Hollow Anode Research Articles

Characteristics of the Hollow Anode Ion-Electron Source

A new type of ion-electron source based on a hollow anode discharge is presented. In such a type of discharge the maximum plasma density is localized at the exit aperture. Constant hydrogen ion current in excess of 1 mA has been obtained with the 1 mm diam. exit aperture and the extraction voltage of 3 kV.

The Effect of Gas on the Development of a Vaccum Arc with a Hollow Anode

The paper describes the results of a study of the formation of a low-pressure space arc with an igniting device and a large-size hollow anode. It is shown that the time of arc formation tf is determined by the dimensions of the hollow anode, the type of gas, and the gas pressure. As the pressure is increased from 4x10-3 to 4x10-2 Pa, tf decreases considerably and the effect of the gas type (air, Ar, Kr, Xe) on tf strengthens; lower tf values corresponding to greater gas atomic masses. On using a 1.5 kA arc in a mesh plasma emitter, 1 kA, (0.6x0.15) m2, electron beams are obtained at 200 kV accelerating voltage and 5xl0-6 s pulse duration.

Cylindrical hollow-anode discharge

Hollow-anode discharge represents a new type of discharge which is realized in a diode consisting of a cylindrical cathode and special type of hollow anode whose inner surface only is conductive. The cylindrical cathode focuses electrons toward the hollow anode placed in the center of curvature, increasing the density of high-energy electrons and efficiency of excitation and ionization in the hollow aperture of the anode. Optical spectrum consists of intense ion lines of the operating gas without anode or cathode material lines.

Hollow anode ion–electron source

A new type of ion–electron source, based on a gas discharge in a diode with concave cathode and a special type of hollow anode, is presented. In this type of discharge, the maximum plasma density is localized at the exit aperture. Constant hydrogen ion currents in excess of 1 mA have been obtained with a 1-mm-diam exit aperture and an extraction voltage of 3 kV. The power supplied to the source, whose volume is less than 0.5 cm3, is only a few watts.

Spectroscopy of hollow anode discharge

Hollow anode discharge represents a new type of discharge which is realized in a diode consisting of a concave cathode and a special type of hollow anode whose inner surface only is conductive. The concave cathode focuses electrons toward the hollow anode, increasing the density of high energy electrons and the efficiency of excitation and ionization in the hollow anode. The optical spectrum, which consists of ion lines only, indicates that in the hollow anode a highly ionized plasma is obtained. The spectrum does not consist of cathode (or anode) material lines.

Performance of a Vacuum Arc Commutating Switch for a Fault-Current Limiter

A vacuum arc device with a hollow cylindrical anode and a button cathode located axially at the bottom of the anode has been evaluated theoretically and experimentally for use in a fault-current limiter as a commutating switch with an applied axial magnetic field. An optimally designed commutating switch of this type should meet the following conditions: 1) inductance of the parallel capacitor should be minimized, 2) time rate of increase for the applied magnetic field should be within an optimum range, 3) a slot in the anode is needed to provide for fast penetration of the magnetic field into the interelectrode region, and 4) anode size (radius and height) should be large enough to give a particle density and a commutation voltage of suitable magnitude for the duty expected.

Detection of x rays from the anode of a vacuum arc

A vacuum arc with hollow cylindrical anode can generate an arc voltage in excess of 10 000 V with currents in excess of 1000 A. A model has been developed that describes this high arc voltage as being caused by the conduction of the current through an electron space-charge region near the anode. The detection of x rays emitted from the anode at the time of the high arc voltage has confirmed the model of this vacuum arc. An x-ray pinhole camera gave spatial resolution and showed that the x rays were emitted from the anode. A p-i-n diode x-ray detector gave temporal resolution and showed that the x rays were emitted during the high arc voltage mode. A lithium fluoride crystal spectrometer gave energy resolution and showed that the emitted x rays were characteristic of the copper anode. This experiment confirmed that the major energy dissipation mechanism for this arc during the high voltage mode was the bombardment of the anode by electrons.

Topography of ion-etched Corning 7059 glass

Topographs of Corning 7059 glass, developed by 7Kv, 70μA Ar+ irradiation from a hollow anode ion gun were investigated. Two forms of surface topography were observed: lens-shaped cavities and waves. These are discussed in terms of measured sputtering yield against incidence angle relation or beam divergence. Practical applications in specimen preparation for transmission electron microscopy and glass homogeneity testing are suggested.

Deposition of crystals from the plasmas of ZrO2, HfO2, ThO2, and CeO2

Deposition occurs onto a cathode from an oxide plasma generated inside a hollow oxide anode by the mechanism called the electrolysis of plasma. The temperature of the cathode is usually over 2000 °C during deposition. Deposits attain fairly large crystalline sizes (about 0.3 mm) in spite of their high deposition rates. And besides, some unusual crystals are formed. For the deposition from ZrO2, HfO2, and ThO2 plasmas, the deposition rate, growth rate, and the current efficiency increase with the plasma current (0.4–8 A) and with feeding O2 gas into the plasmas. On the other hand, heating a cathode externally or feeding Ar gas into them leads to the reduction of those rates, the current efficiency, and yield. The maximum growth rate from the ThO2 plasma is 8.4 μm/sec. Yields exceed 90% in general. Mass-spectrometric analyses showed that the main depositing ion species is ZrO+ for the deposition from the ZrO2 plasma. Deposits obtained are usually black oxides, whose O/M (M=Zr, Hf, and Th) ratios are 1.95, 1.95, and 1.64, respectively. The deposits from ZrO2, HfO2, and ThO2 plasmas are monoclinic ZrO2 with precipitates of metallic α-Zr, monoclinic HfO2 with a small amount of unknown hexagonal crystals (whose lattice parameters are a=3.17 and c=5.02 Å), and a mixture of fcc ThO2 and Th, respectively. When O2 gas is fed into those plasmas, transparent oxide crystals of stoichiometric composition are formed. The deposits from a CeO2 plasma are the black oxides whose O/Ce ratios are 1.53 on the average. Contrary to the phase diagram of the Ce-O system, they show x-ray structures of fcc crystals whose lattice parameter varies from 5.506 to 5.411 Å.

Emission Spectrographic Analysis of Surfaces with an Ion-Sputtering Source

An ion-sputtering source was installed and evaluated as an emission spectrographic source for the analysis of metal surfaces and for the determination of in-depth concentration profiles. This source generates a direct current glow discharge in a low-pressure argon atmosphere between a hollow stainless-steel anode and the sample (the cathode) and sputters material at a controlled rate from the sample surface. The resultant spectrum of the sputtered material is recorded photographically, and the analysis is completed by conventional spectrographic techniques. The power supply of the source can be operated in either a constant dc mode or a square-wave dc mode, but better repeatability and accuracy have been achieved with the square-wave dc mode. Before any significant sputtering occurs with this source, the voltage must exceed 240 Volts, the threshold sputtering voltage. The sputtering rate increases with both source current and voltage. This source has been used for the quantitative analysis of the surface of steel products and the determination of changes in composition with depth below the surface.

On the influence of reflection of electrons on colt-ampere characteristics of high-voltage glow discharge with hollow anode: Ya Y Udris et al,Zh Tekh Fiz, 44 (1), 1974, 213–215 ( in Russian)

On the influence of reflection of electrons on colt-ampere characteristics of high-voltage glow discharge with hollow anode: Ya Y Udris et al,Zh Tekh Fiz, 44 (1), 1974, 213–215 ( in Russian)

An electrostatic electron energy analyser for 3-20 keV electrons

An electrostatic energy analyser has been developed to determine the energy spectra of electrons present in 1-10 mA beams from hollow anode gas discharge guns, operating between 3-20 kV. Basically the instrument employs the electrostatic field between charged, concentric cylinders to achieve dispersion.

Messungen der radialen Verteilungen von elektrischer Stromdichte und Temperatur im Wasserstofflichtbogen mit axialem Magnetfeld

Abstract The radial distribution of the axial electric current density in a stationary hydrogen arc with axial magnetic field was measured. This was done by shooting small induction coil probes across the arc. The experiments confirmed that the arc current is almost completely restricted to the magnetic flux tube defined by the cathode radius, as discussed in a previous paper. In the case of a hollow anode a distinctly tube-like current density distribution was found. With the aid of the axial electric field measurements already presented temperature profiles in good agreement with other experimental methods were derived. In addition, the ohmic heat input into the arc could be determined. This is much larger than the energy that can be lost radially as a result of thermal conduction according to the measured temperature profile and the thermal conductivity known from the theory. The cause may be the Rayleigh-Taylor instabilities which were observed or radial mass flows directed outwards. Allowing for even relatively slow flows (υr ˂ 104 cm/sec) in the calculations one obtains good agreement with the measured distributions.

Messungen der radialen Verteilung der elektrischen Feldstärke im Wasserstofflichtbogen mit axialem Magnetfeld

Abstract In a stationary hydrogen arc with axial magnetic field the radial distribution of the axial electric field Ez was measured by shooting a double potential probe across the arc. It was found that Ez strongly decreases outside the magnetic flux tube defined by the cathode radius and tends to zero. The measured distribution of Ez agrees qualitatively with computations allowing for the observed rotation profile. In a very fast rotating arc with a hollow anode Ez was found to vanish not only outwards, but also towards the axis, as predicted by the theory.

Experimentelle Untersuchung der Rayleigh-Taylor-Instabilität eines rotierenden Wasserstoff-Lichtbogens im axialen Magnetfeld

Abstract A hydrogen arc with a hollow anode in an axial magnetic field is subjected to Rayleigh-Taylor instabilities as a result of rotation due to the radial current components at the anode. These instabilities take the form of periodic fluctuations in the light intensity emitted from the boundary regions of the arc. The modes m = 4 to m = 7 which occur in succession with increasing magnetic field are identified by measuring the signal phases in end-on observation of the arc. The rotational velocity of the arc plasma is determined spectroscopically and comparison is made with the non-dissipative MHD theory, which yields growth rates ∼ .The deviations from this theory that were observed in this experiment are ascribed to dissipative effects.

Design and Analysis of a High Brightness Axial Flash lamp

A high color temperature, pulsed axial flashlamp which is very simple to build is described. The radiation is produced in argon or helium gas which is contained in an alumina tube at atmospheric pressureand allowed to flow out into the atmosphere through a hollow anode. At current densities of 40 kA/cm(2) (in a 1.5 cm(2) bore) the helium plasma radiates like a 30,000 K blackbody and can produce about one W/ angstrom of uv radiation in a f/8 solid angle. The voltage vs current relation of the arc discharge is ofthe form upsilon = K(0)|i|((1/2)) which allows one to design an R, L, C series discharge circuit which can produce a critically damped current pulse of arbitrary length.

Sintering in Gas Discharges

THE application of gas-phase glow discharges to the activation of many chemical reactions is becoming increasingly important but the parallel application to various aspects of the processing of materials is not as yet so well known. Dugdale1 has described the mechanism and characteristics of the d.c. glow discharge and particular applications to both hollow cathode and hollow anode glow discharge heaters, which can be used for processes requiring an intense heat flux such as zone refining and evaporation machining.

Measurements of plasma rotation in a hollow cathode discharge

The plasma column of a hollow cathode, hollow anode vacuum arc is found to rotate in the direction of the ion gyro motion with velocities of several times 105 cm/sec. The maximum velocity is reached when the magnetic field strength is increased to a characteristic value (ωcτ ≈ 1); it then decreases gradually at higher field strengths. The measurements were made with a small pendulum hanging above the arc and were confirmed spectroscopically. The experimental results are described by the equation of motion of the ions with the electrons being able to move practically unhindered by the magnetic field, as was suggested before for the explanation of diffusion measurements. Changing parameters - such as ion mass, neutral gas density and radial electrical field - makes the value of the characteristic magnetic field strength for maximum velocity shift in the expected direction. The radial particle flux is, however, found to be smaller than that expected from the collisional diffusion theory of Simon (1955). Thus one has to assume that the azimuthal velocity of the ions is controlled by a much higher effective collision frequency than their radial diffusion current. It is suggested that this result is related to density perturbations of high energy (e/kTe 1) found to be propagating in the direction of the electron gyro motion with a frequency near the drift frequency.

1670. Some properties of high voltage glow discharge in a hollow anode: Ya Ya Udris et al,Zh Tekh Fiz,36(6), June 1966, 1140–1173 (in Russian)

1670. Some properties of high voltage glow discharge in a hollow anode: Ya Ya Udris et al,Zh Tekh Fiz,36(6), June 1966, 1140–1173 (in Russian)

Combined Anode-Cathode Feed of a Hollow-Cathode Arc

A simple recipe is given for separating the anode and cathode regions of a hollow-cathode-arc plasma by a baffle and introducing a small gas feed through the hollow anode. By this stratagem, the anode-region plasma can be tailored within wide limits for ion species and density, and degree of ionization. For example, a 95% pure hydrogen plasma with ion density 1013–1014 cm−3, 90% ionized, can be produced at low voltage, with the cathode running under ideal conditions in argon.