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INDUSTRIAL STRENGTH by MICHAEL RIORDAN

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INDUSTRIAL STRENGTH by MICHAEL RIORDAN THE INDUSTRIAL STRENGTH by MICHAEL RIORDAN ORE THAN A DECADE before J. J. Thomson discovered the elec- tron, Thomas Edison stumbled across a curious effect, patented Mit, and quickly forgot about it. Testing various carbon filaments for electric light bulbs in 1883, he noticed a tiny current trickling in a single di- rection across a partially evacuated tube into which he had inserted a metal plate. Two decades later, British entrepreneur John Ambrose Fleming applied this effect to invent the “oscillation valve,” or vacuum diode—a two-termi- nal device that converts alternating current into direct. In the early 1900s such rectifiers served as critical elements in radio receivers, converting radio waves into the direct current signals needed to drive earphones. In 1906 the American inventor Lee de Forest happened to insert another elec- trode into one of these valves. To his delight, he discovered he could influ- ence the current flowing through this contraption by changing the voltage on this third electrode. The first vacuum-tube amplifier, it served initially as an improved rectifier. De Forest promptly dubbed his triode the audion and ap- plied for a patent. Much of the rest of his life would be spent in forming a se- ries of shaky companies to exploit this invention—and in an endless series of legal disputes over the rights to its use. These pioneers of electronics understood only vaguely—if at all—that individual subatomic particles were streaming through their devices. For them, electricity was still the fluid (or fluids) that the classical electrodynamicists of the nineteenth century thought to be related to stresses and disturbances in the luminiferous æther. Edison, Fleming and de Forest might have been dim- ly aware of Thomson’s discovery, especially after he won the 1906 Nobel Copyright © 1996 by Michael Riordan. Adapted in part from Crystal Fire: The Birth of the Information Age, by Michel Riordan and Lillian Hoddeson, to be published in 1997 by W. W. Norton & Co. 30 SPRING 1997 PARTICLE Prize in physics. But this knowledge technology development slowly be- had yet to percolate out of academ- came an organized practice per- ic research labs such as the Caven- formed by multidisciplinary teams dish and into industrial workshops. of salaried scientists and engineers Although he had earned a Ph.D. in working in well-equipped industrial physics from Yale, in his daily prac- labs. As the century waxed and quan- tice de Forest remained pretty much tum mechanics emerged to explain a systematic tinkerer in the Edison- the mysterious behavior of electrons, ian vein, trying endless variations on atoms and molecules, these re- his gadgets in his halting attempts to searchers increasingly sported ad- improve their performance. vanced degrees in physics or chem- istry. A deeper understanding of the OLUMES COULD be writ- scientific principles governing the ten about the practical appli- behavior of matter gradually became Vcations that owe their exis- indispensable to the practice of in- tence to the understanding of dustrial research. As the noted his- electricity as a stream of subatomic torian of technology Thomas Hugh- particles rather than a continuous flu- es put it, “Independent inventors had id. While the telephone clearly an- manipulated machines and dynamos; tedated the discovery of the electron, industrial scientists would manip- for example, its modern manifesta- ulate electrons and molecules.” tions—cellular and touchtone phones, Few examples illustrate this evo- telefax machines, satellite communi- lutionary transformation better than cations—would be utterly impossible the case of the vacuum-tube ampli- without such knowledge. And the fier. For almost a decade after de For- ubiquitous television set is of course est invented it, his audion found lit- just a highly refined version of the tle use beyond low-voltage appli- cathode-ray tube that Thomson used cations in wireless receivers—as a to determine the charge-to-mass ra- detector of weak radio signals. He tio of his beloved corpuscle. The field simply did not understand that the of electronics, a major subfield of gas remaining in his tube was im- electrical engineering today, grew up peding the flow of electrons from fil- in the twentieth century around this ament to plate. At the higher volt- new conception of electricity, even- ages required for serious amplifica- tually taking its name in the 1920s tion, say in telephone communica- from the particle at its core. (We are tions, the device began, as one ob- perhaps fortunate that Thomson did server noted, “to fill with blue haze, not prevail in his choice of nomen- seem to choke, and then transmit no clature!) further speech until the incoming In parallel with the upsurge of current had been greatly reduced.” electronics, and in some part due to One corporation extremely inter- it, came a sweeping transformation ested in amplifying telephone signals of industrial research in America. was the American Telephone and Once the main province of highly Telegraph Company, then seeking to individualistic inventors search- develop a suitable “repeater” for ing for a fruitful breakthrough, transcontinental phone service. BEAM LINE 31 Among its leading scien- elements in excellent telephone re- tists was Frank Jewett, peaters. At the grand opening of the then working in the engi- Panama-Pacific Expositon held in neering department of its San Francisco on January 15, 1915, Western Electric Division. Alexander Graham Bell inaugurated In 1902 he had earned a the nation’s first coast-to-coast Ph.D. in physics from the telephone service, talking to his for- University of Chicago, do- mer assistant Thomas Watson in ing his research under Al- New York. Recalling this event in his bert Michelson and be- autobiography, Millikan observed friending Robert Millikan. that “the electron—up to that time Harboring a hunch that the largely the plaything of the scien- electrical discharges in tist—had clearly entered the field evacuated tubes might as a patent agent in the supplying serve as the basis for a suit- of man’s commercial and industrial able repeater, Jewett ap- needs.” proached his old chum, Thus convinced of the value of sci- who in 1911 sent one of his entific research in an industrial set- brightest graduate stu- ting, Western Electric incorporated J. J. Thomson inspecting electron tubes dents, Harold Arnold, to Western its engineering department as a sep- in 1923 with Frank Jewett, the first Electric. Here was a young man arate entity—the Bell Telephone Lab- president of Bell Labs. (Courtesy AT&T steeped in the new thinking, who had oratories—in 1925, naming Jewett its Archives and AIP Niels Bohr Library) just spent several years measuring first president. The very next year, the charges of individual electrons as an outgrowth of their research on on oil droplets. the performance of vacuum tubes When de Forest demonstrated his (also called electron tubes), Clinton audion to Western Electric scientists Davisson and Lester Germer estab- and engineers in October 1912, lished the wave nature of electrons, Arnold was present. He diagnosed which had been predicted a few years the blue haze as due to the recom- earlier by Louis de Broglie. For his bination of gas molecules that had pivotal work on electron diffraction, been ionized by energetic electrons. Davisson was to share the 1937 Then he solved its problems by use Nobel Prize in physics with the of high vacuum, an oxide-coated fil- British scientist George Thomson, ament, and other modifications dic- son of J. J. tated by a superior understanding Quantum mechanics soon ex- of the electronic discharge. (A similar plained the behavior not only of elec- development occurred simultaneu- trons in atoms but of the large osly at General Electric, but it lost ensembles of them that swarm about the ensuing patent fight to AT&T, freely within metals. Based on the which had wisely purchased the theoretical work of Enrico Fermi and appropriate rights to de Forest’s Paul Dirac, Bell Labs physicists even- patents.) tually figured out why an oxide- Within a year Western Electric coating worked so well on tungsten was making “high-vacuum thermi- filaments of vacuum tubes. It helped onic tubes” that served as active to lower the work function of the 32 SPRING 1997 Right: Clinton Davisson and Lester Germer with the apparatus they used to establish the wave nature of electrons. (Courtesy AT&T Archives) Bottom: Graph from their 1927 Nature article showing diffraction peaks observed in electron scattering from a nickel crystal. metal, thereby making it easier for electrons to escape from the sur- face—and substantially reducing the amount of power needed to heat a fil- ament. Such a fundamental under- standing of the physics of electrons proved crucial to further engineering advances in vacuum tubes that saved AT&T millions of dollars annually. N THE LATE 1920S and early 1930s, Felix Bloch, Rudolph IPeierls, Alan Wilson and other European physicists laid the foun- dations of modern solid-state physics in their theoretical studies of how above a few hundred megahertz, useful properties by finding physical waves of electrons slosh about with- where electron tubes had proved use- and chemical methods of controlling in the periodic potentials encoun- less. Crystal rectifiers, with a deli- the arrangement of the atoms and tered inside crystalline materials. cate metal point pressed into a ger- electrons which compose solids.” Their work resulted in a theory of manium or silicon surface, filled the The most important postwar solids in which there are specific al- gap nicely. By the end of the War, breakthrough to occur at Bell Labs lowed (or forbidden) energy levels— methods of purifying and doping was the invention of the transistor called “bands”—that electrons can these substances to make easily con- in late 1947 and early 1948 by John (or cannot) occupy, analogous to the trolled, well-understood semicon- Bardeen, Walter Brattain, and Wil- Bohr orbitals of early quantum the- ductors had been perfected by sci- liam Shockley.
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