A cage for an insect (new grid)
Posted: Tue Jun 11, 2019 4:26 pm
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:
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: