Effect of the Ion Background on the Characteristics of the Output Signal from the Oscillator with the Turbulent Electron Beam

Abstract

One of the promising directions in modern vacuum electronics is development of devices based on complex dynamics of a nonlaminar electron flux [1]. The dynamics of such nonlaminar electron flux explains the distinct noiselike character of the output signal spectrum observed in experiments [2]. One of the key problems that strongly limits the area of application of oscillators with turbulent electron beams and is most difficult to solve is high irregularity of the output signal spectrum [2]. Among the main factors affecting formation of bunches in a electron beam, in addition to the factors directly governing the conditions for beam formation by the electron gun (convergence angle, perveance) and factors affecting the electron beam as it moves in the drift region (magnetic field shape and configuration, retarding potential), are residual gas ions [3]. We have shown that changing the conditions for formation of electron bunches (the effect of the residual gas pressure) in the turbulent beam can appreciably affect the output characteristics of the device [4]. It is shown that ions resulting from gas ionization in the drift region promote formation of denser and more compact space charge bunches. It was also shown that denser bunches increase the output signal power and aid in appearance of higher-order components in the spectrum, thus extending the working range to a higher-frequency region. When the device operates in the regime of noiselike signal generation, ions contribute to a decrease in the irregularity of the output power spectrum to about 0.3 dB in the working frequency range up to two octaves.