Chaotic generation in a megawatt backward-wave tube

Experimental and theoretical studies on the self-modulation mode of generat ion in a high-power BWT with the electrodynamic system representing a sligh tly corrugated waveguide are presented. The BWT is fed by an electron beam with the energy 150 keV and the current 150 A. The system operates at the E -01 mode with the mean frequency 8.7 GHz. Dynamic chaos is obtained by a th ree-fold increase in the length of the interaction space in comparison with the prototype exhibiting stationary generation. The stationary generation was changed to periodic sinusoidal self-modulation and then to chaotic self -modulation as the current increases from 6 to 60 A. The generation mode is simplified when the current ranges from 70 to 90 A and becomes complicated again for the current exceeding 100 A. Experimental observations are in go od agreement with the results of simulation predicting a certain simplifica tion of the self-modulation mode at the currents 70-90 A owing to the effec t of high-frequency space charge. Under the conditions of chaotic generatio n, the mean power was as high as 2 MW at the relative spectral width of the signal 4% and the total duration of the microwave pulse 10 mus. (C) 2001 M AIK "Nauka/ Interperiodica".