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Spectroscopic Study of Post-Discharges in Nitrogen and its Mixtures
Mazánková, Věra ; Kapička, Vratislav (referee) ; Hrachová,, Věra (referee) ; Krčma, František (advisor)
Presented thesis gives results obtained during the spectroscopic observations of post –discharges of the pure nitrogen plasma with small oxygen admixture and in the nitrogen – argon mixture and the effect of the pink afterglow in it. The DC discharge in the flowing regime has been used for the plasma generation. The decaying plasma was study by optical emission spectroscopy, mainly in the range of 300–800 nm. The first positive, second positive, first negative nitrogen spectral system and NO spectral systems were observed in measured spectra. The band head intensities of these bands have been studied in the dependencies on experimental conditions. Simultaneously, the relative vibrational populations on the given nitrogen states have been calculated. Two discharge tubes made from different materials (PYREX glass and QUARTZ glass) were used in the case of nitrogen plasma containing low oxygen traces (up to 0.2 %). These experiments have been carried out at two wall temperatures for the determination of the temperature effect on the post-discharge. The discharge tube around the observation point was kept at the ambient temperature (300 K) or it was cooled down to 77 K by liquid nitrogen vapor. The total gas pressure of 1 000 Pa and the discharge current of 200 mA were conserved for all these experiments. The relative populations of electronic states were calculated in the dependence on the post-discharge time. The dependencies on oxygen concentration were given, too. The results showed no simple dependence of vibrational populations on oxygen concentration. Generally, slight increase of neutral nitrogen states populations was observed with the increase of oxygen concentration. These observations were well visible due to the intensity of nitrogen pink afterglow effect that was well visible at all oxygen concentrations. The pink afterglow maximal intensity was reached at about 5–10 ms at the wall temperature of 300 K in the PYREX tube. The molecular ion emission was strongly quenched by the oxygen and as this was dominant process for the pink afterglow emission the pink afterglow effect disappears at oxygen concentration of about 2000 ppm. The temperature and wall material influences were observed, too. The post-discharge in nitrogen argon mixtures was studied only in the PYREX tube at the ambient wall temperature of 300 K. The power dissipated in an active discharge was constant of 290 kW. The experimental studies had two new parameters – total gas pressure (500 Pa – 5 000 Pa) and the argon concentrations that were varied in the range of 0–83 %. Also in this case the dependencies of relative intensities of the bands given above were obtained and further the relative populations of electronic states as a function of decay time, total gas pressure and on argon concentration were obtained. The pink afterglow effect was observed at all applied discharge powers and total gas pressures. At the highest argon concentrations, especially at lower pressure, the pink afterglow effect disappeared. The presented experimental work is one of the hugest sets of experiments in the nitrogen with oxygen traces and in nitrogen-argon mixtures. These data can be used as a very good fundament for the further studies using wide numeric modeling of the post-discharge kinetic processes.
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Study of post-discharge kinetic processes by titration methods
Josiek, Stanislav ; Kozáková, Zdenka (referee) ; Mazánková, Věra (advisor)
Many experimental and theoretical works on plasma post-discharges have been published during the last more than fifty years. A part of these works was focused in details on nitrogen discharges and post-discharges and kinetic processes in it. The aim of the presented bachelor`s thesis was to study kinetic processes in post-discharge in pure nitrogen and nitrogen contained methane traces. Atomic nitrogen concentration at different methane concentrations was measured by the nitrogen monoxide titration into the post-discharge. All experimental results were obtained by the optical emission spectroscopy. Optical emission spectra were taken in the range of 300-600 nm. DC discharge was created in a quartz tube in a flowing regime. The flowing regime was chosen for this experiment because of better time resolution of the post-discharge. Nitrogen flow was 400 mln/min. Nitrogen oxide flow was in the range of 0-10 mln/min and it was added at the selected post-discharge time. Experiments were carried out for pure nitrogen and for four different methane concentrations – 0.006, 0.013, 0.019 and 0.025 %. Total gas pressure of 1000 Pa, discharge current of 150 mA and voltage of 1110 V were constant during all these experiments. Nitrogen first positive, second positive and first negative spectral systems, NO spectral system and NO2* spectral system were recognized in all measured spectra. The atomic nitrogen concentration was determined using NO and NO2* intensities, and it was increased by the increase of methane concentration. On the other hand, the nitrogen molecular ion emission was strongly quenched even at very low concentration of methane. From this point of view, this thesis is innovative and brings new results into the worldwide research.
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Study of molecular oxygen titration into nitrogen post-discharge
Řehulková, Blanka ; Mazánková, Věra (referee) ; Krčma, František (advisor)
A huge number of experiments were carried out in the field of nitrogen post-discharges during the last 50 or 60 years and they were supported by many published theoretical works. Some papers were focused also on the nitrogen active discharge, post-discharge itself, or they focused mainly on the kinetic processes running during the post-discharge period. This experimental work shows how oxygen titration into post-discharge will influence nitrogen flowing post-discharge. Experimental data were obtained by optical emission spectrometry, Spectra were measured in the range 300 - 700 nm at laboratory temperature of 300K. Discharge current was kept constant at the value of 120 mA relating to the total discharge power of 145 W. Pressure was kept constant, too, at the value of 1000 Pa. The nitrogen of 99.9999 % purity (further purified by Oxiclear column) flow was adjusted at 0.8 l/min. Flow of oxygen (99.95 % purity) through he titration capillary introduced to post-discharge from down stream direction, was kept at 4 ml/min. Both gas flows were controlled by mass flow controllers. The optical emission spectrometer Jobin Yvon TRIAX 550 with 300 gr/mm grating equipped by liquid nitrogen cooled CCD detector was used for the spectra acquisition. The integration time of 1 s was used at all experiments. The position of titration tube end introduced into post discharge from the down stream side was set from 5 to 25 cm with respect to the end of the active discharge; the step of 1 cm was used. The optical emission spectra were measured at positions from 3 to 29 cm with respect to the active discharge end. The following nitrogen spectral systems were identified in the spectra: 1st positive, 1st negative and 2nd positive. Besides them, some bands of NO-beta system were found. The intensity profiles along the post discharge were obtained for selected vibrational spectral bands of these spectral systems and changes in the vibrational distributions of upper electronic states of these spectral systems were determined.
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Study of molecular oxygen titration into nitrogen post-discharge
Řehulková, Blanka ; Mazánková, Věra (referee) ; Krčma, František (advisor)
A huge number of experiments were carried out in the field of nitrogen post-discharges during the last 50 or 60 years and they were supported by many published theoretical works. Some papers were focused also on the nitrogen active discharge, post-discharge itself, or they focused mainly on the kinetic processes running during the post-discharge period. This experimental work shows how oxygen titration into post-discharge will influence nitrogen flowing post-discharge. Experimental data were obtained by optical emission spectrometry, Spectra were measured in the range 300 - 700 nm at laboratory temperature of 300K. Discharge current was kept constant at the value of 120 mA relating to the total discharge power of 145 W. Pressure was kept constant, too, at the value of 1000 Pa. The nitrogen of 99.9999 % purity (further purified by Oxiclear column) flow was adjusted at 0.8 l/min. Flow of oxygen (99.95 % purity) through he titration capillary introduced to post-discharge from down stream direction, was kept at 4 ml/min. Both gas flows were controlled by mass flow controllers. The optical emission spectrometer Jobin Yvon TRIAX 550 with 300 gr/mm grating equipped by liquid nitrogen cooled CCD detector was used for the spectra acquisition. The integration time of 1 s was used at all experiments. The position of titration tube end introduced into post discharge from the down stream side was set from 5 to 25 cm with respect to the end of the active discharge; the step of 1 cm was used. The optical emission spectra were measured at positions from 3 to 29 cm with respect to the active discharge end. The following nitrogen spectral systems were identified in the spectra: 1st positive, 1st negative and 2nd positive. Besides them, some bands of NO-beta system were found. The intensity profiles along the post discharge were obtained for selected vibrational spectral bands of these spectral systems and changes in the vibrational distributions of upper electronic states of these spectral systems were determined.
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Spectroscopic Study of Post-Discharges in Nitrogen and its Mixtures
Mazánková, Věra ; Kapička, Vratislav (referee) ; Hrachová,, Věra (referee) ; Krčma, František (advisor)
Presented thesis gives results obtained during the spectroscopic observations of post –discharges of the pure nitrogen plasma with small oxygen admixture and in the nitrogen – argon mixture and the effect of the pink afterglow in it. The DC discharge in the flowing regime has been used for the plasma generation. The decaying plasma was study by optical emission spectroscopy, mainly in the range of 300–800 nm. The first positive, second positive, first negative nitrogen spectral system and NO spectral systems were observed in measured spectra. The band head intensities of these bands have been studied in the dependencies on experimental conditions. Simultaneously, the relative vibrational populations on the given nitrogen states have been calculated. Two discharge tubes made from different materials (PYREX glass and QUARTZ glass) were used in the case of nitrogen plasma containing low oxygen traces (up to 0.2 %). These experiments have been carried out at two wall temperatures for the determination of the temperature effect on the post-discharge. The discharge tube around the observation point was kept at the ambient temperature (300 K) or it was cooled down to 77 K by liquid nitrogen vapor. The total gas pressure of 1 000 Pa and the discharge current of 200 mA were conserved for all these experiments. The relative populations of electronic states were calculated in the dependence on the post-discharge time. The dependencies on oxygen concentration were given, too. The results showed no simple dependence of vibrational populations on oxygen concentration. Generally, slight increase of neutral nitrogen states populations was observed with the increase of oxygen concentration. These observations were well visible due to the intensity of nitrogen pink afterglow effect that was well visible at all oxygen concentrations. The pink afterglow maximal intensity was reached at about 5–10 ms at the wall temperature of 300 K in the PYREX tube. The molecular ion emission was strongly quenched by the oxygen and as this was dominant process for the pink afterglow emission the pink afterglow effect disappears at oxygen concentration of about 2000 ppm. The temperature and wall material influences were observed, too. The post-discharge in nitrogen argon mixtures was studied only in the PYREX tube at the ambient wall temperature of 300 K. The power dissipated in an active discharge was constant of 290 kW. The experimental studies had two new parameters – total gas pressure (500 Pa – 5 000 Pa) and the argon concentrations that were varied in the range of 0–83 %. Also in this case the dependencies of relative intensities of the bands given above were obtained and further the relative populations of electronic states as a function of decay time, total gas pressure and on argon concentration were obtained. The pink afterglow effect was observed at all applied discharge powers and total gas pressures. At the highest argon concentrations, especially at lower pressure, the pink afterglow effect disappeared. The presented experimental work is one of the hugest sets of experiments in the nitrogen with oxygen traces and in nitrogen-argon mixtures. These data can be used as a very good fundament for the further studies using wide numeric modeling of the post-discharge kinetic processes.
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Study of post-discharge kinetic processes by titration methods
Josiek, Stanislav ; Kozáková, Zdenka (referee) ; Mazánková, Věra (advisor)
Many experimental and theoretical works on plasma post-discharges have been published during the last more than fifty years. A part of these works was focused in details on nitrogen discharges and post-discharges and kinetic processes in it. The aim of the presented bachelor`s thesis was to study kinetic processes in post-discharge in pure nitrogen and nitrogen contained methane traces. Atomic nitrogen concentration at different methane concentrations was measured by the nitrogen monoxide titration into the post-discharge. All experimental results were obtained by the optical emission spectroscopy. Optical emission spectra were taken in the range of 300-600 nm. DC discharge was created in a quartz tube in a flowing regime. The flowing regime was chosen for this experiment because of better time resolution of the post-discharge. Nitrogen flow was 400 mln/min. Nitrogen oxide flow was in the range of 0-10 mln/min and it was added at the selected post-discharge time. Experiments were carried out for pure nitrogen and for four different methane concentrations – 0.006, 0.013, 0.019 and 0.025 %. Total gas pressure of 1000 Pa, discharge current of 150 mA and voltage of 1110 V were constant during all these experiments. Nitrogen first positive, second positive and first negative spectral systems, NO spectral system and NO2* spectral system were recognized in all measured spectra. The atomic nitrogen concentration was determined using NO and NO2* intensities, and it was increased by the increase of methane concentration. On the other hand, the nitrogen molecular ion emission was strongly quenched even at very low concentration of methane. From this point of view, this thesis is innovative and brings new results into the worldwide research.
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