This is an interesting concept and is fun to watch. The idea is to have a pendulum which is connected to a high voltage source, and 2 grounded targets on each side. The HV is attracted to the grounded targets until an arc connects between them, at which point the attraction is reduced allowing the pendulum to swing back in the other direction. This can repeat for any length of time assuming proper conditions.
For this setup I used my 5 stage C-W multiplier which was powered by my CCPS transformer. As shown in the pictures below, I was using the original transformer from my C-W power supply with the CCPS drive electronics, but was not running it series load resonant. This resulted in 2 IGBT failures as I approached full power. I later then resorted back to the larger CCPS transformer, using the SLR topology, which turned out to work very well. I should have done this from the start, but my initial testing didn't produce desirable results. I found out later that my CCPS transformer was set up for too much output voltage and not enough current. Also, I wanted a single HV output with a grounded return. The solution was to simply use 1 of the HV secondary windings, which yields a 200:8 winding ratio. The maximum output voltage is then around 8750VAC (12.3kV peak). This allows for up to 123kVDC output from the 5 stage multiplier, though most of the time I never run it much past 90kV (that is scary enough!).
The CW stack. Note the 2 50k 200W ballast resistors and the 1V:1kV voltage divider (PVC tube laying diagonally).
The pendulum setup, foil ball hangs from some magnet wire. Elbow ducts and foil are grounded.
Shorter exposures of the arc.
Longer (1 second) exposures of the arc.
VIDEO (4.9MB, .AVI file, right click "save as")