Modeling Stability of Vacuum Electronic Devices With the Large-Signal Code TESLA-Z

We present a new approach to the study of the stability of Vacuum Electronic devices using the large-signal code TESLA-Z. The approach combines a precomputed complex impedance matrix for the structure Z with a TESLA computed admittance matrix Y of the beam-tunnel loaded with an electron beam. The gain matrix G for a given device then can be found as the product of the Z-matrix of the structure and admittance matrix Y of the beam-tunnel. Subsequent analysis of the eigenvalues of the gain-matrix G uses the Nyquist method to determine the stability of the device. We discuss details of the new algorithms and illustrate its application using available examples.