Laser-Optical and X-Ray Characterization of an Operating High-Voltage Piezoelectric Transformer in Multiple Vibrational Modes

A crystal of lithium niobate was configured for use as a longitudinal-mode piezoelectric transformer (PT). An electron gun was coupled to the transformer to allow for controlled release of charge to the high-voltage terminal of the PT. An electron tube extracted a beam from a thermionic emission source, and cylindrical optics focused the beam to a 2-mm spot at the PT output. Two diagnostic methods were used to measure the operation of the PT: bremsstrahlung X-ray spectroscopy and laser-optical interrogation. Both diagnostics showed that the PT is able to process up to 1.5 $\mu \text{A}$ of current at 20-kV output in a continuous mode. The laser-optical method was also used to compare the mechanical stress, electric field, and developed voltage between the fundamental and secondary harmonic resonance modes.