In this paper, a cold He atmospheric pressure plasma jet that is generated using a dielectric barrier discharge configuration device is presented. This device is equipped with double-grounded ring electrodes that are driven by a sinusoidal excitation voltage. The properties of the cloning of filamentous current are studied. The frequency of the collisions between the ion and the neutral particles is calculated by measuring the current phase difference between the filamentous current and its corresponding clone. The frequency of the collisions between the ion and the neutral particles is of the order of 10 8 Hz.
The properties of a helium atmospheric-pressure plasma jet (APPJ) are diagnosed with a dual assisted grounded electrode dielectric barrier discharge device. In the glow discharge, we captured the current waveforms at the positions of the three grounded rings. From the current waveforms, the time delay between the adjacent positions of the rings is employed to calculate the plasma bullet velocity of the helium APPJ. Moreover, the electron density is deduced from a model combining with the time delay and current intensity, which is about 10 11 cm −3 . In addition, The ion-neutral particles collision frequency in the radial direction is calculated from the current phase difference between two rings, which is on the order of 10 7 Hz. The results are helpful for understanding the basic properties of APPJs.
The measurements of the ion densities in the atmospheric AC barrier corona argon discharge are carried out by receiving and analyzing the frequencies of the electromagnetic radiation emitted from the plasma. An auxiliary excitation source composed of a pin-to-pin discharge system is introduced to excite the oscillations of the main discharge. To analyze the resonance mechanism, a complemented model based on a one-dimensional description of forced vibrations is given. Calculations indicate that Ar þ 2 is the dominant ion ($89% in number density). By analyzing resonance frequencies, the ion densities of Ar þ 2 are in the order of 10 19 $ 10 20 m À3 and increase slowly as the applied voltage increases. V C 2014 AIP Publishing LLC.
Presently one of the most important tendencies is the use of tungsten (W) monoblock material for the first wall and other plasma facing components (PFCs) in tokamak. The use of low Z materials such as B4C for protection of PFCs is a conventional method to decrease heavy impurity influx into tokamak plasma. This study involves the fabrication and characterization of inductively coupled plasma (ICP) thermal sprayed B4C coating on tungsten monoblock. Thickness of the coating was about 120μm. Surface morphology of the coating is presented with scanning electron microscope and metallographic microscope analyses. X-ray diffraction analysis and X-ray photoelectron spectroscopy showed that the main phase and chemical composition of the coatings were preserved when compared with that of the initial B4C powder. Adhesion test result revealed that the adhesion/cohesion strength of the coating was above 13.1 MPa. This work is innovative not only for the ICP thermal sprayed method for the B4C coating fabrication but for the plasma sprayed B4C on tungsten substrate.
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