Science/Engineering/Technical forums

A Few pics of what I'm doing the last few days
The dual implanter is in bits getting new Quadropoles an steerers. The big magnet in the pic is going to rotate so that the ion source end is pointing straight up, where it will get a 200kV terminal put on top of an acceleration tube.
Other pics self explanatory

Yup, definitely creates the drool reaction!

I would love to see some pix of how the real HV is handled, since I'm getting ready to move up to the hundreds kV range here too, and don't really have a good clue how to handle that well. 50-60 kV was pretty challenging to get reliable. Of course, most of the problems were really on the tank inside, with hot deuterium hitting the insulators and wrecking them, but still...
At 60 or so, troubles start to happen on the air side too, with streamers etc.

The inputs to the steerer look like spark plugs!

Doug
I will post more pics of the HV setup soon
and yes all those feedthroughs are sparkplugs the cheapest Vacuum high voltage feedthrough available

I'll be looking forward to that -- my HV supply is coming along nicely. With just a little tuning, it's drawing about 60ma off the fet rails, at 35v input (out of possible 160v). No load of course, but it makes nice arcs and nothing gets unhappy. So at this point, it's mailny getting it all packaged up.

We've tried various sparkplugs here, best so far was some hard to find ones from an old model Ford (A or T, not sure). The ones with R in them burn up too easy, and we've had some that leaked.
The ones I see in your picture look better than any we've used yet -- long on both ends, so easy to work with. Any numbers on those? Here, you can't just to in the auto parts store and look around to find things like that (the old time mom and pop stores are all gone) -- you have to know a number (or a car that uses them). Ones without an R are getting hard to find at all.

R plugs have a resistor in them to help eliminate radio interference.

Go to a small engine shop. Small engines almost never use resistor spark plugs.

I did that, and believe it or not, found some that are a standard 3/8" thread, making that part easy. Most small engines here now also have R's. And those leaked around the ceramic/metal seal (fixed with epoxy) and were so dinky as to be hard to work with, and then the R burned out with 10 ma dc on it in only a few minutes -- I was running an older design ion source with it.

It's probably different in NZ but here, it's all getting so politically/environmentally correct it's dumb, and the good old stuff is getting to be hard to find. Seems the plugs you are using are longer on both ends -- making the inside side a lot easier to weld something onto and insulate the mess from the nearby ground than what I've been finding. I have seen people put them in the other way -- in some conditions (like fusor gas pressures) you need more insulation length on the inside than the outside!

Guys
these plugs have no resistor NGK D7EA

We buy them new in boxes of 10 1 in ten fails the Helium leak test. we have a threaded for sparkplug NW25 blank that fits straight on the leak tester.

Thanks John, sounds like a plan! With a number I can special-order things that the usual chain store doesn't stock. A good idea to leak test them in a jig first, too. I found mine on the main system, since that's where the mass spec lives (and it has a He leak-detect function). All kinds of uses for those, not main HV obviously, but there's plenty of other things one does in vacuum that could use them at a large cost savings. I was especially looking at how long the protrusion of the inner conductor was into the vacuum side. There's a lot of "flat" plugs around that make it hard to get a connection there with a bit of insulation around it -- this one looks easy. I already use plug wire a lot around here. Only one bad thing about the Accel racing stuff I use -- it has a high dielectric constant, so unless you stuff it into grounded braid (as from RG-8) it gets a big charge on the outside and makes dust fly around the lab -- and even charges up proximate humans, who of course find out next time they get near a ground. OW!

Doug, Hi. I think those big plugs we used were from a '40 Ford Flathead. I think I got the number from Andrew Seltzman's website. 1/2" NPT I believe. -bill

Yeah, those are pretty darn good, not as long outside as you'd like and yes, plain old 1/2" npt, meaning it's easy to find a good tap for and they seal well to the gear. Now if I can just find the other 3 you got us....At least there was a lotta room around the center conductor, making it easy to weld on an extension and then slide a ceramic tube over the whole thing -- going back down into the plug cavity until it became a tight fit on the taper of the plug's insulator. IIRC the one we put on your rig never failed in any way. The number John just gave us looks worth looking into as well -- much longer stalks on both ends. Looked like he had enough center conductor on those to just clamp something to -- very cool. And duh, why didn't we think of using ignition wire and boots on the air side? Seems John's got it goin on.