THE NUMERICAL MODELLING OF DYNAMIC PROCESSES IN AUTOPHASE ELECTRON BEAMS

The article looks into dynamic processes in an autophase TWT in the mood of back energy transformation on the basis of a 3-D numerical model. It has been shown that the mood of back energy transformation is characterized by the dependence of the electron wave interaction on the stable capture mood of an electron beam by the HF-field. The analysis of dynamic defocusing in autophase TWT in the mood of back energy transformation was studied. The defocusing of the electron flow in the dynamic mood is characterized firstly by the increasing field of the space charge density in the capture bunch, and next is radial and azimuth spiral field. The latter’s begin to act in the autophase section exit when many electrons exit the capture and partly defocusing of the electron flow takes place under field of the space charge action leading to the local current subsidence. The mechanism of the maximum transformation HF-power achievement is accompanied by gradual potential well shoaling and the bunch breakup.The potential well shoaling to a critical level takes place at significant residual values of the input HF-power.The current subsidence takes place in local regions and it is determined by uncaptured electrons and capture leaving particles. The essential unlaminarity of the electron flow rises the current subsidence on the RS and together with the capture violation decreases the device efficiency. The analysis of phase diagrams makes it possible to monitor the evolution of an electron bunch capture up to its destruction and to allocate the wave length field of an autophase section where the process of energy transformation is still taking place.

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