Dj A Bosan

Dependence of time of breakdown on electrode temperatures in nitrogen filled diodes

Time delays of electrical breakdown in a gas-filled diode (td) were measured as a function of the time between two successive measurements ( tau ) at cathode temperatures of 300K, 523K and 673K. The diode was filled with nitrogen at 4 mbar with an oxygen impurity of about 10 ppm. It is shown that the breakdown time delays at 673K are one order of magnitude smaller than those at 300K.

The study of the non-radiative life-time of the 1S5 metastable states of neon atoms under its own gas pressure of 13.3 mbar

The probability of electrical breakdown in neon is investigated under a pressure of 13.3 mbar, using the breakdown time-delay measurement method. It is found, by applying a laser spectroscopy technique, that the 1S5 metastable states of neon atoms dominantly contribute to the breakdown probability in the moment when more than 1 s has passed after the previous discharge. With this method the presence of 1S5 states of Ne atoms is detected in the gas, under the pressure mentioned, up to about 500 s after the cessation of the breakdown.

Distribution of time delay of electrical breakdown in nitrogen

Gives the distribution of experimentally obtained values of time delay of electrical breakdown (td). Measurements of td were made on a specially made nitrogen-filled diode at 13.33 mbar pressure. The results show that the distribution form is easily identifiable after about 500 successively measured td values, and that its form may be estimated after about 100 successively measured td values. These distributions were fitted using the least-squares polynomial approximation method. It was found that the best approximation is obtained by the seventh-order polynomial. Laues distributions for three groups of successively measured td values, in the range of one millisecond to several seconds, have the same form as those previously obtained by Meek and Craggs (1978), where td values were of the order of one microsecond.

The self-quenching process and half de-excitation time of metastables in a nitrogen afterglow

The dependencies of electrical-breakdown time delays td on the afterglow period tau were measured and the dependence of the mean values td on tau , using the so-called memory curves td=f( tau ), was established in nitrogen-filled diodes at 1.3 mbar and 13.3 mbar. The corresponding time-dependent variations of metastable concentration n, i.e. the curves n=F( tau ), were derived, where, at afterglow periods exceeding 1 s, the metastable molecules were predominantly in the N2(A3 Sigma u+) state. A physical model of metastable de-excitation processes has been proposed and, by solving its differential equations, the following dependencies and constants were obtained: (1) the theoretical dependence of metastable concentration on the afterglow time-the curve n=F( tau ), (2) the range of n0, the initial concentrations, which are also saturation concentrations of metastables reached in discharges, (3) the metastable concentration-independent constant k in the equation td=k/n, (4) the dependence of the half de-excitation time T1/2 on the afterglow period, T1/2= phi ( tau ), and (5) the dependence of Z on the afterglow period, Z= Phi ( tau ), where Z is the concentration dependent ratio between the de-excitation rate via binary metastable-metastable collisions and the total rate via all other considered de-excitation mechanisms.

Influence of electrode surface and some gas phase processes on electrical breakdown in nitrogen-filled diodes

The role of the electrode surface and some gas phase processes in the production of electrons which initiate electrical breakdown is investigated. The results show that to achieve approximately constant secondary electron emission in these experimental conditions it is necessary to perform about 1000 breakdowns. The experiments indicated that the initial electrons are created by the impact of N2 metastable states on the cathode and the nonradiative lifetime of these states depends on the gas pressure.

Laue distribution of large values of time delay of electrical breakdown in nitrogen

This paper gives the Laue distribution of time delay of electrical breakdown (td) for five pressure values of nitrogen in gas-filled diodes. Distributions were obtained for 20% overvoltage, and passive time ( tau ) 5 s and 7.2*103 s. The breakdown in nitrogen is induced by long-lived metastable states formed in the previous gas ionisation. The results show that the Laue distributions also hold for such groups of data when td varies between a fraction of a second and several hundreds of seconds.

The role of neutral metastable molecules in the breakdown probability and glow discharge in nitrogen

This is the summary of results of four experiments carried out in order to establish the initiators of electric breakdown in gases after long afterglow periods , particularly the role of molecules in the state in nitrogen. By illuminating nitrogen-filled measuring diodes by nitrogen-filled discharge lamps it was uniquely established that (i) a prolongation of the breakdown time delay, (ii) an increase in the breakdown voltage, (iii) a decrease in the stationary glow current and (iv) a shortening of the discharge quenching time occur due to optogalvanic de-population of the mentioned metastable state. Thus molecules and/or atoms in metastable states do considerably influence the breakdown probability as much as they contribute to the maintainance of glow-discharge currents.

Stabilisation of some characteristics of gas-filled diodes by electrical breakdowns

The conditions of the stabilisation of static breakdown voltage Us and time delay of electrical breakdown td with successive electrical breakdowns in gas-filled diodes with cold metallic electrodes have been studied. The diodes had the following electrode-gas combinations: Al-N2, Fe-H2, Cu-N2, CuH2, Fe-Ar, Fe-Kr and Fe-Xe. The number of breakdowns N necessary for stabilisation in the various diodes has been found. It was shown that besides irreversible, long-term changes during the stabilisation, there also exist reversible, short-term changes of Us with every break of the measurements of about 24 hours.

The influence of light from a nitrogen gas discharge lamp on the concentration of metastable species and on the time delay to electrical breakdown in nitrogen-filled diodes

The analysis of measurements of the overvoltage dependence of time delays to electrical breakdown in nitrogen-filled diodes under various illumination conditions confirms the role of long-lived metastable species. After long periods of afterglow the concentration of molecules significantly influences the breakdown probability as well as the magnitude of the glow-discharge current.

Current oscillations in gas-filled diodes in sub-normal glow discharge

The current oscillations in gas-filled diodes were investigated in sub-normal glow discharge. It was found that the frequency of these oscillations, in a given circuit, depended only on the negative value of dU/dI. Also it was found that, in the same circuit, the semiconductor components with equal values of dU/dI generated oscillations with equal frequencies.