Efficiency increase in a traveling wave tube by tapering the phase velocity of the wave

Levi Schaechter; John A. Nation

doi:10.1117/12.43479

1 April 1991 Efficiency increase in a traveling wave tube by tapering the phase velocity of the wave

Levi Schaechter, John A. Nation

Proceedings Volume 1407, Intense Microwave and Particle Beams II; (1991) https://doi.org/10.1117/12.43479
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

The beam-wave interaction in a Cerenkov traveling wave tube is considered theoretically. The system is assumed to operate at 8.75 GHz either as an amplifier or as an accelerator. The injected electrons have a kinetic energy of 0.85 MeV and the beam at the entrance can be prebunched or uniform. To avoid saturation, two kinds of tapering are considered: one which is adaptable, in the sense that the phase velocity follows exactly the particle's velocity; in the other, the dielectric coefficient varies algebraically in space. In the case of an accelerator (Eo equals 5 MV/m, I equals 1 A and d equals 0.8 m) the adaptable tapering causes the system to be almost three times more effective than in a uniform device. An analytical solution corresponding to the case 2(gamma) (r)(2) >> 1, is discussed. The other case considered is when the injected beam has a uniform distribution of phases relative to the wave. The construction of the bunching is illustrated as well as the regime in which the amplitude of the wave increases linearly; our simulation reveals that almost 50% of the interaction region is exploited for the former process. The authors show that by tapering, both the gain and the efficiency increase. When operated as an amplifier (E0 equals 1.0 MV/m, I equals 450 A and d equals 0.3 m) with an optimal linear variation of the dielectric coefficient, the efficiency is improved to about 30% from the 5% in the uniform device.

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Levi Schaechter and John A. Nation "Efficiency increase in a traveling wave tube by tapering the phase velocity of the wave", Proc. SPIE 1407, Intense Microwave and Particle Beams II, (1 April 1991); https://doi.org/10.1117/12.43479

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KEYWORDS

Electrons

Amplifiers

Particles

Dielectrics

Microwave radiation

Phase velocity

Particle beams

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