Continuous spectrum x-rays from thin targets

Abstract

Technique is described for the use of thin metal foils as anticathodes in X-ray-tubes. The continuous radiation from these foils is analyzed by a crystal, the intensities being measured by a photographic comparison method. It is indicated that the high-frequency limit of the continuous spectrum from an infinitely thin target consists of a finite discontinuity. (The corresponding thick target spectrum has only a discontinuity of slope.) The energy distributions on a frequency scale are approximately horizontal, for gold and for aluminum, and for ^=40°, 90°, and 140°, where \I/ is the angle between measured X rays and cathode stream; this agrees with Kramer's, but not with Wentzel's, theory. The intensities for these values of \p are roughly 3:2:1, respectively; theories have not yet been constructed for the variation with \p of resolved energy, but it is pointed out that the observations do not support a supposed quantum process in which a single cathode ray, losing energy hv by interaction with a nucleus, radiates a single frequency v in the continuous spectrum. The observations do not support the "absorption" process assumed by Lenard, in which cathode rays, in penetrating a metal, suffered large losses of speed not accompanied by radiation. The manner in which thick target spectra are synthesized from thin is discussed, and empirical laws are formulated describing the dependence on \f/ of thick target continuous spectrum energy. A structure for the moving electron is proposed which explains classically X ray continuous spectrum phenomena, and seems to have application in other fields as well.