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Plasma-jet systems - experiment and model
Rubovič, Peter ; Kudrna, Pavel (advisor) ; Hubička, Zdeněk (referee)
In the present work we study the ow of working gas through a plasmajet system. In this work we describe the basic principle of hollow cathode discharge and its use for technological applications, mainly for thin layers coating. One of the important parameters during the deposition is the speed of the working gas ow and with it the sputtered target material towards the substrate. Because of the reproducibility and precision of the experiments it is important to know the relation between the working gas ow and external parameters of the experiment, e.g. ow of the gas and the pressure in the chamber. This is the reason why measurements of ions velocity using Langmuire electrostatic probe and pulse regime of plasmajet were done. Measured data are compared with a computer model, which was developed in this work. This model describes the ow of the working gas by solving Navier-Stokes equation for compressible Newtonian uids. The results of this model are compared with results from the paper describing the ow through the hollow cathode. It shows good agreement inside the cathode. The model is giving dierent results when comparing to measured data which are from the area outside the cathode. Part of the model description is a discussion of the temperature dependence of the ow.
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Discharge plasma sources supported by magnetic field
Kolpaková, Anna ; Kudrna, Pavel (advisor) ; Marek, Aleš (referee)
This work concerns the low-temperature plasma diagnostic in the dcdischarge in the cylindrical magnetron in argon. For measurements Langmuir and emissive probes were used. The aim of this diploma work was the diagnostics of the radial plasma parameters especially with the improved construction of the emissive probe and the verification of it's use for the determination of the plasma potential. The work was also focused on the influence of the angle between the emissive probe loop and the magnetic field to the emissive probe data. In the experimental part the cylindrical magnetron system, the construction of Langmuir and emissive probes and the probe circuit are described. After that the software for the data acquisition created using Agilent VEE programming language and evaluation of probe data is explained. Probe characteristics were measured by the Langmuir probe in the dependence on the radial position. In such way the radial profiles of the plasma potential, floating potential and electron density were determined. Measurements were performed at different values of the pressure, magnetic field and the discharge current. The floating potential of the strongly emitting probe was used to measure the plasma potential at different magnetic field strengths.
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Influence of the laser mixture composition on the existence of the dinitrogen bands
Morávek, Matěj Jan ; Hrachová, Věra (advisor) ; Kudrna, Pavel (referee)
This project studies mixtures of helium, nitrogen and carbon dioxid, widely used in so called CO2 lasers. These lasers are classified as discharge lasers. In the case of low output lasers is often used a DC glow discharge. We can find bands so called first and second positive systems of a dinitrogen molecule in an emission spectrum of the glow discharge. It is possible to deduce energetic balance and a vibrational temperature from these bands. The vibrational temperature was studied by the vibrational spectroscopy of dinitrogen molecule for various discharge currents and pressures and for various distribution of nitrogen in the mixture (we will start with an industrial mixture LASAL 63).
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Magnetic field Supported Discharge Based Plasma Sources
Havlíček, Josef ; Kudrna, Pavel (advisor) ; Tichý, Milan (referee)
Main aim of this work was measurement of a floating potential fluctuations in the cylindrical magnetron in classical configuration in neon. Two Langmuir probes were used for measurement of wave vector. The following values were measured: pressure p in range 1-7 Pa, magnetic induction B in range 10-40 mT, discharge current I in range 5-100 mA, discharge voltage U and floating potential Uf. Fluctuations were described by dependencies of power spectral density on frequency S(f) and by histograms S(k,f), where k is wave vector. Several discharge modes were observed in the magnetron. These are characterized by different values of discharge voltage, electric field in positive column, magnitude of the floating potential etc. The discharge conditions, where peaks were observed in spectra, were determined. Only one peak with frequency in range 4-16 kHz was mostly observed. Most of these peaks had zero wave vector in histogram S(k,f), i.e. the floating potential synchronously oscillated in the whole discharge area. For some discharge conditions histograms with non-zero wave vector for noise background were observed.
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