I need capacitors rated for 50 kV. Buying them is an option but the ones with appropriate voltage rating I have seen cost more than 50€ which is far too much.
That's why I want to make caps on my own but the simple aluminium foil - plastic foil - aluminium foil trick won't do it. Such caps can barely resist voltages higher than 5 kV. I plan to stick to aluminium (good idea?) for the plates but I need a much stronger dielectric.
I have heard about several materials to use as a dielectric for voltages that high:
- Distilled water: It has a breakdown voltage of 65 to 70 MV/m (Wikipedia). The problem is the forming of ions within microseconds after applying the voltage which lead to an immediate breakdown. This can be prevented by keeping the water flowing and deionizing it somehow. Thats rather complicated though as I would need a pump, a filter and a water circuit.
- Waxed paper: It has a breakdown voltage of 40 to 60 MV/m (Wikipedia). Waxed paper is, as far as I know, basically the same as baking paper. It would be a lot easier to use than water but it comes in thicknesses of about 0.1 mm. Assuming a dielectric strength of 40 MV/m (=40 000 V/mm) it would need to be at least 1 mm thick. I don't think that folding it/putting several sheets on top of each other does the trick.
Do you have an idea on how to achieve my goal? Wikipedia lists a lot of chemical substances with crycptic names that have a high dielectric strength. Maybe one of those is easy to get/produce an can be used by an amateur like me? Hopefully someone is more experienced in this topic than I am.
I need the capacitors for a Marx Generator powered by a flyback transformer which supplies approximately 50kV. Capacitance isn't too important but the higher the better.