Diode oscillation in high-voltage klystrons

Diode oscillations at frequencies between 1350 and 3700 Mc sometimes occurred in a particular high-voltage pulsed klystron. These frequencies agree closely with those calculated for an inverted spherical diode. The oscillations are often delayed a few microseconds after the electron beam is turned on. Experimental techniques revealed that two of the modes, TE41and TE61, with Q's of about 1000 had their highest electric fields in a region of the electron gun remote from the beam.