Present status of a 17.1-GHz four-cavity frequency-doubling coaxialgyroklystron design

A design of a Ku-band 17.1-GHz four-cavity coaxial gyroklystron amplifier for driving future linear colliders is presented. The X-band input cavity operates in the TE_0.11 mode, whereas the remaining three cavities (buncher, penultimate, and output) operate in the TE₀₂₁ mode, doubling the frequency of the input signal. The electron beam parameters are the following: current of 540 A, voltage of 460 kV, perpendicular-to-parallel velocity ratio of 1.5, and a parallel velocity spread of 6.4%. The output cavity has been simulated as (1) zero-drive unstable with Q-factor of 320 and (2) zero-drive stable with Q-factor of 250. The simulations show that the maximum efficiency in the first case is 37.4%, and in the second one is 34.4%. In both cases, a high gain of 60 dB at a 100-MW output power level can be realized     

Theory of gyrotwystrons with mixed transverse geometries of thevarious stages

Gyrotwystrons are gyrotron amplifiers with resonant cavities, field free drift regions, and a nonresonant output waveguide. They are expected to be more wideband than gyroklystrons, and more efficient than gyro-travelling wave tubes. A theory of gyrotwystrons has been developed which describes gyrotwystrons with cavities of different transverse geometry than the output waveguide. An analytical approach permits one to estimate in a simple manner the effect of mixed transverse geometry on the interaction between the electron beam and the microwave field. Numerical studies of an NRL gyrotwystron design show it possible to realize a rather high efficiency over a large bandwidth (e,g., 35% efficiency with a bandwidth of 6%)     

Theory of gyro-backward wave oscillators with tapered magneticfield and waveguide cross section

A theory is developed which describes gyro-backward wave oscillators (gyro-BWO's) with arbitrarily relativistic electron beams and tapered external magnetic field and waveguide wall radius. For the case of linear tapering the optimal parameters are found that correspond to highly efficient operation. The frequency tunability as the function of magnetic field and voltage deviations has been analyzed. It is shown how to use the results given in terms of normalized parameters for designing concrete gyro-BWO's. For one concrete design the effect of electron velocity spread on the efficiency has been studied     

Temporal evolution of electron beam transport in PASOTRON microwavesources

The plasma-assisted slow-wave oscillator (PASOTRON) is a high-power microwave source, in which the transport of an intense electron beam through an interaction region is based on the focusing effect of a beam generated plasma channel (Bennett pinch). A simple theory is developed which describes the self-consistent nonstationary processes of the plasma formation due to impact ionization of an axially inhomogeneous gas by the beam and the beam focusing effect of the plasma. The theory is illustrated by examples showing the temporal evolution of the beam transport in the process of plasma creation in PASOTRONs