Pavel Slavíček

The high pressure torch discharge plasma source

We present a plasma source which works on the principle of the arc torch discharge. The powered electrode of the arc torch discharge was made from a thin pipe that simultaneously acts as the nozzle through which the working gas flows to the discharge region. The flow of the working gas stabilizes the arc torch discharge and a well defined plasma channel is created. The advantage of this system is that it is able to work at high pressure of working gas up to atmospheric pressure inside the plasma-chemical reactor and also in free space.

Planar UV excilamp excited by a surface barrier discharge

In the contribution, typical characteristics of planar excilamp based on KrCl* and XeCl* exciplex molecules are presented. The excitation of working mixture Kr/Xe/Cl2 is realized by means of the surface barrier discharge at pressures of 0.1 - 1 bars. They were measured and discussed spectra emitted by the plasma in UV/VIS/NIR spectral range, intensity of emitted light vs. total pressure in the discharge and a composition of the working mixture, power of emitted light, resp. The radiation power vs. input electric power, space distribution of emitted light including basic electrical parameters of the discharge were also measured. It was shown that characteristic power of UV radiation emitted in the spectral range 200 - 400 nm is about 6 mW/cm2 while the efficiency could be about 8 %.

Formation of aluminium, aluminium nitride and nitrogen clusters via laser ablation of nano aluminium nitride. Laser desorption ionisation and matrix‐assisted laser desorption ionisation time‐of‐flight mass spectrometry

Laser Desorption Ionisation (LDI) and Matrix-Assisted Laser Desorption Ionisation (MALDI) Time-of-Flight Mass Spectrometry (TOFMS) were used to study the pulsed laser ablation of aluminium nitride (AlN) nano powder. The formation of Al(m)(+) (m=1-3), N(n)(+) (n=4, 5), AlN(n)(+) (n=1-5, 19, 21), Al(m)N(+) (m=2-3), Al(3)N(2)(+), Al(9)N(n)(+) (n=5, 7, 9, 11 and 15), Al(11)N(n)(+) (n=4, 6, 10, 12, 19, 21, 23, and 25), and Al(13)N(n)(+) (n=25, 31, 32, 33, 34, 35, and 36) clusters was detected in positive ion mode. Similarly, Al(m)(-) (m=1-3), AlN(n)(-) (n=1-3, 5), Al(m)N(-) (n=2, 3), Al(2)N(n)(-) (n=2-4, 28, 30), N(n)(-) (n=2, 3), Al(4)N(7)(-) Al(8)N(n)(-) (n=1-6), and Al(13)N(n)(-) (n=9, 18, 20, 22, 24, 26, 28, 33, 35, 37, 39, 41 and 43) clusters were observed in negative ion mode. The formation of the stoichiometric Al(10) N(10) cluster was shown to be of low abundance. On the contrary, the laser ablation of nano-AlN led mainly to the formation of nitrogen-rich Al(m)N(n) clusters in both negative and positive ion mode. The stoichiometry of the Al(m)N(n) clusters was determined via isotopic envelope analysis and computer modelling.

Plasma pencil as an excitation source for atomic emission spectrometry

A 13.56 MHz plasma jet discharge, called a plasma pencil, was investigated. Rotational and excitation temperatures, and electron number densities for the pencil under and without sample load were calculated using OH band spectra, Ar lines and Hβ line, respectively. The rotational temperatures were found to be relatively low at about 800 K, however, excitation temperatures exceeded 4000 K. The plasma was found to be strongly non-isothermal. Some atomic lines of elements were easily observed. Aqueous solution-based aerosols were incorporated into the plasma without desolvation. Standard water solutions of the elements were nebulized into the plasma. The Ar carrier gas and Ar plasma gas flow rates were 0.3 and 4.0 l min−1, respectively. The forwarded power was 140 W. Intensities of the atomic lines, temperatures and electron number densities along the discharge tube were acquired in different positions from the aerosol entrance and an optimal position providing the best signal-to-noise ratio for each line intensity was established. Calibration dependencies for Ca, Cu, Mg, Zn, Li, Na were measured in the rage of 1–100 mg l−1. 3-sigma detection limits in the best observation axial position were (μg l−1): 27 (Ca), 49 (Cu), 58 (Mg), 40 (Li), 13 (Na) and 180 (Zn).

Diagnostics and Applications of High Frequency Plasma Pencil

The so called high frequency plasma pencil is a source of highly active environment (electrons, ions, reactive radicals, excited atoms, and molecules) which can be generated at atmospheric, reduced or increased pressure, preserving a good control of the performance. The discharge can be either unipolar or bipolar. The properties of unipolar atmospheric pressure discharges are discussed on the basis of simple theoretical considerations and electric probe measurements. The plasma pencil discharge is studied by optical emission spectroscopy in the gas phase at atmospheric pressure as well as immersed in liquid using argon as a working gas. From the emission spectra the electron, vibrational and rotational temperatures are calculated for various distances from the plasma pencil electrode. Several technological applications like restoration of archaeological glass and metal artifacts, fragmentation of molecules for microelectrophoresis and plasma polymerization are summarized. An advantage of the plasma pencil is that it can be easily operated and controlled.

RF discharges at atmospheric pressure

The described plasma source is based on the RF torch discharge. The powered RF electrode of the torch discharge plasma source is made from the thin metal pipe with an inner diameter of 1–2 mm and with a length of several cm. The working gas (argon pure or with an admixture of reactive components) flows through the RF electrode as the nozzle. The electrode is connected through the matching unit to the RF generator of the frequency of 13.56 MHz.The advantage of this described plasma source consists in the fact that the torch discharge remains stable up to the atmospherical pressure of the working gas even in the liquid environments. Up to now the torch discharge has been used only for treatment in liquid environment only for archaeological artefacts. For further applications it is necessary to additional study of this phenomenon. While in previous papers we presented a measurement of different temperatures from spectra emitted by plasma, there is drawn attention to equiintensity maps inside the nozzle.

Deposition of polymer films by rf discharge at atmospheric pressure

In this contribution we report some typical properties of the discharge which has been used for deposition of thin films and some mechanical parameters of thin films. RF plasma nozzle can burn very well even at atmospheric pressure. Special properties of RF discharges offer hopeful technological applications like deposition of thin solid films. The knowledge of physical parameters of plasma has been required. The parameters of the plasma were investigated by spectral and optical methods. The powered RF electrode of the torch discharge plasma source is made from the metal or dielectric pipe with an inner diameter of 1÷2 mm and with a length of several centimeters. The electrode is connected through the matching unit to the RF generator driven at the frequency of 13.56 MHz. The mixture of argon andn-hexane or HMDSO (hexamethyldisiloxane, C6H18Si2O) gas flows through the RF electrode at the pipe Fig. 1. Polymer films were deposited on the several substrates e.g. glass, brass polished plates and Si wafers.

Plasma-liquid technologies for treatment of archaelogical artifacts

Plasma-liquid technologies at atmospheric pressure provide a wide range of possibilities for applications. One of them, the treatment of archaeological artifacts, is presented in this paper. The effects of discharges between a metal electrode and a solution surface and/or an interaction of hollow cathode plasma jet, plasma pencil, with liquid on the corroded surface of bronze and glass artifacts were studied. It was compared with standard low pressure plasma techniques and with the effects of electrolysis. Original and treated objects were characterized by means of scanning electron microscope (SEM) with energy dispersive analyser used for the spot elemental analyses.

ENERGY EFFICIENCY OF PLANAR DISCHARGE FOR INDUSTRIAL APPLICATIONS

Diffuse Coplanar Surface Barrier Discharge has proven its capabilities as an industry-ready plasma source for fast, in-line and efficient plasma treatment at atmospheric pressure. One parameter required by industry is energy efficiency of the device. In this paper, we present the energy efficiency of the whole plasma system, and we investigate possible sources of errors.

Plasma pencil — A new small scale source for atmospheric surface modifications

Plasma pencil is a device which can produce plasma jet at atmospheric pressure and low power (10–200 W) from DC to HF. The jet character of the plasma makes this device very efficient in aimed local (1 – 102 mm2) modifications of surfaces. Great variability in possible power sources allow to achieve a broad range of effects on materials. We have tested bipolar discharges with a metal object and a unipolar HF discharge to burn the glazing on ceramics. Both technologies could be prospective.