Design of a simplified electron gun without BFE for linear beam tubes

Suneeta Arya, Atmakuru Nagaraju, and Sanjay Kumar Ghosh
Central Electronics Engineering Research Institute, CSIR, Pilani, Rajasthan- 333 031
Dedicated to Prof B N Basu

Design and realization of electron gun for high frequency helix traveling-wave tubes (TWTs) with enhanced current density remained a challenging task. In conventional multi-electrode electron gun geometry, both radial and axial positions of electrodes (namely, beam focus electrode (BFE) and various anodes) with respect to the cathode are the key parameters for controlling the electron beam optics. In particular, geometry and position of BFE with respect to the cathode are very complex and sensitive. To avoid such complexity, a simple electron gun, without BFE, has been designed and proposed in this paper. In the proposed design, the BFE has been replaced with a simple geometry anode, which plays important role in controlling beam optics and subsequent enhancement of the beam current. Proposed method eliminates the use of a BFE having complex geometry and also the complexity of maintaining its critical axial and radial distances with respect to the cathode. These two improvements make the electron gun assembly simple and straightforward. The proposed electron gun has been modelled in commercial simulation codes EGUN and CST Studio and compared against a practical conventional gun as a special case. © Anita Publications. All rights reserved.
Keywords: Traveling wave tube (TWT), Electron gun, Parametric analysis.

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