This thesis is concerned with a study and evaluation of the use of ferrites to produce non-reciprocal attenuation in slow-wave structures for high-power travelling-wave amplifiers. Two structures' are investigated in detail, one suitable for a high-power "0"-type amplifier, the other for a high-power "M"-type amplifier. The "0"-type amplifier structure investigated is the folded waveguide. Not only is this structure eminently suitable for high-power applications, but it is a relatively easy matter to achieve non-reciprocal attenuation in it by means of rectangular waveguide-typeisolators. As a result, the folded-waveguide has been'the subject of two previous and independent investigations. In each case a theory of the folded-waveguide was developed and a non-reciprocal structure was constructed. Although the two theories are identical, the non-reciprocal structures built differ considerably. One structure was for c.w. operation at X-band with an 11 watt beam, the other for pulsed operation at S-band with a 0.8 megawatt beam. In neither case was the structure, with or without ferrites, tested in a working amplifier. The work on the folded-waveguide structure described here is a continuation of that which led to the development of the non-reciprocal X-band structure. The design, construction and performance of an electron gun for this structure are described, and the results of "0"-type amplifier measurements on it are given. Although the design gain of the tube was 15db., no amplification was obtained. The failure of the tube to amplify is discussed. It is shown that this was due to a design fault. By neglecting to take into account space charge debunching of the electron beam, the structure had been designed with too low a coupling impedance. A detailed analysis of the folded-waveguide structure and ways of producing non-reciprocal attenuation in it follows. It is concluded that, in general, when the structure is designed so as to be suitable for amplifier operation, it is no longer possible to incorporate rectangular waveguide-type isolators in it. The "M'-type amplifier structure investigated is the ridge loaded ladder line. The basic theory of the structure is given, and the results of dispersion, coupling impedance and "0"-type amplifier measurements on an X-band circuit are presented. The design of an "M"-type amplifier making use of this circuit is then described and predicted performance figures for it are given. The development of a non-reciprocal attenuator system for this tube is discussed, and the results of measurements on the non-reciprocal structure are presented and evaluated. It remains for the structure to be tested in a working "M"-type amplifier.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:602189 |
| Date | January 1963 |
| Creators | Elliott, John |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/13229 |
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