Image Intensifiers for Nuclear Track Imaging

The electron image converter is now a proven device for amplifying a light image containing only a few photons per resolved picture element. Two-and three-stage electrostatically-focused cascaded image converters were made specifically for the purpose of intensifying the tracks of nuclear particles passing through a scintillation chamber. Gains as high as 50 per stage were obtained with an input equivalent to screen background as low as 105 photons per square cm per second (slightly more than 104 photoelectrons per square cm per second). At reduced voltage and gain, backgrounds were equivalent to about 100 electrons per square cm per second (the level of the thermionic emission). Scintillations of individual electrons were recognized. With a fast (P15) phosphor for the first screen, the microsecond Image storage accompanied by microsecond pulsing of the applied voltage across the second stage made possible complete elimination of tube background in photographs of nuclear tracks.