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IJPAP Vol.43(12) [December 2005] >


Title: Potential-variation of a time effect on the average of counts in argon at a low pressure subjected to low frequency silent electric discharges
Authors: Salvi, S V
Pimpale, Sushama S
Keywords: Silent discharge
Ageing
Mobility
Average light-effect
Penning-effect
Budde-effect
Issue Date: Dec-2005
Publisher: CSIR
IPC CodeG01R33/14
Abstract: A series of observations at a definite kV (rms) was taken for the time-variation of discharge counts in which the arithmetic mean of counts in dark (ƩCD)/n; in light (ƩCL)/n and their associated net effect (ƩDC)/n [= (ƩCL)/n - (ƩCD)/n] of irradiation were calculated; after that the discharge tube (1) was short aged for 5 min at 2.45 kV (rms) and the discharge was then discontinued; re-applying the same potential kV (rms) to the same tube, the variation with time of exposure to discharge of counts was again recorded and (ƩΔC)/n re-determined as previously. It has now been observed that almost always (ƩΔC)/n shows a greater value in the earlier that in the latter series. Thus, several series of experiments were carried out at different values for the applied potential in each of which (ƩΔC)/n was measured as a function of the applied potential increased progressively, at a constant window width of 0.07 kV(rms), to a maximum. Similarly, the results in a series of comparative measurements for two discharge tubes have been reported. It was observed that the increase of (ƩΔC)/n as a result of ageing, i.e. due to previous exposure to the discharge, was very appreciably larger in the case of a discharge tube (1) which had been rendered comparatively insensitive in regard to the average effect of irradiation, than a fresh one which showed the familiar behaviour of an irradiation. The average light effect (ƩΔC)/n decreased with ageing and disappeared finally. It revived to its original value after allowing a period of rest of 24 hr. Threshold voltage, Vg, in aged tube was appreciably smaller than that in the freshly prepared one. This is ascribed to a lowering of the electrode surface work function due to ionic bombardment under discharge. + (ƩΔC)/n inverted to –(ƩΔC)/n with ageing and then decreased. The increase in + (ƩΔC)/n with ageing is attributed to an enhanced photo-electron emission caused by the decrease in the work function. The decrease in –(ƩΔC)/n is ascribable to the deconditioning of the adsorption like boundary layer formed during discharge. The results show that –(ƩΔC)/n is associated with a decrease in ionic mobility. This lends support to the Joshi¢s theory for the mechanism of –(ƩΔC)/n, n being the total number of readings taken between counts and exposure –time at each voltage.
Page(s): 931-938
ISSN: 0975-1041 (Online); 0019-5596 (Print)
Source:IJPAP Vol.43(12) [December 2005]

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