Abstract
In the paper "Some Researches on Impulse Voltage" (this Journal, April, 1922) Bekku and Tanno have shown that the sphere gap sometimes discharges and sometimes fails to discharge even with the same condition of impulse circuits. The authors called phis phenomena "the ambiguity of the spark discharge." These experiments were conducted with the sphere gaps of diameters 1.0cm., 3.8cm and 6.25cm. and also with the needle gap. The gap length was 1 to 3mm. The conclusions arrived at were that the ambiguity is most remarkable for 3.8cm. sphere gaps and less for those with 1.0cm, nor 6.25cm, diameters. Also the ambiguity can't be recognized for needle gaps. The creaning of the surface of the sphere electrodes decreases the ambiguity.
The present author suggests that the phenomena may be explained by the casual ions in the air. Assuming the number of the casual ions to be 1500 per cubic cm the mean distance between ions is 0.8mm which is in the same order of the gap length used in the experiments and the intensity of the field at which the casual ion exists varies in considerable degree owing to its position and it is more so if the surface of electrodes is not clean. Thus one cause of the ambiguity is the position of the casual ions.
Another cause is the sweeping effect of the casual ions by the electrode potential. If the casual ion is attracted to the electrode before it has obtained the kinetic energy enough to ionize the neutral molecules, there will not occur any discharge. This sweeping effect is much dependent on the position and the polarity of the casual ion relative to the electrodes.
The non-existence of the ambiguity in the needle gap may be explained by fore-running corona formation in that type.
It is also suggested that the ambiguity will be less and finally vanish as the gap legnth or the density of the casual ions increase.
