Thermal and structural analyses of the multistage depressed collector of a traveling wave tube

The traveling wave tube (TWT) is often used as a power amplifier in various applications such as broadcasting, radar and space communications. For an efficient performance of a TWT, it requires an optimal design and thorough analysis of every element in the TWT. In this work, a steady state thermal and structural analysis of the collector portion of TWT using a commercial finite element code, ANSYS 7.0, is performed. The collector portion of TWT is chosen, as two-thirds of the heat dissipation occurs in this region. Electromagnetic data obtained from MICHELLE®, a collector modeling tool, are mapped and interfaced with the ANSYS load data. The mesh generated using ANSYS ICEM CFD 11.0 is used by the preprocessors of MICHELLE® and ANSYS 7.0. A ceramic insulator is modeled and mated using the contact elements with the imported mesh model of the collector. Suitable materials for the collector sleeve are also analyzed. The effect of brazing technique on the model is studied and demonstrated by varying the thermal contact conductance between the collector electrodes and the ceramic insulator. The collector model is analyzed for best case and worst case scenarios of electron distribution. Analysis results indicate that a maximum temperature of 74.8°C and a maximum stress of 175.9 MPa occur in the inner region of the collector electrodes for the best case scenario. The results show that the proposed design is well within the safety limits. A major portion of this work can be contributed towards the path chosen in mapping the MICHELLE1* output data with the ANSYS load input data. The present study also focuses on the challenges encountered at various stages starting from the preprocessor stage of mesh optimization to the postprocessor stage of analyzing the collector results. In this work, an appropriate fin design for the collector model has been proposed.