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High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes)

An International Journal

ISSN for PRINT: 1093-3611

Institutional price:	$604.00
Issues per year:	4

Best Paper Award Selection - Editorial Board Site

2007, Volume11

149 pages

DOI: 10.1615/HighTempMatProc.v11.i2

Issue price - $168.00

OSCILLATIONS IN DC PLASMA JET AT REDUCED PRESSURES

Vladimir Kopecky
Thermal Plasma Department, Institute of Plasma Physics AS CR, Za Slovankou 3, 18200, Praha 8, Czech Republic

Milan Hrabovsky
Thermal Plasma Department, Institute of Plasma Physics, Za Slovankou 3, 18200, Praha 8, Czech Republic

ABSTRACT

The oscillations of dc plasma jet generated by the hybrid water/argon plasma torch with external anode were studied at different ambient pressures. Fluctuations of plasma radiation from jet were recorded using system of photo-diodes with high frequency response. The frequency and the phase velocity of plasma flow oscillations were determined for various arc currents and argon flows and various ambient pressures. Two main types of oscillations were observed. The first type of perturbations is connected with a movement of an anode attachment and the second type of oscillations arises from plasma boundary instability. Frequencies of this two types oscillations approach each other when the pressure is reduced and the expansion zone was formed. In this case frequencies of these oscillations were equal to 200−350 kHz and their phase velocities were close to thousand meters per second.