Brilliant Development of Vacuum Tubes by Professor Emory L. Chaffee Will Reduce Industrial Costs by Many Thousands

A major scientific development, which will mean the saving of thousands of dollars worth of electric power annually through increased efficiency of the vacuum tube, or "electric valve," in controlling electricity, was announced last Wednesday by the Cruft Laboratory of Communication Engineering.

The findings, which are considered to be one of the greatest contributions to the development of the use of power vacuum tubes in recent years, are the result of ten years' work in the Harvard laboratories by Emory L. Chaffee, Gordon McKay Professor of Physics and Communication Engineering.

Chaffee has developed the first satisfactory methods of testing the complex operation of vacuum tubes and thus increasing their efficiency through scientific and mathematical analysis.

In replacing the relatively crude, haphazard, and extremely expensive method of improving vacuum tube performance by trial and error, hitherto universally applied, Chaffee is believed to have opened the way to much wider development and use of the electric "valves."

His work is regarded by authorities as a signal triumph of laboratory and mathematical skill over one of the most complex problems in electrical engineering posed before this generation.

While the vacuum tube is one of the most vital tools of modern industry and science, with hundreds of millions of units now in operation, the tube has been developed slowly in efficiency because of the forbidding jungle of interlocking mathematical functions involved in its operation.

The intricacy of the formulas involved is indicated by the fact that in any vacuum tube the electric potentials applied present four variable factors, all reacting to the slighest deviation of any one.

For the first time through the techniques developed by Chaffee, engineers are able to resolve these variables through mathematical calculations backed by routine laboratory tests,--thus arriving rationally at more efficient combinations of the variables.

In their first immediate application to industry, Chaffee's findings are expected to affect markedly the manufacture and use of the giant power tubes through which radio stations daily control and transmit hundreds of thousands of kilowatts of electrical energy.

The Harvard work shows that in many cases the tubes now in use in radio broadcasting may be so altered and activated that their power output may be doubled, and their efficiency greatly increased.

Besides the complexity of performance, a major hindrance to experimentation with the huge power tubes, which sometimes are as much as six feet high, has been their cost, about $5,000 a unit.

Chaffee has developed the first technique by which tests of the behavior of large power tubes can be made with small models.

This extension of so-called dimensional analysis, used for years in the design of turbines, ships, and airplanes, into the highly complicated region of the interaction of electrical potentials, is regarded as one of the most brilliant of Chaffee's accomplishments.

Use of the small scale model in only one of four methods of investigating power tube operation achieved by Professor Chaffee.

Using one of his methods, it is possible to calculate the performance of a tube from graph curves based on the characteristics of the unit.

For another method, Chaffee has developed apparatus by which the power tube operation can be tested at the ordinary, household, current frequency of 60 cycles, for which electrical measuring instruments are standard and extremely accurate.

Hitherto, meaningful tests of the tubes could be made only at the extremely high frequencies of thousands of cycles per second, under which they operate in broadcasting. At these high frequencies, electrical measuring equipment is often erratic and unreliable.

Finally, from his experiments, Chaffee has been able to formulate theories of power tube operation, from which actual performance can be predicted far more accurately than ever before.

Professor Chaffee's techniques are applicable not only to broadcasting tubes, but also throughout the electrical industry, wherever these electric "valves" are employed.

Capable of amplifying current, altering wave shapes and frequencies, detecting electric impulses, oscillating, rectifying current, and many other duties, these modern "magic lamps," first utilized thirty years ago, now have hundreds of uses in industry, research, and entertainment.

"Repeater" tubes are used to magnify the voice thousands of times in long-distance telephoning; sound movies, the "electric eye," remote control devices, X-ray, and television are all applications of the vacuum tube.

Throughout the scientific world, in physics, chemistry, medicine, and other fields, the tubes are used wherever delicate and complex control of electricity is required.

The underlying principle of the vacuum tube, first detected by Edison during his experiments with electric light a half century ago, is that when two wires, one positively charged, and the other negatively, are inserted into a vacuum, and the negative wire or filament is heated, a current passes from the filament through the void to the positive terminal.

His observation that current would pass in only this one direction through the tube was first put to work thirty years ago by J. A. Fleming, an English physicist, who saw a possible use for this feature in the detection and rectifying of radio signals, then being pioneered by Marconi.

The rough control over current, which electricians were able to exercise through changing the potentials on the positive and negative terminals of the original tubes, was rendered extremely sensitive and intricate with the addition, by Dr. Lee De Forest, of an independently charged grid of wire between the heated filament and the positively charged plate.