Papers

AVS1997 Session EC-MoA: The Discovery of the Electron in 1897

Monday, October 20, 1997 1:40 PM in Main Ballroom (Hilton)

Monday Afternoon

Start	Invited?	Item
1:40 PM		EC-MoA-1 J. J. Thomson's Discovery of the Electron H.F. Dylla (Jefferson Lab) 1997 is the centennial of J. J. Thomson's "discovery" of the electron. On the evening of April 30, 1897 at a celebrated lecture given to the Royal Society, Thomson announced the results of three pivotal experiments on the conduction of electricity in gases that clearly distinguished "cathode rays" from the various phenomena that enlivened and complicated the observations of gas discharges in the 19th century. Thomson's experiments showed that cathode rays are comprised of a beam of negatively charged particles (which he called corpuscles) that had a mass-to-charge ratio approximately 1000 times smaller than the smallest known charge carrier, the hydrogen atom. Thomson's 1897 results built upon a series of experiments on gas discharges that he began in 1893 to compare and contrast the conductivity of gases with the analogous behavior in electrolytes, the latter phenomena being well described at the time by the works of Faraday, Clausius and Arrhenius. Despite encountering stiff competition to his notion that cathode rays are particulate, particularly from Hertz and Lenard who espoused a wavelike explanation, Thomson stuck with his hypothesis and eventually produced the crucial evidence to prove his hypothesis. In 1997 we honor both a great scientist and a great discovery that launched a full century of exploration of the subatomic world.
2:20 PM		EC-MoA-3 The Birth of Electronics:Thermionic Emission and Vacuum P.A. Redhead (National Research Council of Canada) The early developments of thermionic emission from 1880 until 1920 are reviewed with emphasis on the importance of vacuum technology in establishing the physical mechanism and in the production of reliable vacuum tubes. Edison in 1883 was the first to observe the passage of electricity from a heated filament in vacuum to a cold electrode, the so-called +Edison Effect¦, which was the birth of electronics. During the next fourteen years Fleming used a thermionic diode to rectify a.c., and it was shown that both thermionic emission and cathode rays carried a negative charge. In 1897 the electron was discovered by J.J.Thomson using a gas discharge source, in 1899 Thomson showed that a heated carbon cathode also produced electrons. There followed fifteen years of very active research on electron emission from hot cathodes in vacuum which resulted in a controversy between those who argued that the emission was the result of residual gases and chemical interactions at the cathode surface (zero emission in a good vacuum), and those who argued that the emission was a fundamental property of the cathode material (maximum emission in a good vacuum). The disagreement was finally resolved in 1913 by Langmuir and Richardson using improved vacuum techniques. In the same period the theories of thermionic emission and space charge were developed (Richardson, Child, Langmuir), and the emission properties of metal and oxide cathodes measured. From 1913 to 1920 the improved vacuum techniques developed by Langmuir and Dushman were used in thermionic emission measurements and in the commercial production of hot-cathode vacuum tubes.
3:00 PM		EC-MoA-5 Field Emission R. Gomer (University of Chicago) A brief explanation of field emission,and a short historical overview will be followed by a description of its principal applications, namely the field electron, field ion and scanning tunneling microscopes,and the use of field emission sources in electron optics.
3:40 PM		EC-MoA-7 A Brief History of Electron Diffraction M.G. Lagally (University of Wisconsin, Madison) Starting with the first discovery of electron diffraction by Davisson and Germer, I briefly trace the development of electron diffraction techniques as they relate to the interests of the American Vacuum Society, which are interpreted here to include the characterization of thin films and surfaces. Hence most of the emphasis will be on the development of low-energy electron diffraction and reflection high-energy electron diffraction. Where possible I will include the human side of this development rather than just the instrumental and scientific.
4:20 PM		EC-MoA-9 The Early History of the Three Element Vacuum Tube (1900 to 1920) D. Koijane, W. Jensby (Perham Foundation) The invention and development of the three element (triode) thermionic vacuum tube early in the century made possible the later establishment of a number of key industries and technologies. Among these are: Telephone, Radio, Radar, Television, Computers. The evolution of these and many other of our modern technologies would have been impossible without the existence of the vacuum tube. The whole concept of solid state electronics would have been inconceivable without the firm foundation that those early vacuum tube pioneers gave us. This session tells the story of the development of that foundation and the men who made it possible. The history of the early development of vacuum tubes is the story of brilliant and farsighted men who were unafraid to be pioneers. Their story has been told before but the pervasive influence of their work on our life today still isn't fully appreciated. The, sometimes rocky, path to the widespread use of electronics we have today often involved international controversies about prior discovery and patent rights. In fact, the early patent suits have become a source of developmental details for the historian. During his early work, J. A. Fleming, working in England, discovered that his tube, a diode referred to as a Fleming Valve, could detect radio waves. This led to the use of his tube by the Marconi Company, and the first production of tubes in quantity in 1905. Dr. Lee deForest carried on this work in this country, and in late 1906 added a grid to his diode, creating the triode, one of the most significant inventions of this century. DeForest called this tube, the Audion, and until 1915 all Audions were made by the H. W. McCandless Lamp Company in New York. The Audion was used initially as a detector in radio sets, and it was not until 1912 that deForest, working for the Federal Telegraph Co. in Palo Alto, California, invented the triode amplifier and oscillator. By 1915, other tubes were put on the market, such as the cylindrical three-electrode tube called the Audiotron, sold by E. T. Cunningham. Otis Moorhead and Elman Myers copied the Audiotron and sold them. All three infringed on prior patents. These are just some of the pioneers of this piece of history you will hear about in this session.