Crossed-Field Reentrant Stream Tandem Slow-Wave Circuit Tube

摘要

1,155,673. Travelling-wave tubes. S-F-D LABORATORIES Inc. 23 May, 1967 [13 June, 1966], No. 23977/67. Heading H1D. A crossed field reentrant-stream discharge tube having a coaxial cathode and anode and an axial magnetic field for producing circulation of the electron stream round the cathode in a predetermined direction, includes a pair of backward-wave slow-wave structures 18, 19 extending in series circumferentially around the cathode for interaction between the electron stream and wave energy on the slow-wave structures propagating counter to the predetermined direction, one of the slow-wave structures 18 serving to bunch the stream with signal energy to be amplified from driver tube 11, and having its downstream end 8 disposed sufficiently close to the upstream end 9 of the other slowwave structure 19, which constitutes the output circuit for the bunched stream to excite the latter. The arrangement effectively isolates the buncher section from energy reflected from the load 13, which energy is absorbed by a non- reflective load 24 provided at the downstream end 23 of the output section. The drift space 22 corresponding to the sever 21 between output and buncher sections is less than 3 times, and preferably of the order of, a space charge wavelength, while the drift space 27 corresponding to the sever 25 between the two sections may either be long enough to permit the beam effectively to debunch, or may be as short as drift space 22 (Fig. 8, not shown), such that positive feedback is provided to give a narrow band tube which may be provided with a fixed anode-to-cathode voltage and controlled by a control electrode which is pulsed positive, to collect the electron stream and prevent further operation, upon the cessation of the input signal pulse from the driver tube. The buncher section is itself provided with a non-reflective load 28 at its upstream end 26. In a modified tube (Fig. 9, not shown), the cathode is split into two insulated sectors co-extensive with the buncher and the output sections, respectively, permitting operation at increased efficiency by the application of different potentials to the two sectors, and the use of the sector corresponding to the buncher as a control electrode for turning off the tube. Use of the tube as an oscillator, by feeding a fraction of the output through a directional power splitter and variable phase shifter to the buncher section (Fig. 12, not shown), and an amplifier formed by a chain of tubes having their buncher sections connected in series (Fig. 13, not shown) or in parallel to the driver tube (Fig. 14, not shown) are described.