I need to build a Geiger counter power supply circuit that will provide a 400 V DC output out of one of those 6LR61 9 V batteries. I thought about using a 555 timer to produce a square wave, feed it into a 1:45 transformer and then filter out the output, but I have no idea about what frequency and how many primary and secondary windings to use, and whether it would work at all.
update:
OK, thanks everyone for your effort but I guess I'll just go with a 555 inverter circuit like this (sorry for the watermarks), with custom transformer and a filter on the output.