Limitation of cross-excitation instability in a relativistic Cerenkov generator with coaxial slow wave structure

The operation in the cross-excitation instability regimes for relativistic backward wave oscillators has been reported and studied in some earlier papers. In the experiment of a relativistic Cerenkov generator with coaxial slow wave structure (CRCG), the cross-excitation instability has also been observed by us. In this paper, experimental results for the CRCG operating in this regime are given, and an explanation is provided to account for the appearance of the instability. Based on this explanation, two types of reflectors, i.e., coaxial Bragg reflectors and cutoff necks, are adopted to restrain the cross-excitation instability by increasing the reflection coefficient at the entrance of the coaxial slow wave structure.