HEAT TRANSFER AND POWER CAPABILITIES OF EHF HELIX TWT'S.

Abstract

The heat transfer capability of the helix is the primary factor which determines average output power capability of a travelling-wave tube (TWT). Thus, for maximum power capability in an EHF helix TWT, it is necessary to maximize thermal conduction from the helix to the external enclosure and to minimize the beam interception and RF loss. The authors have performed experiments with several different types of helix assembly methods in both the brazed and the compressed categories, and have chosen the wire wrapped compressed helix assembly structure for use in high power EHF helix TWTs. The results have been good, and respectable power dissipation capabilities have been obtained. The key is the ability to accurately control the pressure applied at each helix turn to support rod interface so that uniformly low thermal interface resistances are obtained.