A New High-Gain Multiplier Phototube for Scintillation Counting

This paper describes the RCA-6810, a head-on type of multiplier phototube having an S-11 response and intended for use in high-speed scintillation counting. This tube features a 2-inch-diameter, semitransparent cathode, and has a fourteen-stage, in-line, electrostatically-focused, silver-magnesium dynode structure. The mechanical construction of the tube and the method of assembly are described. With a supply voltage of 2000 volts, the 6810 is capable of multiplying feeble pulses 12.5 million times and has a luminous sensitivity of 750 amperes per lumen. With the maximum rated supply voltage of 2300 v, the amplification factor is 66 million and the luminous sensitivity 4000 a per lumen. Output current pulses of 0.7 a may be utilized. Data showing the linearity of the output over a wide range of light levels are given. Other properties of the tube such as speed of response, after-pulses, and time resolution capability are discussed, and the effect of a magnetic field on performance is described.