Klaus-dieter Weltmann | Leibniz Institute for Plasma Science and Technology (original) (raw)

Papers by Klaus-dieter Weltmann

International Conference on Gas Discharges and Their Applications, Sep 1, 2008

Modern notations don't foresee principle differences in cathode spot mechanisms after a few t... more Modern notations don't foresee principle differences in cathode spot mechanisms after a few tens of nanoseconds after discharge ignition. Really, cathode spots generate similar craters regardless of discharge burning time under the condition of cold cathode. The cathode spot plasma has almost stable parameters in the microsecond time scale while gradual changes in the plasma parameters can convincingly be explained with cathode heating effects. However, invariability of spot mechanisms is not the feature of initial period of spot burning since the moment of gap breakdown. We recently observed a surprising behaviour of cathode spot plasma characteristics within the first microsecond of discharge burning. Though ion energies per charge ratios are the same for all charge states at the long-burning arc discharge, there is a dependency of the ratios on charge states in the starting phase. The similar transition is seen in spot light radiation. Higher ion charge state lines start to shine first, being followed by lower charge state lines. Finally, atomic lines appeared after the delay as long as half microsecond. The latter fact correlates with exactly the same delay of resonant absorption by spot plasma at atomic lines.

The optical emission of single cathode spots is studied to improve the understanding of the vacuu... more The optical emission of single cathode spots is studied to improve the understanding of the vacuum spot initiation and dynamics.

International Conference on Gas Discharges and Their Applications, Sep 1, 2008

ABSTRACT Plasma torches are widely used for deposition processes. Optimum burner design and opera... more ABSTRACT Plasma torches are widely used for deposition processes. Optimum burner design and operation conditions help to save large amount of energy and environmental pollution. This can be considerably supported by modeling. A coupled 3D MHD-simulation of an inductively coupled plasma torch and the deposition process of SiO2 on a moving target has been performed. The steady-state continuity, momentum and enthalpy equations are solved assuming local thermal and chemical equilibrium (LTE) and laminar flow. The energy coupling to the plasma accomplished through the electromagnetic field of an induction coil and the radiation losses from the plasma are accounted for in the discretized fluid enthalpy equation as source terms. For all species considered in the system a transport equation is solved. The surface reaction governing the deposition process provides a boundary condition for the species mass fractions in the fluid. The model developed supplies information about the temperature and velocity distribution of the fluid components and the deposition rate on the target surface for complex real geometries.

A simple numerical model for the assessment of the arc stability in AMF electrode systems is sugg... more A simple numerical model for the assessment of the arc stability in AMF electrode systems is suggested. The model combines electromagnetic simulations with simplified plasma description. The plasma model prescribes the basic features of the arc column which moves in accordance with the action of the Lorentz force. Analysis of the plasma trajectory indicates the stability of the arc column considering the lateral displacement toward the metal vapor condensation shield. The model has been used for analysis of the influence of contact geometry on the arc movement. Results are shown for a typical AMF contact system.

ABSTRACT form only given. Thermal plasma processes are frequently accompanied with large energy c... more ABSTRACT form only given. Thermal plasma processes are frequently accompanied with large energy consumption and environmental pollution. Optimum design and operation conditions help to reduce these concomitants and the production costs. Such an optimization can be considerably supported by modeling. An inductively coupled plasma torch for the silicon oxide deposition as it is typically applied for fiber preform production is studied by simulations. The analysis focuses on the induction process, the flow and plasma properties as well as the deposition process. A burner made by three cylindrical quartz tubes and a copper coil with five turns operated with 25 kW RF power at 3 MHz is considered. Oxygen (30 slm) and Nitrogen (120 slm) are used as plasma and sheath gas, respectively, at atmospheric pressure. For the outside vapor deposition process the precursor SiCl4 (2 kg/h) is fed through a nozzle in the torch center below the heating zone. The cylindrical preform target rotates (1 s"1) and laterally moves (0.18 m/min) in a distance of 4.2 cm above the burner. A 3D MHD-simulation method has been developed for the torch plasma based on the CFD-ACE+ commercial package. The steady state continuity, momentum and enthalpy equations are solved assuming local thermal and chemical equilibrium and laminar flow. This system is coupled with the electromagnetic equations to describe the induction process self-consistently. For all species considered in the system a transport equation is solved. The surface reaction governing the deposition process provides a boundary condition for the species mass fractions in the fluid.The simulation provides inside into the realistic spatial behavior of temperature, flow and mixing of the species. The calculated deposition rate on the substrate is illustrated in Fig. 1. In addition, the deposition on critical parts of the burner has been studied. The simulation method developed is suitable for burner design optimization as well as for deducing i- proved operation conditions.

Measurement Science and Technology, May 14, 2014

ABSTRACT Using a vector network analyzer a frequency resolved microwave interferometer is built u... more ABSTRACT Using a vector network analyzer a frequency resolved microwave interferometer is built up in the range of 42.5–50 GHz. Due to the frequency resolved measurement technique it is possible to investigate the influence of the surrounding dielectric material on the transmission. The experiments are performed on a fluorescent lamp, which is enclosed by a glass tube. Furthermore, a dielectric resonator is built up by two plane silica windows, placed perpendicular to the beam. It was found that the influence can be described by a one-dimensional model using equivalent circuits, which is in very good agreement with experimental results. In addition, the common technique of rotating the windows to reduce their influence is investigated.

Summary form only given. Generation of an anode flare in the initial stage of vacuum discharge wa... more Summary form only given. Generation of an anode flare in the initial stage of vacuum discharge was studied. Discharge gap was formed by a liquid-metal gallium-indium point cathode and a flat anode of the same material, with an electrode gap distance of 0.8-1 mm. The discharge was fed by pulse generator with an impedance of 50 Ohm, generating a rectangular pulse with a duration of 200 ns. Estimates show that with a charging voltage of 15-25 kV and a current amplitude of 150-250 A we can expect that power density at the anode surface could be as high as 108 W/cm2.Using a spectrometer combined with a intensified CCD camera, spatial and spatio-spectral pattern of plasma emission from the discharge gap were registered with a temporal resolution of 10 ns. Generation of the anode flare begins with the intensive evaporation of anode material in the spark (high-voltage) stage of the discharge. In this period, only lines of neutral atoms are present in the spectrum measured at anode position although higher charge states can be found in the cathode spectra. Intensive ionization of anode flare atoms starts when the discharge changes from the spark to an arc (low-voltage) stage. Lines of single and double charged ions consistently appear in the spectrum (lines of ions with a higher charge state were not available for registration). At the subsequent expansion of anode flare, the highest expansion velocity was observed for double charged ion lines, and the lowest one was found for neutral atoms. Expansion velocity was increasing with increasing a voltage and current (enhancement of the input energy). The mechanisms of evaporation, ionization, ion acceleration, and the role of the anode flare in the discharge are discussed.

IEEE Transactions on Plasma Science, Oct 1, 2014

ABSTRACT The knowledge of the distribution of electromagnetic field and plasma parameters is of c... more ABSTRACT The knowledge of the distribution of electromagnetic field and plasma parameters is of crucial importance for the development of microwave plasma sources. To that purpose, a time-dependent 2-D fluid model accompanying experiments has been applied to investigate the coupling between the plasma flow and kinetics and the propagating microwaves.

This paper presents the results of time and space resolved optical investigations of high-current... more This paper presents the results of time and space resolved optical investigations of high-current vacuum arcs by means of video spectroscopy. Especially, the transition from the diffuse mode to constricted modes (footpoint, intense or spot mode) has been studied in dependency on the arc current and instantaneous electrode distance. The driving current pulse from a high-current generator which corresponds to the pulsed DC 10 ms was applied. Spectral lines of Cu I, Cu II, and Cu III have been analyzed for various anode modes using a combination of spectrograph and high-speed camera.

Plasma medicine, 2016

Currently used disinfection and sanitation methods for fresh fruits and vegetables lack antimicro... more Currently used disinfection and sanitation methods for fresh fruits and vegetables lack antimicrobial effectiveness and are high in cost, water consumption, or chemicals. One alternative may be nonthermal plasma at atmospheric pressure. The plasma setup used depends on microwave plasma, which generates plasma-processed air (PPA) with manifold chemical and antimicrobial compounds mainly based on reactive nitrogen species. yeast, and endospores) and then treated with PPA. After a maximum treatment time of 15 min, reduction rates greater than 5 log were achieved. Furthermore, sensory examination Clearly, plasma and the generated chemical mixture that leads to high microbial inactivation on specimens offer a wide range of possible uses. However, food quality must be further investigated.

Vakuum in Forschung und Praxis, 2020

Advanced optical diagnostics of vacuum arc plasma for switching applications

IEEE Transactions on Plasma Science, 2016

This paper presents the impact of current waveform and frequency on the formation of high-current... more This paper presents the impact of current waveform and frequency on the formation of high-current anode phenomena in a vacuum interrupter experiment. Different waveforms including the alternative current pulses of 50, 180, and 260 Hz and direct current pulses of 5 and 10 ms are compared. The impact of different opening times and contact speeds on the highcurrent anode mode formation is investigated. The results show that both instantaneous current and total transferred charge are important in the formation of high-current anode modes. Therefore, the arcing time has a strong influence. Two types of anode spot modes with different electrical and optical characteristics are also observed. The transitions between different highcurrent modes are examined systematically, resulting in existence areas dependent on threshold current and gap length. The latter are determined for different contact materials including Cu, CuCr7525, and CuCr50 and different contact diameters.

Plasma Processes and Polymers, 2018

The application of gas discharge plasmas has assumed an important place in many manufacturing pro... more The application of gas discharge plasmas has assumed an important place in many manufacturing processes. Plasma methods contribute significantly to the economic prosperity of industrialized societies. However, plasma is mainly an enabling method and therefore its role remains often hidden. Hence the success of plasma technologies is described for different examples and commercial areas. From these examples and emerging applications, the potential of plasma technologies is discussed. Economic trends are anticipated together with research needs. The community of plasma scientists strongly believes that more exciting advances will continue to foster innovations and discoveries in the first decades of the 21st century, if research and education will be properly funded and sustained by public bodies and industrial investors.

Plasma Processes and Polymers, Feb 14, 2012

Plasma medicine has become an emerging field in medical sciences since cold plasma has demonstrat... more Plasma medicine has become an emerging field in medical sciences since cold plasma has demonstrated anti‐inflammatory, anti‐tumor as well as antimicrobial effects. In the light of increasing resistance of many pathogens like methicillin‐resistant Staphylococcus aureus (MRSA) to a multitude of antimicrobial therapies cold plasma therapy with complete different modes of action could constitute an alternative to conventional external antibiotic and antiseptic therapies. As plasma susceptibility data of human skin and wound pathogens are not available, the susceptibility of 105 typical isolates from dermatologic patients' wounds to low temperature atmospheric pressure plasma (APPJ device) and dielectric barrier discharge plasma device are tested in vitro. Plasma treatment proved to be highly effective in eradicating all (n = 105) strains including Escherichia coli, Pseudomonas aeruginosa, Klebsiella group (K. pneumoniae ssp. pneumoniae, K. oxytoca), S. aureus, hemolysing Lancefield Streptococci (group A and B), Proteus group (P. mirabilis, P. vulgaris), Acinetobacter spp., Stenotrophomonas spp., Enterococcus faecalis, Candida albicans and Staphylococcus epidermidis. In conclusion, cold plasma treatment exhibited strong and rapid antimicrobial effects against clinical most relevant skin and wound pathogens in vitro. Cold plasma may constitute an effective alternative to antiseptics in the attempt to eradicate skin and wound pathogens.magnified image

Clinical Plasma Medicine, Jun 1, 2013

The medical application of cold physical plasma is a new, innovative therapy concept in human med... more The medical application of cold physical plasma is a new, innovative therapy concept in human medicine, which became internationally established as a new research field with the name ''plasma medicine''. Antimicrobial effects, as well as non-lethal, cell and tissue selectively and controllably modifying plasma effects are the basis for the application of physical plasmas. With this application, several active components that are known and medically well established (UV-rays, reactive oxygen species/ozone, reactive nitrogen species, electric fields, pH-reduction and temperature) are being combined. What makes plasma applications so special are the facts that:

Bulletin of the American Physical Society, Nov 5, 2014

the generation of radicals in plasma treated liquids has been investigated. To quantify the contr... more the generation of radicals in plasma treated liquids has been investigated. To quantify the contribution of plasma vacuum ultraviolet (VUV) and ultraviolet (UV) radiation on the species investigated, three cases have been studied: UV of plasma jet only, UV and VUV of plasma jet combined, and the plasma effluent including all reactive components. The emitted VUV has been observed by optical emission spectroscopy and its effect on radical formation in liquids has been analyzed by electron spin resonance spectroscopy. Radicals have been determined in ultrapure water (dH 2 O), as well as in more complex, biorelevant solutions like phosphate buffered saline (PBS) solution, and two different cell culture media. Various compositions lead to different reactive species formation, e.g. in PBS superoxide anion and hydroxyl radicals have been detected, in cell suspension also glutathione thiyl radicals have been found. This study highlights that UV has no impact on radical generation, whereas VUV is relevant for producing radicals. VUV treatment of dH 2 O generates one third of the radical concentration produced by plasma-effluent treatment. It is relevant for plasma medicine because although plasma sources are operated in open air atmosphere, still VUV can lead to formation of biorelevant radicals.

ABSTRACT form only given. Plasma medicine and also inactivation of bacteria with physical plasmas... more ABSTRACT form only given. Plasma medicine and also inactivation of bacteria with physical plasmas is a promising new field of life science with huge interest especially for medical applications. Despite numerous successful applications of low temperature gas plasmas in medicine and decontamination, the fundamental nature of the interactions between plasma and microorganisms is to a large extent unknown. A detailed knowledge of these interactions is essential for the development of new as well as for the enhancement of established plasma treatment procedures.In the present work we introduce a growth chamber system suitable for physical plasma treatment of bacteria in liquid medium. The gram positive model organism Bacillus subtilis was treated with plasma, in order to investigate the specific stress response using a proteomic and transcriptomic approach. Two different gas admixtures as well as different discharge voltages were applied during the plasma treatment. We were able to connect reactive agents produced in the plasma with the specific cellular response. This response displayed a clear correlation in dependence of the used gas and the plasma power. B. subtilis faces e.g. different kinds of cell wall stress, depending on the used gas, which was made visible also by electron microscopy. Furthermore, the extent of DNA damages and oxidative stress differed significantly, again, depending on the used gas and plasma power. The biological findings could be supported by the diagnostic of reactive plasma species.

Journal of physics, May 1, 2010

The method of laser induced fluorescence (LIF) is applied to fluorescent lamps (FL) in order to i... more The method of laser induced fluorescence (LIF) is applied to fluorescent lamps (FL) in order to investigate processes of electrode erosion in the vicinity of the electrodes. The life time of FLs which are ignited by instant start is mainly limited by sputtering of the coil electrodes and in final breaking. This sputtering of tungsten mainly occurs during the ignition in the glow discharge phase. Therefore, the density of W atoms is measured in the electrode region during ignition. Temporal and spatial resolved profiles were measured by LIF which has been combined with fast imaging. The life time of FLs which are started with preheated coils is also caused mainly by electrode failures. But the reason differs from the instant start case because here the loss is caused mainly by evaporation. End-of-lamp life is reached if the emitter material which is deposited at the coil to reduce the work function of the coil is lost completely. LIF is used to measure the density of the eroded emitter material, namely Barium atoms. First result of phase resolved absolute Ba atoms densities are presented.

International Conference on Gas Discharges and Their Applications, Sep 1, 2008

Modern notations don't foresee principle differences in cathode spot mechanisms after a few t... more Modern notations don't foresee principle differences in cathode spot mechanisms after a few tens of nanoseconds after discharge ignition. Really, cathode spots generate similar craters regardless of discharge burning time under the condition of cold cathode. The cathode spot plasma has almost stable parameters in the microsecond time scale while gradual changes in the plasma parameters can convincingly be explained with cathode heating effects. However, invariability of spot mechanisms is not the feature of initial period of spot burning since the moment of gap breakdown. We recently observed a surprising behaviour of cathode spot plasma characteristics within the first microsecond of discharge burning. Though ion energies per charge ratios are the same for all charge states at the long-burning arc discharge, there is a dependency of the ratios on charge states in the starting phase. The similar transition is seen in spot light radiation. Higher ion charge state lines start to shine first, being followed by lower charge state lines. Finally, atomic lines appeared after the delay as long as half microsecond. The latter fact correlates with exactly the same delay of resonant absorption by spot plasma at atomic lines.

The optical emission of single cathode spots is studied to improve the understanding of the vacuu... more The optical emission of single cathode spots is studied to improve the understanding of the vacuum spot initiation and dynamics.

International Conference on Gas Discharges and Their Applications, Sep 1, 2008

ABSTRACT Plasma torches are widely used for deposition processes. Optimum burner design and opera... more ABSTRACT Plasma torches are widely used for deposition processes. Optimum burner design and operation conditions help to save large amount of energy and environmental pollution. This can be considerably supported by modeling. A coupled 3D MHD-simulation of an inductively coupled plasma torch and the deposition process of SiO2 on a moving target has been performed. The steady-state continuity, momentum and enthalpy equations are solved assuming local thermal and chemical equilibrium (LTE) and laminar flow. The energy coupling to the plasma accomplished through the electromagnetic field of an induction coil and the radiation losses from the plasma are accounted for in the discretized fluid enthalpy equation as source terms. For all species considered in the system a transport equation is solved. The surface reaction governing the deposition process provides a boundary condition for the species mass fractions in the fluid. The model developed supplies information about the temperature and velocity distribution of the fluid components and the deposition rate on the target surface for complex real geometries.

A simple numerical model for the assessment of the arc stability in AMF electrode systems is sugg... more A simple numerical model for the assessment of the arc stability in AMF electrode systems is suggested. The model combines electromagnetic simulations with simplified plasma description. The plasma model prescribes the basic features of the arc column which moves in accordance with the action of the Lorentz force. Analysis of the plasma trajectory indicates the stability of the arc column considering the lateral displacement toward the metal vapor condensation shield. The model has been used for analysis of the influence of contact geometry on the arc movement. Results are shown for a typical AMF contact system.

ABSTRACT form only given. Thermal plasma processes are frequently accompanied with large energy c... more ABSTRACT form only given. Thermal plasma processes are frequently accompanied with large energy consumption and environmental pollution. Optimum design and operation conditions help to reduce these concomitants and the production costs. Such an optimization can be considerably supported by modeling. An inductively coupled plasma torch for the silicon oxide deposition as it is typically applied for fiber preform production is studied by simulations. The analysis focuses on the induction process, the flow and plasma properties as well as the deposition process. A burner made by three cylindrical quartz tubes and a copper coil with five turns operated with 25 kW RF power at 3 MHz is considered. Oxygen (30 slm) and Nitrogen (120 slm) are used as plasma and sheath gas, respectively, at atmospheric pressure. For the outside vapor deposition process the precursor SiCl4 (2 kg/h) is fed through a nozzle in the torch center below the heating zone. The cylindrical preform target rotates (1 s"1) and laterally moves (0.18 m/min) in a distance of 4.2 cm above the burner. A 3D MHD-simulation method has been developed for the torch plasma based on the CFD-ACE+ commercial package. The steady state continuity, momentum and enthalpy equations are solved assuming local thermal and chemical equilibrium and laminar flow. This system is coupled with the electromagnetic equations to describe the induction process self-consistently. For all species considered in the system a transport equation is solved. The surface reaction governing the deposition process provides a boundary condition for the species mass fractions in the fluid.The simulation provides inside into the realistic spatial behavior of temperature, flow and mixing of the species. The calculated deposition rate on the substrate is illustrated in Fig. 1. In addition, the deposition on critical parts of the burner has been studied. The simulation method developed is suitable for burner design optimization as well as for deducing i- proved operation conditions.

Measurement Science and Technology, May 14, 2014

ABSTRACT Using a vector network analyzer a frequency resolved microwave interferometer is built u... more ABSTRACT Using a vector network analyzer a frequency resolved microwave interferometer is built up in the range of 42.5–50 GHz. Due to the frequency resolved measurement technique it is possible to investigate the influence of the surrounding dielectric material on the transmission. The experiments are performed on a fluorescent lamp, which is enclosed by a glass tube. Furthermore, a dielectric resonator is built up by two plane silica windows, placed perpendicular to the beam. It was found that the influence can be described by a one-dimensional model using equivalent circuits, which is in very good agreement with experimental results. In addition, the common technique of rotating the windows to reduce their influence is investigated.

Summary form only given. Generation of an anode flare in the initial stage of vacuum discharge wa... more Summary form only given. Generation of an anode flare in the initial stage of vacuum discharge was studied. Discharge gap was formed by a liquid-metal gallium-indium point cathode and a flat anode of the same material, with an electrode gap distance of 0.8-1 mm. The discharge was fed by pulse generator with an impedance of 50 Ohm, generating a rectangular pulse with a duration of 200 ns. Estimates show that with a charging voltage of 15-25 kV and a current amplitude of 150-250 A we can expect that power density at the anode surface could be as high as 108 W/cm2.Using a spectrometer combined with a intensified CCD camera, spatial and spatio-spectral pattern of plasma emission from the discharge gap were registered with a temporal resolution of 10 ns. Generation of the anode flare begins with the intensive evaporation of anode material in the spark (high-voltage) stage of the discharge. In this period, only lines of neutral atoms are present in the spectrum measured at anode position although higher charge states can be found in the cathode spectra. Intensive ionization of anode flare atoms starts when the discharge changes from the spark to an arc (low-voltage) stage. Lines of single and double charged ions consistently appear in the spectrum (lines of ions with a higher charge state were not available for registration). At the subsequent expansion of anode flare, the highest expansion velocity was observed for double charged ion lines, and the lowest one was found for neutral atoms. Expansion velocity was increasing with increasing a voltage and current (enhancement of the input energy). The mechanisms of evaporation, ionization, ion acceleration, and the role of the anode flare in the discharge are discussed.

IEEE Transactions on Plasma Science, Oct 1, 2014

ABSTRACT The knowledge of the distribution of electromagnetic field and plasma parameters is of c... more ABSTRACT The knowledge of the distribution of electromagnetic field and plasma parameters is of crucial importance for the development of microwave plasma sources. To that purpose, a time-dependent 2-D fluid model accompanying experiments has been applied to investigate the coupling between the plasma flow and kinetics and the propagating microwaves.

This paper presents the results of time and space resolved optical investigations of high-current... more This paper presents the results of time and space resolved optical investigations of high-current vacuum arcs by means of video spectroscopy. Especially, the transition from the diffuse mode to constricted modes (footpoint, intense or spot mode) has been studied in dependency on the arc current and instantaneous electrode distance. The driving current pulse from a high-current generator which corresponds to the pulsed DC 10 ms was applied. Spectral lines of Cu I, Cu II, and Cu III have been analyzed for various anode modes using a combination of spectrograph and high-speed camera.

Plasma medicine, 2016

Currently used disinfection and sanitation methods for fresh fruits and vegetables lack antimicro... more Currently used disinfection and sanitation methods for fresh fruits and vegetables lack antimicrobial effectiveness and are high in cost, water consumption, or chemicals. One alternative may be nonthermal plasma at atmospheric pressure. The plasma setup used depends on microwave plasma, which generates plasma-processed air (PPA) with manifold chemical and antimicrobial compounds mainly based on reactive nitrogen species. yeast, and endospores) and then treated with PPA. After a maximum treatment time of 15 min, reduction rates greater than 5 log were achieved. Furthermore, sensory examination Clearly, plasma and the generated chemical mixture that leads to high microbial inactivation on specimens offer a wide range of possible uses. However, food quality must be further investigated.

Vakuum in Forschung und Praxis, 2020

Advanced optical diagnostics of vacuum arc plasma for switching applications

IEEE Transactions on Plasma Science, 2016

This paper presents the impact of current waveform and frequency on the formation of high-current... more This paper presents the impact of current waveform and frequency on the formation of high-current anode phenomena in a vacuum interrupter experiment. Different waveforms including the alternative current pulses of 50, 180, and 260 Hz and direct current pulses of 5 and 10 ms are compared. The impact of different opening times and contact speeds on the highcurrent anode mode formation is investigated. The results show that both instantaneous current and total transferred charge are important in the formation of high-current anode modes. Therefore, the arcing time has a strong influence. Two types of anode spot modes with different electrical and optical characteristics are also observed. The transitions between different highcurrent modes are examined systematically, resulting in existence areas dependent on threshold current and gap length. The latter are determined for different contact materials including Cu, CuCr7525, and CuCr50 and different contact diameters.

Plasma Processes and Polymers, 2018

The application of gas discharge plasmas has assumed an important place in many manufacturing pro... more The application of gas discharge plasmas has assumed an important place in many manufacturing processes. Plasma methods contribute significantly to the economic prosperity of industrialized societies. However, plasma is mainly an enabling method and therefore its role remains often hidden. Hence the success of plasma technologies is described for different examples and commercial areas. From these examples and emerging applications, the potential of plasma technologies is discussed. Economic trends are anticipated together with research needs. The community of plasma scientists strongly believes that more exciting advances will continue to foster innovations and discoveries in the first decades of the 21st century, if research and education will be properly funded and sustained by public bodies and industrial investors.

Plasma Processes and Polymers, Feb 14, 2012

Plasma medicine has become an emerging field in medical sciences since cold plasma has demonstrat... more Plasma medicine has become an emerging field in medical sciences since cold plasma has demonstrated anti‐inflammatory, anti‐tumor as well as antimicrobial effects. In the light of increasing resistance of many pathogens like methicillin‐resistant Staphylococcus aureus (MRSA) to a multitude of antimicrobial therapies cold plasma therapy with complete different modes of action could constitute an alternative to conventional external antibiotic and antiseptic therapies. As plasma susceptibility data of human skin and wound pathogens are not available, the susceptibility of 105 typical isolates from dermatologic patients' wounds to low temperature atmospheric pressure plasma (APPJ device) and dielectric barrier discharge plasma device are tested in vitro. Plasma treatment proved to be highly effective in eradicating all (n = 105) strains including Escherichia coli, Pseudomonas aeruginosa, Klebsiella group (K. pneumoniae ssp. pneumoniae, K. oxytoca), S. aureus, hemolysing Lancefield Streptococci (group A and B), Proteus group (P. mirabilis, P. vulgaris), Acinetobacter spp., Stenotrophomonas spp., Enterococcus faecalis, Candida albicans and Staphylococcus epidermidis. In conclusion, cold plasma treatment exhibited strong and rapid antimicrobial effects against clinical most relevant skin and wound pathogens in vitro. Cold plasma may constitute an effective alternative to antiseptics in the attempt to eradicate skin and wound pathogens.magnified image

Clinical Plasma Medicine, Jun 1, 2013

The medical application of cold physical plasma is a new, innovative therapy concept in human med... more The medical application of cold physical plasma is a new, innovative therapy concept in human medicine, which became internationally established as a new research field with the name ''plasma medicine''. Antimicrobial effects, as well as non-lethal, cell and tissue selectively and controllably modifying plasma effects are the basis for the application of physical plasmas. With this application, several active components that are known and medically well established (UV-rays, reactive oxygen species/ozone, reactive nitrogen species, electric fields, pH-reduction and temperature) are being combined. What makes plasma applications so special are the facts that:

Bulletin of the American Physical Society, Nov 5, 2014

the generation of radicals in plasma treated liquids has been investigated. To quantify the contr... more the generation of radicals in plasma treated liquids has been investigated. To quantify the contribution of plasma vacuum ultraviolet (VUV) and ultraviolet (UV) radiation on the species investigated, three cases have been studied: UV of plasma jet only, UV and VUV of plasma jet combined, and the plasma effluent including all reactive components. The emitted VUV has been observed by optical emission spectroscopy and its effect on radical formation in liquids has been analyzed by electron spin resonance spectroscopy. Radicals have been determined in ultrapure water (dH 2 O), as well as in more complex, biorelevant solutions like phosphate buffered saline (PBS) solution, and two different cell culture media. Various compositions lead to different reactive species formation, e.g. in PBS superoxide anion and hydroxyl radicals have been detected, in cell suspension also glutathione thiyl radicals have been found. This study highlights that UV has no impact on radical generation, whereas VUV is relevant for producing radicals. VUV treatment of dH 2 O generates one third of the radical concentration produced by plasma-effluent treatment. It is relevant for plasma medicine because although plasma sources are operated in open air atmosphere, still VUV can lead to formation of biorelevant radicals.

ABSTRACT form only given. Plasma medicine and also inactivation of bacteria with physical plasmas... more ABSTRACT form only given. Plasma medicine and also inactivation of bacteria with physical plasmas is a promising new field of life science with huge interest especially for medical applications. Despite numerous successful applications of low temperature gas plasmas in medicine and decontamination, the fundamental nature of the interactions between plasma and microorganisms is to a large extent unknown. A detailed knowledge of these interactions is essential for the development of new as well as for the enhancement of established plasma treatment procedures.In the present work we introduce a growth chamber system suitable for physical plasma treatment of bacteria in liquid medium. The gram positive model organism Bacillus subtilis was treated with plasma, in order to investigate the specific stress response using a proteomic and transcriptomic approach. Two different gas admixtures as well as different discharge voltages were applied during the plasma treatment. We were able to connect reactive agents produced in the plasma with the specific cellular response. This response displayed a clear correlation in dependence of the used gas and the plasma power. B. subtilis faces e.g. different kinds of cell wall stress, depending on the used gas, which was made visible also by electron microscopy. Furthermore, the extent of DNA damages and oxidative stress differed significantly, again, depending on the used gas and plasma power. The biological findings could be supported by the diagnostic of reactive plasma species.

Journal of physics, May 1, 2010

The method of laser induced fluorescence (LIF) is applied to fluorescent lamps (FL) in order to i... more The method of laser induced fluorescence (LIF) is applied to fluorescent lamps (FL) in order to investigate processes of electrode erosion in the vicinity of the electrodes. The life time of FLs which are ignited by instant start is mainly limited by sputtering of the coil electrodes and in final breaking. This sputtering of tungsten mainly occurs during the ignition in the glow discharge phase. Therefore, the density of W atoms is measured in the electrode region during ignition. Temporal and spatial resolved profiles were measured by LIF which has been combined with fast imaging. The life time of FLs which are started with preheated coils is also caused mainly by electrode failures. But the reason differs from the instant start case because here the loss is caused mainly by evaporation. End-of-lamp life is reached if the emitter material which is deposited at the coil to reduce the work function of the coil is lost completely. LIF is used to measure the density of the eroded emitter material, namely Barium atoms. First result of phase resolved absolute Ba atoms densities are presented.