Title :
A high-efficiency quasi-optical mode converter for a 140-GHz 1-MW CW gyrotron
Author :
Thumm, Manfred ; Yang, Xiaokang ; Arnold, Andreas ; Dammertz, Guenter ; Michel, Georg ; Pretterebner, Julius ; Wagner, Dietmar
Author_Institution :
Inst. fur Hochleistungsimpuls-und Mikrowellentechnik, Karlsruhe, Germany
fDate :
5/1/2005 12:00:00 AM
Abstract :
A highly efficient quasi-optical mode converter system with several novel features has been designed and tested at Forschungszentrum Karlsruhe (FZK). The converter consists of a dimpled-wall waveguide launcher, one quasi-elliptical mirror and two toroidal mirrors. The coupled-mode theory has been used to analyze the operation of the prebunching waveguide launcher; the radiated fields from the cut of the launcher have been calculated by the scalar diffraction integral. Simulation results show that the advanced dimpled-wall launcher generates a well-focused Gaussian radiation pattern with low diffraction losses. In this case, toroidal mirrors are sufficient to obtain a desired output beam pattern. An efficiency of more than 98% has been achieved to convert the rotating TE28,8 cavity mode at 140 GHz into a fundamental Gaussian beam. Experimental measurements show close agreement with theoretical predictions.
Keywords :
Gaussian distribution; convertors; coupled mode analysis; gyrotrons; millimetre wave tubes; 1 MW; 140 GHz; CW gyrotron; Forschungszentrum Karlsruhe; Gaussian beam; Gaussian radiation pattern; coupled-mode theory; diffraction losses; quasi-elliptical mirror; quasi-optical mode converter; scalar diffraction integral; toroidal mirrors; wall perturbations; waveguide launcher; Diffraction; Gyrotrons; Heating; Mirrors; Optical waveguides; Planar waveguides; Plasma measurements; System testing; Tellurium; Waveguide theory; Coupled-mode theory; gyrotron; quasi-optical (QO) mode converter; wall perturbations;
Journal_Title :
Electron Devices, IEEE Transactions on
DOI :
10.1109/TED.2005.845791