The practical approachs to repetion pulse ps

[3l]

Hi Folks:

If y'all wonder what I've been doing the past few weeks...busy busy.
It took about two years to get a power supply that could handle
repetative charging and high power discharge...without breaking the bank or blowing up.
The system that seems to work pretty well is the stair step approach to power that uses different voltages at each stage so that back EMF won't fry the works.
I started trying to do it all in one step but it failed miserably.
To get the kind of power I needed required some interesting parts for sure. Two years ago I went with ss power supplies
with a step up transformer....burn't to a crisp. Diode charging systems were not even practical....switched to mercury rectifiers. This was latter changed to an inductive charging system to block high speed pulses down the power line.
Next came the switching element...the fun really began then.
I started out with a Hydrogen Thyratron...but it couldn't cut the
di/dt requirements that are necessary for a really fast high power discharge. So in comes the trigatron. Noisy requires shielding and constant rebuild in continous duty.
Trigatron was too slow ... the over pressure multigap was used for two months. It too had fun little problems too. it jittered a bit
and could not be reliably triggered by the main cap voltage.
Enter Topmg= Triggered over pressure multigap. The first gap is wider than the rest of the gaps. It is triggered just like a trigatron. High speed + reliable pulse output.
I had a large solid state thyratron rated at 36kv and 350 amps.
I dismantled it and tested it's snubber circuit to destruction.
It is fairly well protected from all but the nastiest back surges.
I was surprised at it really.... All I needed to do was to was to put an inductor in front of the gizmo to get it to work as a cap charging system. The transformer is a small dental xray trani with a large block transmitter diode series array in front for rectification provides the 30 kv voltage. I like some safety in the voltage to the ss thyratron..to handle the actual discharge the triggered over pressure spark gap does the deed. I retard the dicharge pulse in a home made delay line so the scr on does not coincide with the discharge of the capacitor.

new *****
I forgot to include the new way to match the impedence of the
the fusor...a motor driven vacuum cap. It is in series with an 12 microhenry choke to prevent destruction. While the pulse is going on the vac cap reduces the capacitance of the fusor while the driving pulse is being fed to the fusor. This reduces any delay to the wave of ions by cap blocking. The choke blocks the pulse after 1 ns or so so the vac cap doesn't arc back.

Happy Fusoring!
Larry Leins
Fusor Tech