A model for quick thermal prediction of multi-stage depressed collector

Abstract

Multi-stage depressed collectors (MDCs) aid in efficiency enhancement of travelling-wave tubes (TWTs) by recovering the unused energy from the spent electron beam. Evaluation of the thermal performance of a MDC is crucial for an optimal design. Although several commercial software tools are readily available for performing the thermal analysis, (1) they are time-consuming and (2) the final results depend largely on few critical parameters (like thermal contact resistances at various joints, convection heat transfer coefficient, etc.). Hence, here a simple analytical model has been developed for quick prediction of the worst-case thermal behaviour of the MDC. Brazing non-uniformities that arise in any practical scenario have been taken into consideration in terms of their thermal contact resistances. Moreover, any cooling mechanism used, either convection or radiation, can also be correspondingly incorporated. Analytical results obtained from the model have been validated with simulated and experimental results. This model also aids in accurate calculation of few vital input parameters required for performing simulation with commercial software tools.

Keywords:

• Multi-stage depressed collectors
• traveling-wave tube
• thermal analysis
• thermal contact resistance
• analytical model
• radiation
• convection

Acknowledgements

Authors are thankful to Director, CSIR-CEERI, Pilani for his kind permission to publish this work. Authors are also thankful to TWT team members for their support, cooperation and time-to-time suggestions for the improvement of the work.