TRAVELLING WAVE TUBES

摘要

Improvements in or Relating to Travelling Wave Tubes The invention provides a travelling wave tube having a directly heated cathode. Cathode material is applied in a depression in one U-shaped member of a high resistance alloy material whilst the return path for heater current is provided by another U-shaped strip member beneath the first. The configurations of the two strip members are similar so that stray magnetic fields generated by the equal but opposite currents flowing therein, tend to neutralise one another. In another embodiment the two strip members are replaced by generally cylindrical members, one member being within the other. The surface of the member providing the return path for heater current is polished where it faces the member carrying the cathode material so as to reflect back heat radiated by the lastmentioned.