Effects of diode gap closure and bipolar flow on vircator microwave generation

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Title: Effects of diode gap closure and bipolar flow on vircator microwave generation
Author: Young, Douglas T
Abstract: High power microwaves are useful in a wide variety of applications in science , industry and in the military . The virtual cathode oscillator , or vircator , has been seen to produce very high output power over a widely tunable range compared with other high power microwave sources . Many experiments and numerical simulations have been done to study various aspects of vircators and the radiation produced by them . Two effects which have not been previously studied are the effects of diode gap closure and bipolar flow on the microwave radiation produced in vircators . In this work , these effects are studied using the PIC code MAGIC . One - and two -dimensional diode simulations agree well with known analytical results formulated for these diode cases . In both one - and two -dimensional vircator simulations , diode gap closure and bipolar flow were studied in detail . The geometry used in the two -dimensional vircator was made to be similar to that of an experiment done at the Himeji Institute of Technology in Japan . This was done so that comparisons between the simulations and an actual experiment could be made . The primary conclusion of this thesis is that neither bipolar flow alone nor diode gap closure alone can generate electron beam pinching in a two -dimensional vircator in which the experiment did show electron beam pinching . The second conclusion that is drawn in this work is that diode gap closure is the mechanism that allows vircators to achieve higher output powers . Finally , comparisons between the one - and two -dimensional vircators with diode gap closure or bipolar flow show a dramatic difference in the frequency spectrum of the output microwaves . Suggestions for further work , which include the creation of a model which combines both diode gap closure and bipolar flow , are also included .
URI: http : / /hdl .handle .net /2346 /9157
Date: 1996-05

Citation

Young, Douglas T Effects of diode gap closure and bipolar flow on vircator microwave generation. Master's thesis, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /9157 .

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