Fascinating, but there is something missing in the equation there. A 100kV source does not inherently produce X-rays. Simply put x-ray sources are just fancy bremsstrahlung radiation generators that work by *abruptly* slowing or stopping accelerated electrons. Without a metal strike plate (anode) for the electrons to be abruptly stopped/slowed by there is no bremsstrahlung radiation. Likewise if there is gas between the cathode (electron source) and the anode there will be ion production and no electrons will reach the anode. Again, no x-ray production.
This is why Tesla Coils do not produce x-rays (unless cavitation of the air occurs right at a metal surface).
If they enclosed this piezoelectric HV source in a vacuum chamber and added an anode it would indeed be an x-ray source. But as it stands in the photo it is just a simple HV source, nothing more.