Development of Electronic Tubes

The main types of modern electronic tubes are briefly surveyed in this paper, together with their general uses. Tubes are classified according to electronic mechanism, and their origin is traced to three independent sources and several independent lines of development. The earliest group of electron-beam tubes made its appearance as the most direct result of intense scientific study of gas-discharge tubes prompted by William Crookes. These are: the Lenard tube (1894), the X-ray tube (Roentgen, 1895), and the cathode-ray tube (Braun, 1897). Another direct descendent of the Crookes tube is the mercury-arc rectifier (Cooper Hewitt, 1902) with all its modem derivatives, thyratron, phanotron, ignitron, and excitron. These are industrial tubes par excellence and have become quite indispensable in many branches of industry. Their importance grows rapidly. High-vacuum tubes, rectifiers, and pliotrons, through de Forest's audion (1908) and Fleming's valve (1904) are connected with the Edison effect observed in incandescent lamps (1884). This vast family includes kenotrons, and all radio and industrial high-frequency tubes. Ultra-high-frequency tubes stand apart in this class, since in their designing electron transit time and associated ultra-high-frequency circuits are two important factors to be considered. Special triodes (or tetrodes), magnetrons and velocity-modulation tubes are the main ultra-high-frequency types. Finally, independent of all previous groups stands the phototube, unspectacular, but one of the most important tools in modern industry. Its development is rooted in the photoelectric phenomenon observed by Hertz and scientifically studied by Hollwachs (1888), by Elster and Geitel (1912), and others.