Spark Investigation by the Wilson Chamber

Abstract

SEVERAL years ago, one of the present writers (U. N.) engaged in a study concerning the form of long electric sparks at the laboratory of the Institute of Physical and Chemical Research in Tokyo under Prof. Terada. We succeeded then, by using a quartz-fluorite lens, in taking a photograph of the brush discharge immediately preceding the main spark¹. This preceding discharge is rich in ultra-violet light, and more complicated and extended in its form than the succeeding main spark, giving an aspect as appendages to the luminous spark track. This result led us to look for the other form of discharge which cannot be photographed even with the quartz-fluorite lens. The use of Prof. Wilson's cloud chamber is at our present stage of knowledge the only method suitable for observing a process of discharge that is not accompanied by any luminous phenomenon. We then tried, on the suggestion of Prof. T. Terada, to take a Wilson photograph of the ions produced by a spark, but did not succeed in obtaining a satisfactory one. Later on, in the course of conversation with Prof. C. T. R. Wilson at Cambridge, I was given a great deal of advice on this problem and decided to take up this subject again.