NON-INCANDESCENT CATHODE OPERATION IN X-BAND MAGNETRON

K. Ilyenko, V.M. Gurdzhian, V.P. Dzyuba, T. Yatsenko

Abstract


A study of operation of non-incandescent cathode of X-band magnetron is reported, which employs field electron emission thin foil sharp blade-type sources to instigate the primary emission of electrons. We discuss conditions and practical considerations necessary to provide stable operation of the cathode.

The problem of engineering and manufacturing a reliable design of totally non-incandescent magnetron cathode turned out to be rather challenging: in the existing cathode-anode block configurations one needs to fulfil conditions for efficient FEE at a given operating level of applied A-K voltage (for non-relativistic magnetrons of the order of 10 kV for A-K gaps in the units of millimetres) and then ensure sufficient level of SEE to develop electron cloud capable of producing enough output magnetron microwave power. Moreover, introduction of thin foil sharp blade/knife-edge sources of FEE essentially into the A-K gap of a magnetron anode block should be done in a manner not disrupting electron cloud-anode slow-wave structure interaction resulting in production of microwave output power. Finding of appropriate engineering solutions to these goals is done on test A-K gaps at the design stage; however, in the manufactured packaged device, one can also trace evidence of described emission processes. Although there is no complete theory of a pre-oscillating dynamics of space-charge cloud in a magnetron, experimentally the leakage current provide a means of an insight into the development of electron cloud. The leakage current (as well as the back cathode bombardment) is a manifestation of a kind of nonlinear collective space-charge cloud oscillation in a non-neutral magnetically insulated electron plasma of the cloud. Accepting such a viewpoint, we can trace the onset of primary electron current as measurable anode leakage current in the pre-oscillating packaged magnetron. We can also experimentally observe the saturation of the FEE current as manifested by the saturation of the anode current before the start of microwave generation.

Key words: non-incandescent cathode, field and secondary electron emission, thin foil sharp blade field emitter, impregnated tungsten secondary emitter, X-band.


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DOI: http://dx.doi.org/10.30970/eli.27.11

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