Rsh/Q0 measurements in klystron cavities

Abstract

This paper presents the experimental results of Rsh/Q0 measurements in klystron cavities using the perturbation technique. The theory involving this technique results in an expression which depends on the natural frequency f0 and the perturbed frequency shift Δf, both measured using a cylindrical reentrant cavity with offset gap built in the laboratory. In addition, it is used a cylindrical cavity (pill-box) to calculate a constant that depends on the geometry of the perturbed object, as well as analytical expressions to calculate an integral factor that relates the square of the voltage on axis and the electric energy originally stored in the small volume of the perturbed object. The values measured of f0, Δf and Rsh/Q0 are, respectively, 2.86 GHz, − 5.27 MHz and 79.8 Ω. They are also compared with the results simulated by a 3D eigensolver obtaining a good agreement.