INFLUENCE OF THE ACCELERATING POTENTIAL PULSE FORM ON THE PROPERTIES OF THE HELICAL ELECTRON BEAM IN GYRO-DEVICES

摘要

The efficiency of powerful gyro-devices strongly depends on the quality of Helical Electron Beams (HEBs) used as an active media for RF generation. The most popular system to form HEB is the magnetron-injection gun (MIG). In MIGs one of the most important factors influencing on the quality of HEBs is the reflection of particles from the magnetic mirror near the cavity [1]. Such particles are accumulated in the adiabatic trap between cathode and cavity, make worse beam quality and can initiate the beam instability in regimes with big pitch-factor. Usually numerical simulation of particle's accumulation process is performed within the simplest assumption that the pulse has the form of the "step" and the current density and accelerating voltage are established instantly [2]. But real pulse front duration in gyro-devices is much longer than the period of oscillations of particles in the trap (at least in one or two orders). So, in principle, one can expect that the "history" of real growing of the accelerating voltage U(t) may influence on the beam behavior and final beam properties as well. Besides that, momentary switching on the voltage leads to such well-known effect, as the accelerating of the "head" of the beam. Accelerated particles also may change the conditions to catch electrons into adiabatic trap in comparison with situation of smooth increasing of potential. Below the investigation of the influence of the pulse form U(t) on the establishing process in HEB a performed. The case when HEB has big pitch-factor and so trapped electrons influence on the beam parameters essentially is considered.