Noninvasive vacuum integrity tests on fast warm-up traveling-wave tubes

A method of tube vacuum monitoring that uses the tube´s existing internal electrodes as an ion gauge is discussed. This method has been refined using present-day instrumentation and has proved to be a precise, simple, and fast method of tube vacuum measurement. The method is noninvasive due to operation of the cathode at low temperature, which minimizes pumping or outgassing. Because of the low current levels to be measured, anode insulator leakage must be low, and the leads must be properly shielded to minimize charging effects. A description of the method, instrumentation used, limitations and data showing results over a period of 600 days are presented