G.A. Azov - Ph. D. (Eng.), Head of Department, JSC «Pluton» (Moscow). E-mail: g.azov@pluton.msk.ru
E.R. Ganeev - Leading Engineer, JSC «Pluton» (Moscow). E-mail: g.azov@pluton.msk.ru

During production of the TWT model UV 523 and its further tests in specific electronic devices we found that a significant proportion of these devices had parasitic oscillations in the output spectrum, and that the relative level of parasitic oscillations in the operating frequency of the TWT could be as high as −20 dB or greater, which made the products unusable. It turned out that these parasitic oscillations were caused by excessive electron backflow from the two-stage collector into the interaction space. Experiments and calculations showed that an increase in the magnetic induction generated by the first and the second magnets of the collector part of the periodic magnetic focusing system of TWT UV 523 significantly reduces the electron backflow, which reduces the anode current and eliminates the conditions for appearance of parasitic oscillations. We developed specifications for the magnets of the collector part of the focusing system and for the anode current to ensure an acceptable relative rate of parasitic oscillations. Measurements of the output spectrum of 165 TWT UV 523 units manufactured in accordance with these specifications showed that in none of them the relative rate of parasitic oscillations exceeded −40 dB during signal amplification over the entire operating frequency range.