Argon Gas Discharge Research Articles

The modelling of a discharge sustained by a standing surface wave

Presents a model of a microwave discharge sustained by a standing surface wave. An experimental verification of the model is made by carrying out a discharge in argon gas. The model is based on the solution of an electron diffusion equation in a gas, assuming that electrons are the sole particles causing the ionisation of gas, disappearing on the walls of the discharge tube during the process of recombination. The calculated and experimentally determined values of the axial distribution of electron density, the intensities of electric and magnetic fields and the axial distribution of intensities of neutral and ion lines are compared. This comparison shows good agreement of the model with the experiment.

Kinetic theory of the high-frequency part of the slow electromagnetic mode in weakly ionized gas-discharge argon plasma with inelastic collisions

The spectral characteristics of the high-frequency part of the slow electromagnetic mode, specific for plasmas placed in an external d.c. electric field, as well as the features of the corresponding instability, are analysed for weakly ionized argon gas-discharge plasmas with E/n ranging from 25 to 150 Td, and with electron temperatures between 60000 and 70000 K. The analysis is based on the linear theory of perturbation, and the dynamics of the electrons is described by appropriately modified kinetic equations for the one-particle distribution function. Attention is focused on the collisional processes between electrons and neutrals, and both elastic and excitational collisions are taken into account. Apart from the ‘indirect’ collision effects (modifications of the form of the electron steady-state distribution function, evaluated here analytically, with the thermal motion of the neutrals included), their ‘direct’ influence (arising from perturbations of the collision integrals) is also significant in the electron temperature range considered. As a consequence of the ‘direct’ influence of inelastic collisions, in particular, the mode studied was found to exist in two distinctly separate wavelength ranges. The instability was found to develop only in the one corresponding to shorter wavelengths (below some 30 cm).

Emission Properties of Electrodeless Argon Gas Discharge in VUV Region

The dependences of the VUV light intensity from an electrodeless Argon gas discharge on various parameters such as the gas pressure, gas flow rate, input voltage, input current and discharge current were investigated. These data can be utilized in designing this type of VUV light source. The peak intensity of the light in the 50 to 110 nm wavelength region was estimated to be about 1.8×10-4 W/cm2 at the output aperture of the discharge tube.

Lokale Diagnostik einer Argon‐Niederdruckentladung mit Hilfe der resonanten Laserstreuung

AbstractWe report on the experimental investigations on a laser‐like low pressure argon gas discharge. The discharge parameters varied in the range from 0,05 to 1 Torr for the gas pressure and from 10 to 30 A for the discharge current.Local electron densities and temperatures have been measured with an adjustable spherical probe.Spatially resolved measurements of the temperatures and drift velocities of the Ar+‐ions in the radial and axial direction of the positive column have been carried out by the resonant laser light scattering (fluorescence technique).The radial density profiles of the excited Ar+‐ions have been determined in two different ways and have been compared with the calculations based on a simple collisional radiative model.

Electron swarm characteristics in an argon discharge

A numerical study is applied to the argon gas discharge by solving Boltzmann's equation with other two limiting conditions. The gas parameters are obtained and compared with available experimental and theoretical data. The study suggests that at moderate values of E/P, i.e. less than 30 V cm-1 Torr-1, a little more than one half of the total excitation energy, and at higher values of E/P about 0.3 of it, is expended in the excitation of the metastable states by the electron collisions in the gas.

The hollow cathode as a source for diatomic platinum molecules

In a hollow-cathode discharge, molecules such as diatomic platinum hydride and platinum oxide have been obtained. The cathode was made of aluminium lined with a platinum foil which was sputtered by a discharge in argon gas. By studying the emission spectrum from the hollow cathode, it was found that, with oxygen in the argon, PtO was easily formed and that the experiments with PtO were easily reproducible. However, the formation of PtH and the isotopic molecule PtD was more sensitive to the experimental conditions. A new band spectrum was also observed, probably originating from the hitherto unknown molecule PtAl.

Enhanced coherent Raman emission from uniform plasmas

A mechanism for the coherent emission of radio and microwaves from a warm uniform plasma is proposed. The output power from this mechanism appears to have the characteristics of a classical parametric amplification process. An earlier kinetic theory model for radiation by the scattering of plasma waves in a homogeneous plasma is revamped and modified to incorporate the dominant role of longitudinal Rayleigh scattered waves which stimulate the emission of transverse combination radiation (sum and difference of impressed and natural frequencies) by the resonant Raman scattering process in the plasma. This results in intense radio or microwave radiation at approximately twice the plasma frequency, the intensity depending upon plasma parameters. This intensity, its angular pattern, and the threshold condition for its enhanced emission are calculated. Comparisons of the computed results with the laboratory observation of the radiation output from dc discharges in argon gas, and from a helium theta-pinch plasma are made. Both qualitative and quantitative agreement are found.

On some properties of ultrahigh-frequency gas discharge in argon: E V Belousov et al,Zh Tekh Fiz, 44 (1), 1974, 91–97 ( in Russian)

On some properties of ultrahigh-frequency gas discharge in argon: E V Belousov et al,Zh Tekh Fiz, 44 (1), 1974, 91–97 ( in Russian)

イオン衝撃加熱による蒸着装置の試作

The argon plasma, which contained highly concentrated argon ions, was produced by argon gas discharge of electrode-less of radio frequency. point end of rod type Ti target in argon plasma was bombarded with the argon ions by application of strong electrical field. Therefore, the temperature of the top of target was gradually raised.In the final state, the top of the Ti target was found to be melted and evaporated.An evaporation device was produced experimentally with the above-mentioned heating method. This device was tentatively used in order to make Ti thin films, which experiment turned out a success.The evaporated Ti particles were found to be ionized in passing through radio frequency electro-magnetic field. Then, the ionized Ti particles were easily centralized into ion beam state by making use of DC magnetic field.This device makes it possible to control the followings easily in wide range; an ionization rate of argon, an evaporation rate of Ti, and a degree of centralization of evaporated Ti particles respectively, because the mechanisms of the above-mentioned each systems in this device are those independent of one another.

Apparent Frequency Dependence of the Microwave Power Radiated from Gas Discharge Noise Sources (Correspondence)

Historically it has been assumed that the microwave power per unit bandwidth radiated from the plasma of typical argon and neon gas discharge noise sources is frequency independent. There are now both a priori basis and experimental evidence for questioning this assumption. For such frequency independence to exist over a frequency range of 100 MHz to 100 GHz the following conditions must be met: (1) /spl planck/ /spl omega/ / kT<<1; (2) proper matching of the discharge to the guide; (3) an appropriate level of absorptivity of the plasma for these frequencies; (4) a Maxwellian electron velocity distribution function; and (5) absence of collective oscillations. The first three conditions are shown to be met. The fourth condition involves the concept of a radiation temperature. Because the appropriate electron velocity distributions are not Maxwellian this radiation temperature does depend somewhat on frequency. This dependence is limited to a small region around the electron-atom collision frequency. For the discharges of concern it is shown that these collision frequencies are 10/sup 9/ to 10/sup 10/s/sup -1/ and therefore contained in the frequency range of interest. The fifth condition relates to the fourth and recently has been shown in theory to be untrue. Finally there is now available experimental evidence which appears to show a small (0.2-0.3 dB) variation of excess noise ratio with frequency on existing tubes. Suggestions for future experiments and interim considerations are made.

Avalanche-diode microwave noise generation experiments

This paper describes some experimental studies of the noise properties of avalanche diodes at X-band frequencies. The results obtained indicate that the diode has a potential application as a broad band microwave noise source with a noise temperature from 15 dB to 25 dB greater than an argon gas discharge tube, depending on the bandwidth of the diode circuit. These results were obtained independently but corroborate the recently reported results of Val'd-Perlov, Krasilov, and Tager.

Spectroscopic Determination of Temperature in Heavy Current Arc Discharge

The spectroscopic method of measuring relative intensities of two spectral lines has been used for determining the temperature of a plasma jet of argon gas and ac arc discharge of heavy current in air. Temperature distribution of the plasma jet was determined by using Abel's integral equation. The arc temperature of the weighted mean of the whole volume of ac arc discharge attained 35 by 103°K at 50 kA. By employing the measured electric field and temperature, a radius of arc column is calculated to be 2 cm at the same current.

Generation of Second Harmonic Radiation by a Microwave Maintained Plasma at Cyclotron Resonance†

ABSTRACT An experiment is described in which a gas discharge in argon is initiated and maintained within a waveguide by an incident X-band microwave signal. Cyclotron resonance is established between the microwave signal and a superimposed axial magnetic field. Second harmonic power is observed to be radiated from the discharge at K-band for a limited range of gas pressure. Theoretical calculations of the expected harmonic output are included and compared with experimental results.

Der Einflu� metastabiler Atome auf den statischen Durchschlag in Argon

A gas discharge in argon is initiated by an ultraviolet light pulse which releases 105 electrons at the cathode within 20 nsec. The time of built-up for the static breakdown is found to be in the order of msec. The oscillogram of the current near breakdown shows a fast component consisting of several successive avalanches caused by secondary electrons liberated by ions at the cathode and a slow component which is due to the electrons liberated by metastable atoms at the cathode. The second Townsend coefficient for argon ions and a nickel cathode is determined to beγ+= 2.5·10−3. The amount of electrons liberated by metastables at static breakdown is 25% of the total number of secondary electrons. The mean life-time of the metastables at 1,1 Torr and an electrode separation of 10 mm is found to be 2.2 msec, which is mainly due to de-exciting collisions at the electrodes.

The electric field distribution during the transition from Townsend to glow discharge in low pressure argon gas

The electric field distribution has been obtained at regular intervals during the transition from a Townsend to a glow discharge. A theoretical interpretation of the distribution has been satisfactorily obtained by using the Varney space charge equation. Measurements of the cathode field gradient have yielded values for the positive ion drift velocity over a wide range of E/p. These values compare favourably with the values for the Ar+ ion.

直線型放電におけるプラズマの挙動

Dynamical behaviors of plasma in linear pulse discharges of nitrogen and argon gases are observed electrically and optically. At the time of the first pinch of plasma cylinder, wave forms of total current of plasma show various shapes and values of differentiation of the current with time change from negative value to positive, with increase of longitudinal magnetic field (Bz=01, 150 gauss). Diameters of plasma at the time of the first pinch are measured from the photographic records taken by high speed streak camera. The diameters of plasma increase and mean constricting speeds of plasma cylinder decrease, with increase of Bz field. It is thought that strong radiation flashing to the perpendicular direction for time axis of the monochromatic streak photograph and all over the interior of the discharge tube at the time of the pinch, is originated from the excited radiation of neutral argon gas (ArI) left behind the constricting main plasma, in the case of argon gas discharge.