A grid-controlled secondary-emission electron multiplier am-plifier tube has been designed and built which can deliver an output pulse of five amperes into a load impedance of 100 ohms, with a rise time of less than 10 millimicroseconds and a transit time of less than 20 mil¬limicroseconds. The measured transconductance of the tube is 600,000 μmhos, and it can provide a positive output pulse with a positive grid input.nThe tube is constructed as a series of concentric cylinders, with the grid and cathode structure of a 6AG7 pentode serving as a con¬trolled emitter source. Outside the last grid, a series of four louvered, concentric dynodes are placed, with the first dynode serving as the missing pentode plate. Outside the last dynode are a screen-mesh col¬lector and a fifth dynode. From the fifth dynode, a solid cylinder, the output pulse is taken. The concentric geometry has several advantages. Space-charge difficulties are decreased because the current gain at each dynode may be kept at a high level without increasing the current density in proportion. Furthermore, the geometry is suited to a coax¬ial input and output for obtaining optimum rise-time characteristics.
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