A New Type of High Power Vacuum Tube 



By W. WILSON 



Synopsis: The type of vacuum tube described in the present article is 

 likely to become one of the most remarkable devices of modern electrical 

 science. Vacuum tubes capable of handling small amounts of power have 

 been extensively used during the past few years as telephone repeaters 

 and as oscillators, modulators, detectors and amplifiers in radio trans- 

 mission and other fields. Practically all such tubes have depended upon 

 thermal radiation from the plates to dissipate the electrical energy which in 



the device necessarily absorbs during its operation. With present methods i^^ 



of construction, and using glass for the containing V^ulb, a fairly definite 

 upper limit can be set for the power which a radiation cooled tube can 

 handle; as the author points out, this limit gives a tube capable of delivering 

 about 1 to 2 k. w. when used as an oscillator. 



Contrasted with this, one of the water-cooled vacuum tubes described 

 herewith, although scarcely two feet in length and weighing only ten 

 pounds, is capable of delivering 100 k. w. of high frequency energy. Another 

 tube of similar construction, but somewhat smaller in size, and capable of 

 delivering about 10 k. w. is also described. It is expected that these water- 

 cooled tubes will find important applications in radio telephony and 

 telegraphy. 



Although the [irinciple of operation of the water-cooled tube described 

 in this article is identical from an electrical point of view with that of the 

 small tubes which are now so very familiar, their practicability has only it 



been made possible by a new and striking development in the art of seal- 

 in? metal to glass. In the case of the 100 k. w. tube the seal between the 

 c>lindrical copper anode and glass portion is 3.5 inches in diameter. 



The remarkable character of these copper-in-glass seals is evidenced 

 by the fact that they do not depend upon a substantial equality between 

 the coefficient of expansion of the metal and glass. To Mr. W. G. Hous- 

 keeper of the Bell System Research Laboratory at the Western Electric 

 Company, goes the credit for developing the copper-in-glass seals. As 

 the article brings out, Mr. Houskeeper has also invented means for sealing 

 heavy copper wire and strip through glass in such a way that the best 

 vacua can be maintained under wide changes of temperature. — pAlilor. 



THE development of wireless telephony and the use of continu- 

 ous wave transmission in wireless telegraphy have led to the 

 general adoption of the vacuum tube as the generator of high fre- 

 quency currents in low power installations. 



The ordinary form of vacuum tube is, however, ill suited for the 

 handling of large amounts of power, and at the large wireless stations 

 where the plant is rated in hundreds of kilowatts either the arc or 

 the high frequency alternator is used. 



The undoubted advantages to be derived from the use of vacuum 

 tubes, especially in the field of wireless telephony where the output 

 power must be modulated to conform to the intricate vibration pat- 

 tern of the voice, has led to a demand for tubes capable of handling 

 amounts of power comparable with those in use at the largest stations. 



That the development of such tubes was of great importance was 

 recognized by the engineers of the Bell Telephone System in the 

 early days of the vacuum tube art. The experiments at Arlington, 



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