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Measurements are made of the fast striations immediately after ionization begins in an electrical discharge. First the basic phenomena leading to the existence of the so-called wave of stratification, produced by the external perturbation of an unstriated positive column, is given. It is explained that the analysis of the latter problem based on these phenomena leads to formulations that predict the presence of slow as well as fast striations. The result of this formulation for the fast striations is given. The formulation is modified to obtain results more suitable for the experimental technique used. For the measurement a microwave signal is impinged on the discharge tube that is ionized by a high-voltage pulse. The signal is reflected from the dense layers of ionized gas that are successively formed along the discharge tube and is shifted according to Doppler effect. The shifted signal is mixed with the incident microwave signal in a mixer and the difference frequency is observed on a spectrum analyzer. The klystron oscillator operates on continuous wave (cw) mode and the signal is frequency modulated by the velocity variations of the wave of stratification so that the system can be considered as a special superheterodyne microwave receiver. The results are of the same order of magnitude as those predicted by an analysis made for the case when an unstriated positive column is externally perturbed in order to artificially produce striations. On the basis of this result and other investigations made under prebreakdown and glow conditions, it can be concluded that (a) there may be inter-relationships among the parameters of striations occurring immediately after ionization is initiated, during the entire period of prebreakdown, and in the positive column, and (b) the phenomena leading to striations start with beginning of ionization and grow with its growth. As an outcome of such conclusions further work is recommended for the investigation of the origin and temporal evolution striations in all phases of an electrical discharge.

The formation of striations in a normal glow discharge has been correlated with a relaxation-type phenomenon occurring at the cathode dark space-negative-glow interface and caused by cathode instabilities. A beamlike stream of electrons, in excess of that number necessary to maintain the normal glow brought about by cathode instabilities, is postulated to cross the cathode-fall region and to interact with neutrals in the negative glow causing a surplus of positive ions at the interface between the cathode dark space and the negative glow. This group of positive ions constitutes a positive striation which in turn is accelerated toward the cathode. The experimentally observed times for these striations to cross the cathode-fall region give a velocity of approximately 104 cm/sec, which is in good agreement with other observations of positiveions striation velocities.