A cage for an insect (new grid)

[Doug Coulter]

For whatever reason, I found myself making a new grid...I can rationalize after the fact that we roughly quadrupled our Q and output going from 1.2" to .75" and going smaller might be smart. Or that the ion grid, while we haven't measured quantitatively, seems to have higher Q than the main grid - the big difference being it's a little smaller and out in the big tank (not even in the middle).

I'm a little conflicted about breaking vacuum to put this in - this tank has been continuously pumped down for several years and it's pretty clean in there.

But what the heck - I'l get this in there along with some other interesting things soon enough. Just seeing if I could feasibly make it at all was a step.

This one's a little under .5 OD, and 6 rods, which required me to make a new jig to hold end pieces for drilling (I cut off some extra and modified the old one I'd done for the big size) - and for getting 6 equispaced rods, since you can't get that with my cute little stepper motor arrangement that has 1.8 deg/step and no faith in micro stepping for this. So, a nice bit of hex stock turned down at one end to have a round shaft like the stepper, a vice, a lath chuck and the toolpost grinder-drill and here we are. I turned the stock down from .75" graphite vs buying more. Those drills hurt the wallet badly enough! I suppose I should do a workup on the fab for this, it's um, not trivial...

This is all either graphite or tungsten, fits tightly, tapped 10-32 which is what matches my feed-throughs and should withstand great heat without melting the end of the feedthrough if I use a not very thermally conductive screw to hold it. The materials themselves should easily go to white heat in a vacuum. We've run grids orange for long periods without melting copper or aluminum rods they were mounted to...and I don't plan to run this any hotter - there's been no real advantage so far to doing that anyway in terms of either output or Q - so far.

Looks like this:

with some of the broken first tries...this isn't real easy.

[Bob Reite]

I bought lots of extra small drill bits for doing my grid, knowing that I would break some.

[Doug Coulter]

I accidentally bought a couple extra...forgot what was in a drawer across the shop. With those .020 rods, it's really hard to find say, a 19 mil drill, and 17.7 mill is too small for a push fit. .020 drill, which is what I have, is too loose. So the trick was to drill all the holes in the ends tilted inward a couple degrees, so side tension keeps the thing together. I really do mean to do a workup of how I make these - even have a new camera on the way...I'll never be ToT or Click or Joe, but...I get it done. This is pretty close to the limit of what this human can do by hand, though.

I built a nice drill to mount in my lathe toolpost, use it also for cutting glass and grinding. I recently put in *really good* bearings, but frankly even the cheap ones were fine. Made my own collet for the end, and balanced it. If it has a mil of shake I can't tell - it seems perfect. Again,,,I need to document that better, it's kiey to the way I do this. The old dremel drill press doesn't really cut it and yeah, breaks drills. Not to mention lack of accurate depth control. Now I don't break drills, but when I make the graphite too feathery, or the holes too small and too near the edges, I break that sometimes.