The input gap voltage of a klystron

Following the discovery that several large-signal klystron programs did not agree on the value of the RF voltage at the input gap of a klystron, the question was examined afresh. Available textbooks were found to make restrictive assumptions about matching and/or tuning of the input cavity, assumptions which are no longer acceptable. A formula was derived, in terms of cold test parameters and drive power, that correctly apportions the power between dissipation, reflection, and beam loading, thereby determining the RF gap voltage.