On the rôle of tube walls, and surface and space charges in electrical discharges through rarefied gases

Abstract

Several matters pertaining to the part played by tube walls, and surface and space charges in electrical discharges through rarefied gases, are briefly discussed, and experiments are described which throw light on some of the processes involved in such discharges. Measurements made under identical conditions of the falls of potential between striæ in the positive columns of discharges in hydrogen at various pressures in two glass tubes of different diameters showed that for pressures above 1.1 mm. these falls were increasingly greater in the larger tube. The results of experiments done with discharges produced under unusual conditions and bearing on the radial and axial fields present in the positive columns of discharges are described, and photographs of some of the discharges are reproduced in a part of which the positive column was made to pass through a long metal tube placed inside of the glass discharge tube, the two ends of the metal tube being at times both open and at other times both closed with wire gauzes of fine mesh. The potential assumed by the metal tube and the current flowing through its walls were measured, and special experiments were done to elucidate the process by which the current manages to penetrate the more or less field-free space inside the metal cylinder. The distributions of the space and surface charges along the length of a glass discharge tube were measured separately, at least roughly, and the nature of these distributions was found to depend markedly upon whether the anode or the cathode of the discharge tube was connected to earth, although the combined effects of the two charges of necessity produced the same field distribution within the discharge tube in both cases. The gases used in the experiments were air and hydrogen.