I used the output of the flyback circuit in my High Voltage Generator (set to around 15kV) as the AC input to a 6 stage voltage multiplier to increase the voltage to 90kV. I used two 20kV capacitors in series and two 20kV diodes in series for each stage of the multiplier to ensure I do not over-volt the circuit. I submerged the multiplier in oil to prevent arcs through the air.

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The (+) output of the voltage multiplier is set to the anode of the rectifier and the negative is set to the cathode. I supply ~13VAC from a variac to the filament to initiate thermionic emission. I did not have high-voltage resistors to properly load the output to the voltage multiplier to the tube, so I created a spark gap that closes the circuit to the tube only when the voltage is sufficient. This worked very nicely as a cheap alternative to a good high voltage supply. For imaging, I used cheap dental x-ray film. I am currently experimenting with phosphor screens for larger x-rays. I was able to produce viewable images at voltages of ~90kV and 20 seconds of exposure 1 cm away from the tube. Lead shielding was not required due to the very low energy x-rays being produced (dosage was ~15uSv where I was standing after several minutes of operation).