Average power limits of brazed-helix TWT´s

Over the past 15 years, THOMSON-CSF has developed and perfected a specific technology for making brazed-helix traveling-wave tubes (TWT´s), which has made it possible to reach output-power levels previously unattainable with helix TWT´s. This technology has been applied to produce a large family of such TWT´s, covering the range of frequencies from 2 to 18 GHz After recalling the main features of this technology, a thermal analysis and the results of a series of experiments are given. For example, an RF power of 2 kW CW was injected into a brazed-helix slow-wave structure section identical to that of a 14-GHz TWT, without either destroying or irreversibly modifying it. Finally the factors currently limiting the average power capabilities of brazed-helix TWT´s are analyzed and the possibilities for extending these capabilities discussed. A graph showing the ultimate power limits of the technology is given.