Comparison between one and two dimensional models of coupled cavity TWT performance

Coupled cavity TWT performance has been modeled using 1D (CHIRISTINE-CC) and 2D (TESLA-CC) approaches. The codes´ predictions have been compared in detail for regimes for which application of both codes is valid. It was found that the level of code agreement depends primarily on beam current (beam perveance). The codes predict almost identical gain for the small current regime while differences in gain might reach 10% for high perveance CC-TWTs. The main reason for these differences is non-uniformity in distribution of the RF field associated with the bunched beam. RF space charge effects together with the focusing magnetic fields are major sources of differences between predictions of 1D and 2D codes, while other 2D effects make small contributions.