Study on generation characteristics of plasma jets of multi-electrode in a pulse vacuum discharge

Active galactic nuclei come in many varieties. A minority of them are radio-loud, and exhibit two opposite prominent plasma jets extending from the proximity of the supermassive black hole up to megaparsec distances. When one of the relativistic jets is oriented closely to the line of sight, its emission is Doppler beamed and these objects show extreme variability properties at all wavelengths. These are called “blazars”. The unpredictable blazar variability, occurring on a continuous range of time-scales, from minutes to years, is most effectively investigated in a multi-wavelength context. Ground-based and space observations together contribute to give us a comprehensive picture of the blazar emission properties from the radio to the γ-ray band. Moreover, in recent years, a lot of effort has been devoted to the observation and analysis of the blazar polarimetric radio and optical behaviour, showing strong variability of both the polarisation degree and angle. The Whole Earth Blazar Telescope (WEBT) Collaboration, involving many tens of astronomers all around the globe, has been monitoring several blazars since 1997. The results of the corresponding data analysis have contributed to the understanding of the blazar phenomenon, particularly stressing the viability of a geometrical interpretation of the blazar variability. We review here the most significant polarimetric results achieved in the WEBT studies.

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Study of formation mechanism of double metal plasma jets in a low-current pulsed vacuum arc discharge

Physics of Fluids ◽

10.1063/5.0037964 ◽

2021 ◽

Vol 33 (3) ◽

pp. 037103

Author(s):

Jia Tian ◽

Wenzheng Liu ◽

Wenjun Zhang ◽

Xitao Jiang

Keyword(s):

Formation Mechanism ◽

Arc Discharge ◽

Plasma Jets ◽

Vacuum Arc ◽

Metal Plasma

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High-Speed Video Analysis of the Process Stability in Plasma Spraying

Journal of Thermal Spray Technology ◽

10.1007/s11666-021-01159-1 ◽

2021 ◽

Author(s):

K. Bobzin ◽

M. Öte ◽

M. A. Knoch ◽

I. Alkhasli ◽

H. Heinemann

Keyword(s):

Plasma Spraying ◽

High Speed ◽

Plasma Jet ◽

Plasma Jets ◽

Time Dependent ◽

Acquisition Time ◽

Fast Fourier Transformation ◽

Frequency Spectra ◽

Dependent Signal ◽

The Stability

AbstractIn plasma spraying, instabilities and fluctuations of the plasma jet have a significant influence on the particle in-flight temperatures and velocities, thus affecting the coating properties. This work introduces a new method to analyze the stability of plasma jets using high-speed videography. An approach is presented, which digitally examines the images to determine the size of the plasma jet core. By correlating this jet size with the acquisition time, a time-dependent signal of the plasma jet size is generated. In order to evaluate the stability of the plasma jet, this signal is analyzed by calculating its coefficient of variation cv. The method is validated by measuring the known difference in stability between a single-cathode and a cascaded multi-cathode plasma generator. For this purpose, a design of experiment, covering a variety of parameters, is conducted. To identify the cause of the plasma jet fluctuations, the frequency spectra are obtained and subsequently interpreted by means of the fast Fourier transformation. To quantify the significance of the fluctuations on the particle in-flight properties, a new single numerical parameter is introduced. This parameter is based on the fraction of the time-dependent signal of the plasma jet in the relevant frequency range.

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Properties of DBD Plasma Jets Using Powered Electrode With and Without Contact With the Plasma

IEEE Transactions on Plasma Science ◽

10.1109/tps.2021.3067159 ◽

2021 ◽

pp. 1-9

Author(s):

Fellype do Nascimento ◽

Konstantin Georgiev Kostov ◽

Munemasa Machida ◽

Alexander Flacker

Keyword(s):

Plasma Jets ◽

Dbd Plasma

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Tiny Cold Atmospheric Plasma Jet for Biomedical Applications

Processes ◽

10.3390/pr9020249 ◽

2021 ◽

Vol 9 (2) ◽

pp. 249

Author(s):

Zhitong Chen ◽

Richard Obenchain ◽

Richard E. Wirz

Keyword(s):

Biomedical Applications ◽

Plasma Jet ◽

Discharge Voltage ◽

Plasma Jets ◽

Atmospheric Plasma ◽

Physical Parameters ◽

Cold Atmospheric Plasma ◽

Water Metal ◽

Plasma Probe ◽

Jet Nozzle

Conventional plasma jets for biomedical applications tend to have several drawbacks, such as high voltages, high gas delivery, large plasma probe volume, and the formation of discharge within the organ. Therefore, it is challenging to employ these jets inside a living organism’s body. Thus, we developed a single-electrode tiny plasma jet and evaluated its use for clinical biomedical applications. We investigated the effect of voltage input and flow rate on the jet length and studied the physical parameters of the plasma jet, including discharge voltage, average gas and subject temperature, and optical emissions via spectroscopy (OES). The interactions between the tiny plasma jet and five subjects (de-ionized (DI) water, metal, cardboard, pork belly, and pork muscle) were studied at distances of 10 mm and 15 mm from the jet nozzle. The results showed that the tiny plasma jet caused no damage or burning of tissues, and the ROS/RNS (reactive oxygen/nitrogen species) intensity increased when the distance was lowered from 15 mm to 10 mm. These initial observations establish the tiny plasma jet device as a potentially useful tool in clinical biomedical applications.

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