by Doug Coulter » Mon Jun 01, 2015 11:58 am
From what I see in my fusor with 50kv and 10's of milliamps in regards space-charge beam expansion due to repulsion, I'd think ripple wouldn't be the biggest deal - you're lucky to make a beam of that perveance at all that has anything like a "focus" at a mere 10kv, and good thing you only have to hit the target, which can be a decent size. This isn't electron microscopy, after all. I wouldn't think you need all those kilowatts anyway, since in a vacuum, things heat up pretty easily.
But I agree on the huge caps - they are indeed huge in the 100kv/50ma supply I built - and there's still plenty of ripple even with caps that store more energy than a .308 rifle shell - scary stuff indeed. In my case, I can tolerate some series impedance and sank some ballast resistors into the oil - because an arc across one of those takes it out of the circuit, and 100kv is snakey-flakey stuff. I wound up using maxwell caps, not because I needed the tiny series R and L, but because that's what happened to be on ebay that month - 100kv stuff isn't common! Imagine a few thousand joules dumped in nanoseconds, resulting in a lab full of burning hot oil mist! Not my lab, you don't.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.