073 -- Paschen's Law Plasma Demonstration Chamber

I am building a plasma chamber apparatus to demonstrate Paschen’s Law by showing plasma arcs between electrodes in a vacuum chamber. A minimum breakdown voltage is needed to spark a plasma between two electrodes in a gas. Paschen’s Law relates this breakdown voltage to the pressure p of the gas and the length d of the gap between the electrodes. There exists an optimal product p✕d which minimizes the breakdown voltage, which is roughly (7.5 cm)✕(10–4 atm) in air. Three pairs of electrodes with different gap lengths will be shaped like a ladder. They will be connected in parallel so that the same voltage is applied across all of them. The gap lengths were chosen to contrast the optimal conditions, with two of the gaps corresponding to larger breakdown voltages. The vacuum chamber consists of a bell jar and raised base-plate to contain the electrodes. This chamber is connected to a vacuum pump, pressure gauge and regulator, and electrical contacts to the ground and high voltage. This plasma chamber will be usable for educational purposes and is portable.