Parametric capacitor made of two plates
Could it be the capacitor self-oscillations? This question can help to answer the following experiment, which involves two plates between which is a dielectric, and to which is supplied a sine wave generator. Self-oscillations of such a system removed the coil connected to the oscilloscope. One plate is a copper sheet, the second ferromagnetic. The plate is sandwiched between permanent magnets. As the dielectric uses a special polymer film.
In the following video we can observe self-oscillations of such a capacitor, which is not similar to a sine wave. And strong the scan we can see on the peaks of some of them — a small NMR.
In the next experiment, one plate is connected to the output of high voltage multiplier and ground. Of the following video we can observe a relatively large electric potential on this capacitor, and its discharge is disabled when the voltage source. The author managed to achieve on a single charge of about 100 digits!