Validating the collision-dominated Child–Langmuir law for a dc discharge cathode sheath in an undergraduate laboratory

Abstract

In this paper, we propose a simple method of observing the collision-dominated Child–Langmuir lawin the course of an undergraduate laboratorywork devoted to studying the properties of gas discharges. To this end we employ the dc gas discharge whose properties are studied in sufficient detail. The undergraduate laboratory work itself is reduced to registering the voltage drop across the electrodes, the discharge current as well as the cathode sheath thickness. We can easily perform the measurements of all three quantities with sufficient accuracy in a laboratory equipped with vacuum pumps.