Conduction and Breakdown in Gases

Vacuum Breakdown

Vacuum Breakdown: In the Townsend type of discharge in a gas described earlier, electrons get multiplied due to various ionization processes and an electron avalanche is formed. In a high Vacuum Breakdown, even if the electrodes are separated by, say, a few centimetres, an electron crosses the gap without encountering any collisions. Therefore, the current …

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Breakdown in Non Uniform Fields

Breakdown in Non Uniform Fields: In Breakdown in Non Uniform Fields, such as coaxial cylinders, point-plane and sphere-plane gaps, the applied field varies across the gap. Similarly, Townsend’s first ionization coefficient (α) also varies with the gap. Hence αd in Townsend’s criterion [refer to Eq. (2.22)] is rewritten by replacing αd by Townsend’s criterion for breakdown …

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Paschen Breakdown

Paschen Breakdown | Paschen’s Law | Paschen curve It has been shown earlier (refer Sec. 2.6) that the Paschen Breakdown criterion in gases is given as where the coefficients α and γ are functions of E/p, i.e Substituting for E have in the expressions for α and γ and rewriting Eq. (2.26) we have This equation shows a …

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Formative Time Lag

Formative Time Lag: Formative Time Lag – In the previous section, the mechanism of spark breakdown is considered as a function of ionization processes under uniform field conditions. But in practical engineering designs, the breakdown due to rapidly changing voltages or impulse voltages is of great importance. Actually, there is a time difference between the …

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Experimental Arrangement to Measure Ionization Coefficients

Experimental Arrangement to Measure Ionization Coefficients α and γ: The Experimental Arrangement to Measure Ionization Coefficients is shown in Fig. 2.2. The electrode system consists of two uniform field electrodes. The high voltage electrode is connected to a variable high voltage d.c. source (of 2 to 10 kV rating). The low voltage electrode consists of a …

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