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The streamer and return stroke concepts in positive corona breakdown are reviewed, and examined critically for the case of short (

The electronic system of this coincidence counter consists of two 13-stage Venetian blind photomultipliers coupled to a simple DeBenedetti-Richings coincidence circuit, followed by a medium-gain amplifier, pulse selector and scaler. The main feature of the system is its simplicity, chiefly realized by utilizing the quasi-linear transfer properties of the take-the-lesser type coincidence circuit. “Balance-point operation” permits the use of multiplier high voltage supplies and pulse amplifiers not possessing the high stability usually required for scintillation counting. The counter has been operated at 26°C with a tritium counting efficiency of 16% at a background of 100 c/min. The minimum detectable tritium concentration in water is 1.7 × 10−8 curie/liter. However, the time needed for the counter to “quiet down” after a change of sample is prohibitively long, 2–3 days. Of the background, nearly 50% seems to be caused by light interaction between the photomultipliers. Some suggestions for future improvements are given.

A complete, simple electronic adaptor unit is described which allows the use of an X-Y recorder with the Tektronix type N sampling oscilloscope system. The unit contains a pulse height averager circuit that is essentially a cathode follower pulse stretcher, and that gives a vertical (Y) channel mean output voltage proportional to the mean height of the short output pulses from the sampling oscilloscope, irrespective of their repetition rate. The unit has proved to be of value when recording electrical pulses of shapes fluctuating about a mean, as photomultiplier pulses due to very weak but identical photon pulses.