
EN
The aim of this paper is to present a novel microwave microplasma source generated in different gases at atmospheric pressure. The design, rule of operation and experimental investigations of the new microwave microplasma source are described. The main advantage of the presented microwave microplasma source is its small size, simplicity, and low cost of construction and operation. The microplasma has a form of a small plasma jet of dimensions of a few mm, depending on the kind of gas, gas flow rate, and absorbed microwave power. Presented in this paper results of experimental investigations were obtained with an atmospheric pressure argon, krypton, nitrogen, and air microplasma, sustained by microwaves of standard frequency of 2.45 GHz. The absorbed microwave power was up to 70 W. The gas flow rate was from 2 to 25 l/min. The miniature size, simplicity of the source and stability of the microplasma allow to conclude that the presented new microwave microplasma source can find practical applications in various fields.
4
70%
EN
Various imaging methods and techniques capable of reaching a nanometer spatial resolution are currently under development. One of them is an extreme ultraviolet microscopy, based on the Fresnel zone plates. In this paper a compact, high-repetition, laser-plasma EUV source, with a gas puff target, capable of emitting quasi-monochromatic radiation at 13.8 nm wavelength was used in the first demonstration of a desk-top EUV transmission microscopy with a spatial (half-pitch) resolution of 50 nm. EUV microscopy images of objects with various thicknesses and the spatial resolution measurements using the knife-edge test are presented.
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70%
EN
The area of microbial inactivation by the low-temperature plasma produced by DC electric cometary discharge is increased by insertion of an electrically insulated metallic grid between the discharge and the target object. Gram-negative bacteria are almost fully inactivated; an additional zone of incomplete inactivation appears for Gram-positive bacteria and yeasts.
6
Content available remote

Novel Modulator Topology for Corona Plasma Generation

61%
EN
Gas cleaning using plasma technology is slowly introduced into industry nowadays. Several challenges still have to be overcome: increasing the scale, safety, life-time and reducing costs. In 2006 we demonstrated a 20 kW nanosecond pulsed corona system. The electrical efficiency was > 90%. O-radical yields were found to be very high (3-7 mole/kWh). However, to be competitive, high costs of the pulsed power technology are still a major hurdle. Here we present a novel modulator for efficient generation of large volume corona plasma. Only a small amount of expensive high-voltage components are required. Switching is done at an intermediate voltage level of 1 kV with standard thyristors. At the high-voltage side, only a diode and a pulse transformer are needed. The estimated costs are about 5 kEuro/kW, whereas for state-of-the-art pulsed power technology these costs usually are about 20-30 kEuro/kW. Detailed investigations on the modulator and a wire-plate corona reactor will be presented. Modulator parameters have been varied systematically as well as reactor parameters (number of electrodes, electrode-plate distance). The O-radical yield was determined from the measured ozone concentrations at the exhaust of the reactor. With a detailed kinetic model, ozone concentrations could be calculated back to the initial O*-yields. The following conclusions will be discussed: for all parameters, an electrical efficiency of > 90% could be obtained. With fast imaging, the average streamer width was found to be ∼ 737 μm and an estimate for the plasma volume was made. The obtained yields of O-radicals (1-4 mole/kWh) are excellent. The conditions to obtain high yields will be discussed.
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vol. 125
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issue 6
1309-1312
EN
We present optimization of energy transfer in the waveguide-supplied metal-cylinder-based microwave plasma module with an inner cylindrical quartz tube. The construction of microwave plasma module is based on a WR 340 waveguide standard. Presented microwave plasma module operates at atmospheric pressure and frequency of 2.45 GHz. There is a reduced height section waveguide in microwave plasma module which provides local increase of the electric field in the plasma region. Microwave plasma module is terminated with a movable plunger which plays the role of the tuning element. Tuning characteristics of microwave plasma module are defined as the dependence of the P_{R}/P_{I} on the position l_{s} of the movable plunger, where P_{R} and P_{I} are the microwave power reflected and power incident, respectively. The powers P_{R} and P_{I} are measured in the input plane of microwave plasma module. The purpose of the presented optimization is to achieve P_{R} lower than 5% of P_{I} in widest range of position of movable plunger l_{s}. We used Comsol Multiphysics software to make numerical analysis which allows to optimize the parameters of microwave plasma module. Results of numerical analysis show that P_{R}/P_{I} is lower than 0.05 in a wide range of movable plunger position l_{s}.
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