P.D. Shalaev - Ph. D. (Eng.), JSC «SPE «Almaz» (Saratov). E-mail: p.d.shalaev@yandex.ru Yu.N. Scherbakov - Ph. D. (Phys.-Math.), JSC «SPE «Almaz» (Saratov). E-mail: scherbakov_yu@mail.ru

It is known that TWT life time with preservation of the set parameters is limited with a cathode life time. At irregular electron current density distribution (emission density) its operation temperature raises for provide cathode work in the mode of current restriction by a space charge on the sites with the maximum emission density. Therefore, to increase a TWT life time, it is necessary to obtain un-iformity of current emission density on the cathode. Researches of current emission density distribution on a cathode surface depending on a relative dislocation of potential surfaces and on potential values on them in axisymmetric guns are carried out by means of the developed analysis program of the axisymmetric electron-optical systems (EOS) FENIX-EOS. The program provides to simulate EOS (including gun and collector assemblies) on the basis of the finite elements method. The self-agreed iterative decision of trajectory analysis and an electrostatics is carried out. The electron beam is simulated by a set of large particles. The equation of the movement is presented in paraxial approach. Emission current from the cathode is limited by a space charge. Thermal speeds of the emitted electrons are accounted according to the law of a cosine with casual selection. The program has a graphic editor, a block of an automatic input of magnetic field in regular part and semi-automatic reader of measured graphic longitudinal components of a magnetic field induction. The results of researches are illustrated on graphics of current density distribution along the cathode radius depending on the potential values of the focusing electrode, on the value of deepening of the cathode in the focusing electrode, and on the spherical radius of the cathode. Also the results of optimization of EOS of Ku-range TWT at the maximum slope angles of electronic trajectories are given. It is shown that emission density irregularity along cathode radius may exceed 50% under a non-optimal combination of the focusing electrode potential, the sizes and a relative dislocation of electrodes of the gun. The results show, it is possible to achieve uniform emission density distribution from the cathode surface by optimization of both the design and electrode potentials of the gun. It will be possible to increase cathode life time the same with TWT under all other equal conditions.

 

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