Spatially resolved temperature measurements in an atmospheric plasma torch using theA2 Σ+,v′ = 0 →X2 Π,v″ = 0 OH band

Kopecki

Gaiser

et al. 2013

Contrib. Plasma Phys.

Microwave plasmas at atmospheric pressure are used for surface treatments like for example cleaning, sterilization or decontamination purposes, for a pre-treatment to increase the adhesion of lacquer, paint, or glue, and for the deposition of different kind of layers and coatings. Micro plasma jets can also be applied for biomedical applications and for treatment of small and complex geometries like for example the inside of capillaries. Larger plasma torches which exhibit higher gas temperatures can also be used for chemical syntheses like waste gas decomposition, methane pyrolysis, or carbon dioxide dissociation and for plasma spraying purposes. In the present publication an overview on the development and the investigation of the operating principle of two atmospheric pressure microwave plasma torches at frequencies of 2.45 GHz and 915 MHz will be presented. The plasma sources are based on a cylindrical resonator combined with coaxial structures. To explain how these plasma sources work, simulations of the electric field distribution will be discussed. Furthermore, some physical characteristics of an air and an Ar/H2 atmospheric plasma like gas temperatures, excitation temperatures and densities as well as the heating of the plasma by the microwave will be investigated.

Section: Experimental Set-ups and Applied Methods For The Characterizmentioning

confidence: 99%

Section: Experimental Set-ups and Applied Methods For The Characterizmentioning

confidence: 99%

Microwave Plasmas at Atmospheric Pressure

Kopecki

Gaiser

et al. 2013

Contrib. Plasma Phys.

“…Therefore, this transition is often used to determine the gas rotational temperature T rot which can be assumed to be the gas temperature T g [45][46][47][48][49] even though this method is challenged by M. Baeva et al [50]. The A 2 Σ + − X 2 Π γ -transition of the free OH radical between 306 nm and 310 nm is very sensitive to temperature, and the quantum mechanical constants are well known for this transition.…”

Section: Applied Spectroscopic Methodsmentioning

confidence: 99%

Spectroscopic Investigation of a Microwave‐Generated Atmospheric Pressure Plasma Torch

Walker

Schulz

et al. 2012

Contrib. Plasma Phys.

The investigated new microwave plasma torch is based on an axially symmetric resonator. Microwaves of a frequency of 2.45 GHz are resonantly fed into this cavity resulting in a sufficiently high electric field to ignite plasma without any additional igniters as well as to maintain stable plasma operation. Optical emission spectroscopy was carried out to characterize a humid air plasma. OH-bands were used to determine the gas rotational temperature Trot while the electron temperature was estimated by a Boltzmann plot of oxygen lines. Maximum temperatures of Trot of about 3600 K and electron temperatures of 5800 K could be measured. The electron density ne was estimated to ne ≈ 3 · 10 20 m −3 by using Saha's equation. Parametric studies in dependence of the gas flow and the supplied microwave power revealed that the maximum temperatures are independent of these parameters. However, the volume of the plasma increases with increasing microwave power and with a decrease of the gas flow. Considerations using collision frequencies, energy transfer times and power coupling provide an explanation of the observed phenomena: The optimal microwave heating is reached for electron-neutral collision frequencies νen being near to the angular frequency of the wave ω.

“…A variation of the microwave power showed that the gas temperature is not increasing with increasing microwave power but the plasma is extended. [5] The two atomic oxygen transitions 5 P 0 ! 5 S at 777.34 nm and 3 S 0 !…”

Section: Characterisation Of the Plasma Using Optical Emission Spectrmentioning

confidence: 99%

Development and Characterisation of a Microwave‐heated Atmospheric Plasma Torch

Plasma Processes & Polymers

Alberts

Kaiser

et al. 2009

Among other applications, microwave plasma sources at atmospheric pressure are used for the decomposition of halogenated volatile organic compounds (VOC). The presented microwave plasma torch is based on an axially symmetric resonator. Simulations of the electric field distribution, Eigen frequency analyses and measurements of the resonant frequency resulted in an improved design. Microwaves of 2.45 GHz are fed into this cavity resulting in a sufficiently high electric field for ignition and maintaining stable plasma. The characterisation of the plasma is made with optical emission spectroscopy. The decomposition of VOC was analysed with FTIR‐spectroscopy, a mass spectrometer and an FID.