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In the present work, breakdown characteristics in air and in Argon gas are studied in a discharge tube. The experiment is performed in a glass tube with two circular electrodes. A dc voltage (~ 300 – 600 V) is applied between the electrodes to create the discharge. The breakdown voltage is measured for different gas pressures at a fixed electrode gap. The Paschen curve is then obtained at different electrode gaps for two cases 1) with air as background gas and 2) with Argon as background gas. The working pressure is maintained in the range ~ 10-2 to 10-1 mbar and the electrode gap is varied in the range ~ 4 to 10 cm. The experimental results are compared with the theoretical Paschen curve and it is found that at smaller electrode gaps the minimum breakdown voltage is very close to the theoretical result. However, at larger electrode gaps the experimental breakdown voltages are relatively higher than the theoretical values. This deviation can be attributed mainly to factors such as non-uniform electric fields, surface roughness or contamination on the electrodes, formation of anode spots and secondary electron emissions [1, 2].
References:
[1] P. Mathew, J. George, Sajith Mathews T., and P. J. Kurian, “Experimental verification of modified Paschen’s law in dc glow discharge argon plasma,” AIP Advances, vol. 9, p. 025318, 2019.
[2] C Torres, P G Reyes, F Castillo and H Martínez “Paschen law for argon glow discharge,” in Journal of Physics: Conference Series, vol. 370, p. 012067, 2012.
