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Published December 1961 | public
Journal Article Open

Interaction of a Modulated Electron Beam with a Plasma


The results of a theoretical and experimental investigation of the high-frequency interaction of an electron beam with a plasma are reported. An electron beam, modulated at a microwave frequency, passes through a uniform region of a mercury arc discharge after which it is demodulated. Exponentially growing wave amplification along the electron beam was experimentally observed for the first time at a microwave frequency equal to the plasma frequency. Approximate theories of the effects of 1) plasma-electron collision frequencies, 2) plasma-electron thermal velocities and 3) finite beam diameter, are given. In a second experiment the interaction between a modulated electron beam and a slow electrostatic wave on a plasma column has been studied. A strong interaction occurs when the velocity of the electron beam is approximately equal to the velocity of the wave and the interaction is essentially the same as that which occurs in traveling-wave amplifiers, except that here the plasma colum replaces the usual helical slow-wave circuit. The theory predicting rates of growth is presented and compared with the experimental results.

Additional Information

© 1961 IEEE. Reprinted with permission. Received by the IRE, August 7, 1961. This work was supported by the Office of Naval Research, Contract NONR 220(13). A great deal of credit for the success of these experiments is attributable to A.F. Carpenter, whose skill and patience in the fabrication of the glass tubes is gratefully acknowledged. Fruitful discussions were enjoyed with Dr. A.W. Trivelpiece. The continuing support of the Office of Naval Research is very gratefully acknowledged.

Attached Files

Published - BOYprocire61.pdf

Accepted Version - TR000358.pdf


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August 21, 2023
August 21, 2023