A look at the future of tubes

Solid-state devices are presenting severe competition to electron tubes in many applications where only a few years ago tubes reigned supreme. So spectacular have been the inroads of solid-state devices that some engineers have wondered if eventually all tubes would be replaced, or at least if tubes in the future would play only minor rolls. A comparison of the basic characteristics of tubes and solid-state devices does not bear this out. It appears certain that inroads will continue, mainly in applications involving low power and low frequency. However, where high power is needed, tubes may be expected to maintain dominance. Thus tubes should be important in cooking, food processing, and industrial heating, in providing high RF power for phased array radars, in magnetohydrodynamic power generation, in thermionic energy conversion, in drilling and machining, and in ion propulsion for space travel. Certain tubes, such as the traveling-wave tube, are attractive because of inherently wide bandwidth. They should continue to compete wherever wide bandwidth is needed, such as in microwave power amplification for satellites. There is presently no strong reason to feel that tubes will not continue to be employed in radiation sensing and in display. Finally, tubes of special design have been useful and will continue to be useful in basic research as devices in which to stage experiments. Examples of this are particle accelerator, tubes for plasma diagnostics and a recently announced electron cyclotron maser.