5.3: A large signal model of Extended Interactions Klystrons
Extended Interaction Klystron (EIK) cavities consist of shorted (resonant) sections of a periodic or bi-periodic structure. The response of such cavities to currents induced by the passage of a bunched beam may be represented by an impedance matrix that relates the voltage in each section to the induced currents. We have implemented this representation in the CHRISTINE large signal code. Using a modal expansion for the cavity fields we have computed the impedance matrix for a simple ‘ladder’ circuit. Using this matrix in a CHRISTINE simulation, we have found good agreement for the AC current vs. axial location in a 3-cavity circuit, compared with results from the 3D particle-in-cell code MAGIC.