Reentrant klystron cavity as an electromechanical transducer

The resonance properties of reentrant cavities with circularly cylindrical and conical inserts are examined to quantify the resonant frequency dependence on the gap spacing between the end of the insert and the cavity´s top plate. An experiment performed on a 1.0 GHz cavity fabricated from aluminum shows that the resonant frequency downshifts when the top plate made 1.0 mm thick is loaded at the center with weights as light as 10 g. This translates into a tuning coefficient of 3.0 MHz/μm, which can achieve a three fold increase through optimization of the cavity dimensions looking at application of the transducer in gravitational wave antennas.