TWT Theory Research Articles

To the theory of induced scattering of electromagnetic waves by an electron beam in a regular waveguide

In this work, a formula for the amplification parameter (analogous to the Pierce parameter in travelling-wave tube theory) of regular waveguide modes is deduced in the case of induced scattering by an electron beam with an arbitrary electron density distribution in the cross section. The presence of an axial magnetic field transporting a beam along the interaction region is taken into account. Obtained results can be used for calculation of the amplification in free electron lasers with electromagnetic, magnetostatic or electrostatic pump and a definite beam transverse profile. In particular, expressions for amplification coefficients in the case of a thin-wall hollow electron beam propagating in a cylindrical waveguide, that takes into account the excitation of beam waves (space charge in TWT theory), are found. An analysis of the dependence of amplification on the guiding magnetic field value and hollow beam radius is carried out.

A high-power, traveling wave tube amplifier

High-power X-band traveling-wave tube amplifiers (TWTs) have been fabricated and tested. The tubes have gains ranging from 13 to 35 dB at 8.76 GHz and output powers ranging from 3 to 100 MW. The amplifiers are driven by the interaction of a slow space-charge wave, propagating on an electron beam, with an electromagnetic wave supported by the structure. The electron beam, which is produced from a magnetic-field-immersed field-emission cathode, has an energy of 850 keV, a current in the 1-kA range, and a pulse duration of 100 ns. The amplifiers are designed to operate as narrow-band devices in the TM/sub 01/ mode. A report is presented on the amplifier characteristics, and their performance is compared with calculated performance using conventional TWT theory. The scaling of the gain and bandwidth with the beam current are approximately as expected from theory, but the absolute magnitude of the gain is somewhat greater than expected.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Taking into account dissipation in the wave theory of TWT operating at the limit of the transmission band

Taking into account dissipation in the wave theory of TWT operating at the limit of the transmission band

Two-conductor strips with drift tubes excited by an electron beam in an ion accelerator

Excitation by a heavy-current electron beam in an ion accelerator is studied for a two-conductor strip with drift tubes whose supports on one bar are displaced at half the distance between the supports of another bar. The relations obtained on the basis of harmonic analysis and the equations from TWT theory indicate the potential of constructing such a system.

Doppler shifted cyclotron generation of exospheric very-low-frequency noise (“HISS”)

Abstract Cyclotron radiation from a receding electron in the exosphere can be doppler shifted to a frequency much less than the local gyrofrequency. A discrete bunch of electrons will produce a discrete emission as shown previously. (1) A stream of electrons will produce band limited white noise or hiss. The low frequency limit of this band is an emission cut off and the upper limit is a propagation cut off. Narrow, wide and very wide bands of hiss can be produced by electron streams of even very broad velocity and pitch distribution. Tests of this theory and of the TWT theory (2) are suggested.