Effect Of Velocity Spread Research Articles

Effect of velocity spread on finite-length free electron laser gain

A theory of general stimulated backscattering by a hot, relativistic electron beam propagating through a spatially periodic, transverse magnetostatic field is presented. The electrons are chosen to have a Lorentzian distribution in velocity space. Though energy spread acts to diminish gain, its effect is negligible if Δγ/γ < < N-1, where N is the number of undulator periods. The analysis is linear and applicable to both the single-particle and collective regimes.

Solitons and non-linear gyro-TWT theory

A description of two new approaches to non-linear gyro-TWT theory is given. Both approaches are based upon the soliton concept. A soliton is a solitary wave in a non-linear, dispersive medium where the non-linearity and dispersion counteract each other to prevent, wave break up. The application of tile soliton concept to microwave, crossed-field amplifiers (i.e., the applied DC magnetic and electric fields arc perpendicular) has shown great success. Close agreement between theory and experiment has been demonstrated. This success is the motivation for applying the soliton concept to gyro-TWT's, The first approach is a non-linear, coupled-mode theory. Only a brief discussion is given. The second approach differs from the first in that the coupling between modes is assumed strong with a weak non-linearity. A non-linear, partial differential equation is derived and solved for soliton solutions. Amplification regimes are discussed as well as saturation mechanism. Velocity spread effects are briefly analysed by using a different analytic approach.

Gyrotron travelling wave amplifier: II. Effects of velocity spread and wall resistivity

The small signal gain and bandwidth of the gyrotron travelling-wave amplifier (gyro-TWA) operating at the fundamental cyclotron harmonic are examined. The analytical and numerical studies focus on the effects of velocity spread in the electron beam and of a distributed wall resistivity in the waveguide. It is found that wall resistivity reduces the forward gain of the amplifier only by an amount approximately equal to 1/3 of the corresponding cold tube loss. Significant increase in bandwidth may result, under certain conditions, from the presence of wall resistivity. A moderate amount (5–10%) of velocity spread does not reduce the peak gain significantly in general, but may reduce the bandwidth by an amount depending on the applied magnetic field. Based on considerations of such factors as power, stability, gain, bandwidth, and efficiency, operating parameters for the gyro-TWA are suggested.

Influence of velocity spread on gain and efficiency of klystrons

This paper presents the calculation of the effect of velocity spread in electron streams on the gain and efficiency in klystrons. Using the density-function method and assuming a half-Maxwellian velocity distribution, a small-signal theory of a klystron tube was developed. The form of the solution is a power series whose coefficients contain even powers of ω q/ω. The effect of losses in the cavity has also been included. The results are presented as plots of the ratios of the ac component of the bunched current with velocity spread vs a dimensionless parameter that is a measure of the velocity spread. The plots contain ωq/ω, the lengths of the drift tube and of the gaps as important design parameters.