This paper is based on a study to analyze and classify high-power RF tubes for possible application to space-borne linear accelerators at frequencies of 425, 850, and 1700 MHz. Devices considered included relatively conventional tubes such as klystrons, klystrodes, magnetrons, and crossed-field amplifiers; various novel devices such as the trirotron, timatron, lasertron, and gigatron; Soviet accelerator tubes (the martotron, gyrocon, and magnicon); the peniotron; and the resnatron. Primary factors considered in analyzing the devices were accelerator compatibility, weight, and efficiency. In addition, problems of thermal management, regulation, pulsing, and operating voltage were addressed. Several suggestions, recommendations, and results were generated during the study. A new magnetron configuration, called the nonresonant magnetron, which should be stable when operating into a highly reactive load, was proposed. The possibility of magnetically regulating and pulsing crossed-field devices in order to reduce system weight and increase system efficiency was briefly examined. The review of various tetrode-like devices (resnatron, trirotron, etc.) indicates that a radial version of the klystrode should be feasible. This device would have the low weight and high efficiency of present klystrodes but would operate at about 1/3 of the voltage. The review of tetrode-like devices also indicates that efficient operation of gridded tubes at 1700 MHz should be possible. Several traveling-wave-resonator tetrodes (the trirotron, martotron, and timatron) have been proposed but none have been built. All have predicted efficiencies over 80% and should be lightweight devices. An overall efficiency for a klystron of 74% was demonstrated nearly 20 years ago. With a multistage depressed collector, this efficiency should increase to at least 80 to 85%. Multistage depressed collectors for use on megawatt tubes have not been, but should be, investigated. The gyro-peniotron amplifier promises to provide an efficiency in the 80 to 85% range (with the use of a depressed collector) and appears to be a lightweight candidate for operation at 1700 MHz.
