Copyright 1997 IEEE. Reprinted with permission from the IEEE publication, “Scanning the Past” which covers a reprint of an article appearing in the Proceedings of the IEEE Vol. 85, No. 2, February 1997.
Rudolf Kompfner and the Traveling-Wave TYibe
Fifty years ago this month, the PROCEEDINGS OF THE RADIO ENGINEERS (IRE) included a paper by Rudolf Kompfner (see Fig. 1) on the traveling-wave tube as a microwave amplifier. At the time he was affiliated with the Clarendon Laboratory of Oxford University in England. He received the IEEE Medal of Honor in 1973 as recognition of having made “a major contribution to worldwide communication through the conception of the traveling-wave tube embodying a new principle of amplification.” He also made significant contributions to the development of communication using earth satellites.
Kompfner was born in Vienna, Austria, in 1909. He graduated with a degree in architecture from the Technische Hochschule in Vienna in 1933. In 1934, he moved to England, where he worked as an architect and developed a vocational interest in radio and electronic tubes. He took advantage of the facilities available at the Patent Office Library and began to write for radio journals in his spare time. After the outbreak of World War II in 1939, he was interned as an alien on the Isle of Man but was released in 1941 to join the staff of an advanced electronics laboratory at the University of Birmingham. The laboratory was directed by Mark L. Oliphant and was the site of the demonstration of the resonant cavity magnetron as a high-power microwave generator by Henry A. H. Boot and John T. Randall early in 1940.
Assigned to work on development of a klystron amplifier, Kompfner determined that the coupling between the radio frequency field in resonator gaps and the electron beam was too weak to give suitable results. In the fall of 1942 he came up with the idea of creating an interaction between a traveling electromagnetic wave and an electron beam. In a notebook entry dated November 12, 1942, he mentioned “a completely untuned amplifier” and his sketch showed a helix between the input signal and output (see Fig. 2). For a time he called it a “helical coaxial-line amplifier.” Several colleagues left the laboratory to take up research related to atomic bombs, but Kompfner continued to work on the traveling wave concept as “spare-time amusement” from his principal assignment of klystrons. He obtained amplifi¬cation (see Fig. 3) for the first time with an experimental traveling-wave tube (Fig. 4) on November 1, 1943. In 1944, he was transferred to the Clarendon Laboratory at Oxford where he and Joseph Hatton, a research assistant, continued theoretical and experimental research on the new device. They shared their findings with John R. Pierce of the Bell Telephone Laboratories who visited Oxford in 1944 and who soon produced a more elegant theory of traveling-wave tubes.
Information about the research on traveling-wave tubes remained secret until June 1946 when Joseph Hatton pre¬sented a paper about it at an electron tube conference at Yale University. More complete information was provided by Kompfner’s paper in the February 1947 issue of the PROCEEDINGS and two papers by Pierce (one with L. M. Field as coauthor) in the same issue. Pierce’s book Traveling-Wave Tubes was published in 1950. Kompfner received a doctorate in physics from Oxford in 1951 and joined Pierce’s group at the Bell Laboratories the same year. Continuing work he had started in England, Kompfner developed a backward-wave oscillator and amplifier which could be tuned electronically. He disclosed this discovery at a tube conference in Ottawa, Canada, in June 1952.
Kompfner began theoretical work on earth satellite com-munication by 1958 and published a joint paper with Pierce in the March 1959 PROCEEDINGS OF THE IRE, entitled ‘Transoceanic Communication by Means of Satellites.” They considered both passive and active satellites and concluded that they had “a great deal of confidence in the overall feasibility of satellite communications.” Their work contributed to such early projects as the passive satellite Echo launched in 1960 and the active repeater satellite Telstar in 1962.
Kompfner retired from Bell Laboratories and subse¬quently taught at Stanford University and at Oxford. He was elected to both the National Academy of Sciences and the National Academy of Engineering. His book The Invention of the Traveling-Wave Tube was published by San Francisco Press in 1964. His colleague John Pierce wrote that the book “can tell you something of the strange and wonderful ways in which important inventions and discoveries are actually made.”
Kompfner died in December 1977 at age 68.
 IEEE Center for the History of Electrical Engineering.  R. Kompfner, The Invention of the Traveling Wave Tube. San Francisco: San Francisco Press, 1964.
James E. Brittain