Abstract
Breakdown voltage of a gas is the required voltage to start a discharge or electric arc through the gas. Paschen’s law describes the characteristics of gas breakdown voltage between two electrodes. This law states that the Gas breakdown voltage(VB) depends only on the product of gas pressure (p) and gap length(d) between electrodes (VB=f(pd)). In this paper, the effect of electrode separation length(d) and electrode radius (r) on gas breakdown voltage is studied experimentally. A gas discharge system with a large gap length compared to electrode radius is used for the study. Paschen curves are plotted for different electrode separation lengths and electrode radii. It is observed that gas breakdown voltages deviates from Paschen’s law and depend on the d/r ratio also in addition to the product of gap separation and pressure, i.e. VB=f(pd,d/r). This relation, already reported in the analyses of micro gap discharge and theoretical studies, is known as modified Paschen’s law. In order to experimentally verify the modified Paschen’s law in large discharge gaps, many experiments are conducted by varying both electrode separation and electrode radii but keeping the d/r ratio always same. It is observed that for different discharge system geometries, if d/r ratio is same, the break down voltages are same for same pd value. The Paschen’s curves are also plotted for different experiments and it is observed that the curves overlap if d/r ratio is set same for all experiments. Thus, the work presented in this paper experimentally verify the modified Paschen’s law.
Highlights
DC glow discharge plasma has wide range of applications in microelectronic industry, material surface cleaning, plasma polymerisations, optical emission spectrometry (GDOES) and mass spectrometry (GDMS).1,2 The DC glow discharge is often created by applying high voltage between two electrodes in a chamber containing low pressure gas
The breakdown voltage (VB) can be written as VB = f(pd). Both A and B are gas dependent constants defined for a particular E/p ratio, where E is the electric field and E/p signifies the electric stress per pressure
It can be deducted from Equation (10) that the breakdown voltage is a function of pd and d r
Summary
DC glow discharge plasma has wide range of applications in microelectronic industry, material surface cleaning, plasma polymerisations, optical emission spectrometry (GDOES) and mass spectrometry (GDMS). The DC glow discharge is often created by applying high voltage between two electrodes in a chamber containing low pressure gas. DC glow discharge plasma has wide range of applications in microelectronic industry, material surface cleaning, plasma polymerisations, optical emission spectrometry (GDOES) and mass spectrometry (GDMS).. The DC glow discharge is often created by applying high voltage between two electrodes in a chamber containing low pressure gas. When the voltage exceeds a particular value called breakdown voltage(VB), the electrical discharge occurs through the gas. In 1889, Louis Carl Heinrich Friedrich Paschen developed a law known as Paschen’s law, which states that the electrical breakdown voltage is a function of the product of operating pressure(p) and inter-electrode distance(d), that is, VB = f(pd). A detailed knowledge about the required minimum breakdown voltage to initiate gas discharge will help to improve the application levels of glow discharge A curve that is plotted by taking pd along the x-axis and VB along y-axis is called Paschen curve. A detailed knowledge about the required minimum breakdown voltage to initiate gas discharge will help to improve the application levels of glow discharge
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