Measurement of Plasma Parameters in Low Temperature High Density Hollow Cathode Plasma Jet Working in Magnetic Field (original) (raw)
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Plasma Properties of a Low-Pressure Hollow Cathode DC Discharge
Iraqi Journal of Science
The current study involves an experimental investigation of plasma main parameters of a DC discharge with a hollow cathode (HCD) geometry in air using apertures of different diameters from the hollow cathode (1, 1.5, 2, and 2.5 cm). A tiny Langmuir probe is used to investigate the plasma properties. The HCD was operated at constant power of 12.4 W and gas pressures ranging between 0.1 to 0.8 torr. It was observed that the operational conditions strongly affect the electron temperature and density, while the hollow cathode diameter has not much influence. The main important observation was that at relatively high air pressure (>0.4 torr) two electron temperatures were obtained, while at relatively low pressure (<0.4 torr), a single electron temperature was found. The results showed that the measured electron temperature decreased nearly linearly with increasing gas pressure.
Plasma properties of a DC hollow cathode discharge
2006
We have investigated the plasma properties of a Hollow Cathode Discharge (HCD) using different dimensions of hollow cathode aperture (1 to 8 mm) in argon operating medium. The diagnostic used to investigate the plasma properties is a tiny Langmuir probe. The diameter and length of the Langmuir probe was chosen such that it draws a measurable current from the plasma causing a minimal perturbation to the surrounding plasma and remains rigid within the plasma as well as the cylindrical probe theories are applicable while calculating the electron temperature and plasma density. The probe was placed perpendicular to the axis of the hollow cathode at a distance of 20 mm from the hollow cathode side. The HCD was operated in the voltage range of 600 to 1000 V and pressures range of 70 to 100 mtorr. We observed that electron temperature and density varies with the operational condition. The estimated electron temperature is less than 10 eV and the temperature is maximum in the range of 3 to 5 mm diameter of the hollow cathode and a pressure range of 75 to 85 mTorr. The calculated maximum density is of the order of 10 10 cm -3 .
The properties of low pressure argon pulsed hollow cathode discharge were investigated using Rogoviski coil, and time resolved Optical emission spectroscopy (OES) under different conditions of gas flow rate (20-240 sccm), and at charging voltage 4kv. The Electron temperatures were measured in argon plasmas as a function of time, using the argon line emission intensity ratio of 4675A 0 /4259A 0 and 4348A 0 /4159A 0. Also the electron temperature was determined by adding small admixture of helium gas (5sccm) to the working argon gas without disturbing the plasma properties, using the intensity helium line ratio He 4713A 0 /4921A 0 and 5048A 0 /4713A 0. The electron variation density with time was measured using the line intensity of exited argon ion 4880A 0. The results obtained indicated that the maximum discharge current is approximately 6.7kA. It was found that the electron temperature decreases with the increase of gas flow rate; this is attributed to the increase in the number of collisions between electrons and another plasma species.
Iraqi Journal of Physics (IJP)
Experimental study on the effect of cylindrical hollow cathode, working pressure and magnetic field on spatial glow distribution and the characteristics of plasma produced by dc discharge in Argon gas, were investigated by image analyses for the plume within the plasma. It was found that the emission intensity appears as a periodic structure with many peaks appeared between the electrodes. Increasing the pressure leads to increase the number of intensity peaks finally converted to continuous form at high pressure, especially with applied of magnetic field, i.e. the plasma is more stable with the presence of magnetic field. The emission intensity study of plasma showed that the intensity has a maximum value at 1.07 mbar pressure and decrease with more pressure.
Physics of Plasmas, 2013
Low-temperature, high-pressure plasma jets have an extensive use in medical and biological applications. Much work has been devoted to study these applications while comparatively fewer studies appear to be directed to the discharge itself. In this work, in order to better understand the kind of electrical discharge and the plasma states existing in those devices, a study of the electrical characteristics of a typical plasma jet, operated at atmospheric pressure, using either air or argon, is reported. It is found that the experimentally determined electrical characteristics are consistent with the model of a thermal arc discharge, with a highly collisional cathode sheet. The only exception is the case of argon at the smallest electrode separation studied, around 1 mm in which case the discharge is better modeled as either a non-thermal arc or a high-pressure glow. Also, variations of the electrical behavior at different gas flow rates are interpreted, consistently with the arc model, in terms of the development of fluid turbulence in the external jet. V
Contributions to Plasma Physics, 2002
In the recent decade an RF driven, low-pressure plasma reactor with supersonic plasma jet was developed (RPJ). This reactor was successfully used for deposition of thin films of various materials. The deposition of thin films indicates that the properties of the deposited films are dependent on the sputtering or reactive sputtering processes appearing inside the nozzle (hollow cathode). The nozzle (hollow cathode) fabricated of different kinds of materials and alloys works both as a cathode of the radio frequency (RF) hollow cathode discharge and as a nozzle for plasma jet channel generation as well. The RF hollow cathode discharge is a secondary discharge, which is induced by the primary RF plasma generated in the reactor chamber. The present paper deals with the experimental study of this RF hollow cathode discharge. The stress is laid on the investigation of the axial distribution of discharge parameters and sputtering processes inside the nozzle. On the base of experiments, the simple model of the axial distribution of the investigated RF hollow cathode discharge has been developed.
The Effect Hollow Cathode Depth on Plasma Characteristics
2018
Experimental study on the effect of hollow cathode depth on spatial glow distribution and the characteristics of plasma produced by dc discharge in Argon gas, were investigated bycurrent-voltage characteristic and image analyses for the glows within the plasma. It was found that the increasing the pressure leads to compress the cathode regions while increase the positive column, which appeared with periodic structure. increasing hollow depth from 19 to 40 mm reduce the positive column fluctuation and converted to continuous form at high pressure. The hollow cathode configurationalters the Paschen curves parameters, the emission intensity distribution and the currentpressure curve.
Iraqi Journal of Science
This work is an experimental study about the effects of gas pressure and magnetic field on plasma characteristics produced in an internal hollow electrodes discharge (HED) system. The results show that the breakdown voltage values increase with increasing the working pressure (especially with the presence of a magnetic field). The breakdown voltage depends on the p.d. product, where p is the gas pressure and d is the distance between the electrodes. While the values of current discharge decrease with the increase of the working pressure. The temperature of electron and the number density of electron are calculated from the Boltzmann method and the broadening of Stark, respectively. The results showed that the electron number density ( ) and plasma frequency ( ) increase with increasing the gas pressure, especially with the presence of a magnetic field, i.e. the plasma is more stable with the presence of magnetic field. While the electron temperature ( ) and Debye length ( ) de...
Journal of Applied Physics, 2005
A detailed study of the spatial variation of plasma density, temperature, and potential in hollow cathodes using miniature fast scanning probes has been undertaken in order to better understand the cathode operation and to provide benchmark data for the modeling of the cathode performance and life described in a companion paper. Profiles are obtained throughout the discharge and in the very high-density orifice region by pneumatically driven Langmuir probes, which are inserted directly into the hollow cathode orifice from either the upstream insert region inside the hollow cathode or from the downstream anode-plasma region. A fast transverse-scanning probe is also used to provide radial profiles of the cathode plume as a function of position from the cathode exit. The probes are extremely small to avoid perturbing the plasma; the ceramic tube insulator is 0.05 cm in diameter with a probe tip area of 0.002 cm 2 . A series of current-voltage characteristics are obtained by applying a rapid sawtooth voltage wave form to the probe as it is scanned through the plasma at speeds of up to 2 m / s to produce the profiles with a spatial resolution of about 0.05 cm. At discharge currents of 10-25 A from the 1.5-cm-diameter hollow cathode, the plasma density inside the cathode is found to exceed 10 14 cm −3 , with the peak density occurring upstream of the orifice. The plasma potentials on axis inside the cathode are found to be in the 10-20 V range with electron temperatures of 2 -5 eV, depending on the discharge current and gas flow rate. A potential discontinuity or double layer of less than 10 V is observed in the orifice region, and under certain conditions appears in the bright "plasma ball" in front of the cathode. This structure tends to change location and magnitude with discharge current, gas flow, and orifice size. A potential maximum proposed in the literature to exist in or near the cathode orifice is not observed. Instead, the plasma potential increases from the orifice exit both radially and axially over several centimeters to values of 5 -10 V above the anode voltage. The potential and temperature profiles inside the cathode are insensitive to anode configuration changes that alter the discharge voltage at a given flow. Application of an axial magnetic-field characteristic of the cathode region found in ring-cusp ion thrusters increases the plasma density in the cathode plume, but does not significantly change the potential or temperature. Measurements of the plasma profiles and the internal cathode parameters for a hollow cathode operating at discharge currents of up to 25 A in xenon are shown and discussed.