Fusor Forums

I have a great naturally supplied screen in the throat of the turbo which is no where near the fusor. Look at my images! The fusor's vacuum port looks into the gravitationally down, flat metal valve face. From there it takes a right angle to an 18" long "S" bend of SS flex hose cable into the CF to KF adapter into the screen in the throat of the turbo.

Richard Hull

Dennis
The mode of destruction is not through the throat of the turbo. The major cause of failure is the use of coax high voltage leads that increase the capacity on the output high voltage this then causes higher dI/dt events causing ground bounce. yes star grounding in evidence much as possible. Not only is it dI/dt but dV/dt as well ie wires radiating into control wires. Even target current electrometers Kiethley were not immune I have a boxfull of dead front end ones that will get repaired one day.
so protection of sensitive inputs used those expensive metal cased diodes for electrometer inputs "PAD" something from memory. then all inputs protected with TVS diodes including turbo phase outputs. All High voltage coaxes RG213) protected with clipon ferrites (3) at each end this slows the dI/DT and dV/dt artifacts when an arc occurs.
Other stuff closer to the ion source potential also protected with strings of GDT tubes (Gas discharge tubes).
All wiring run parallel ie earth return and coaxes all together to limit current loop area. same again for control cables physically seperated from the high voltage but again with their own earth returns

Alas, the week before last was devoted to a probing in the dark at the turbo controller electronic issues. Had the controller been made in a 3R, 19" rack structure, it would be much easier to probe around in, electronically. I guess I poured in about 7-10 hours and just gave up. Last week, I didn't even go into the lab except to shoot my 22 target rifle with the "Silent 22" cartridges just released by CCI.

I went back out yesterday to disconnect the turbo and run the system with just the mechanical pump. #@$(*%^. The arc also took out the LED readout to the Baratron gauge. So I spent the rest of the day replacing its display assembly, de-soldering about 25 connection and then re-soldering after mechanically adapting the new display block to the old case.

More hassles....I remember the old bumper stickers on cars here in Virginia during the Kennedy administration. They said, "Gee, I wish Ike was back....Hell, I wish Harry was back!" To this I now add "Gee, I wish fusor IV was back.....Hell, I wish fusor III was back." At least fusor III did 200K n/s!

The beat (up) goes on.

Richard Hull

So very sorry to hear how extensive the damage was and possibly via cross talk along grounding wires?!

While I have used seperate grounds (differnt wall outlet circuits rather than a star) for my fusor vs. my detectors, never supected that a star system could kill a turbo controller.

When I get the new facility built (may just order a pre-cut building for assembly by me ...ugh, still a lot of work), I will be extra careful to use a seperate ground wire for electronics and another for the fusor (I have a water well I use as a master ground for the house but I can sepeate this and my house power company supplied ground. The well would be very useful for a low noise ground, anway.)

Again, I am extremely sorry to hear this and thanks for these posts - this will certainly help others prevent similar issues.

I never had a single arc in any fusor I have ever built!! Arcs do this routinely. I got away with 6 or 7 OK in fusor 5, but there is always that straw that breaks the camel's back.

Richard Hull

A single last look at this failed effort in images just before I rip it to pieces. I will start a new thread once I begin on the "real" fusor V. Hopefully, soon, as I gotta' have something fusing in October.


Richard Hull

Short, straight line vacuum lines are notorious for carrying HV plasma to critical components. Early on, two of my thermocouple gauge tubes were fried due to HV making it to them. Everything was well grounded but it still took them out. Now I have a series of bends and some distance between the chamber and the electronics.

Some people have zero problem with this as I have observed some fusers with the gauge right on the chamber and others struggle. No idea what is different but beware the traveling HV plasma as it will destroy your electronics with or without an arc. Of course the arc can momentarily jump voltages another order of magnitude or two so that just aggravates an already potentially bad situation.

Weak grounds can also suffer "ground bounce". Not nice either. Delicate FET based components, (everywhere now), are especially vulnerable.

Richard Hull

This posting thread is now officially closed as I have ripped the entire construct of the post down and will start a new thread as I struggle with the new fusor V that will hopefully never blow out the turbo or arc internally in any fashion.

Richard Hull