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Indian Journal of Pure & Applied Physics (IJPAP) >
IJPAP Vol.43 [2005] >
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 Code: | G01R33/14 |
| 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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