Miniature Photomultiplier for Scintillation and Space Use

A rugged miniature photomultiplier has been developed which is only 8 mm in diameter. The electron multiplying element is a single channel multiplier. Photoelectrons from the 5 mm diameter cathode are electrostatically focused into the channel multiplier without need for a funnel or cathode-to-channel bias. This photomultiplier is a two-terminal device and uses no external resistors. The high gain characteristics (~108 at 3,000V), and the single-electron pulse height distribution (FWHM ¿0.6), make the tube ideal for pulse-counting applications. The small diameter of this tube suggests applications in close-packed arrays and mosaics for scintillation imaging. This tube can be used as a scintillation spectum analyzer with good resolution even at high gains where there are greater than 109 anode electrons per scintillation event. The structure can also be employed in a windowless configuration as a particle or x-ray detector. In this modification apertures as large as 5 × 7 mm2 are possible. One use is as the detector in an Auger apparatus, where the high-gain output pulses allow precision digital data handling techniques and long drift-free integration time.