Thursday, December 29, 2011

Step 1 of {mumble} complete!

As you can hopefully see from the no-doubt indistinct phone-cam shot accompanying this post, the reconfiguration of the trigger electrode is complete.
reworked trigger plane web.jpg

Next step is to add the extra holes to the switch end-caps that I mentioned in my previous post. To do that, I need to be able to mount the lathe mount I made for the switch end caps into the mill vise. And to do that, I need a big pair of vee blocks than the pair I have. Right then, one more item added to the shopping list. Oi. Been meaning to get a pair for a very long time. I scored a small precision pair on eBay some time ago, but they are too small for this job.

After the mods to the switch are complete, I have to focus on getting the gas handling system and some kind of very fast trigger ready.

For the gas handling part, I have an air drier the media of which needs drying out, a vacuum system which lacks a precision manometer, and so on - about 3/4 of what I need is ready to go or can be. My vacuum system is technically down, but I only need the roughing pump, there's an additional port for that.

As for triggering this thing in field distortion mode, I do not believe the EG&G TM-12 which I have on hand, or indeed any trigger source EG&G made -commercially- is fast enough (gasp! Yes, I said it, tho I'll be delighted to be proved wrong, it just wasn't their usual bailiwick) to multichannel this sucker without going trigatron on me. Trigatron operation means a spark develops between the adjacent electrode and the trigger electrode, and that spark provides the ionization which fires the gap. Some switches are designed to work that way. Unfortunately, in this switch it would probably result in very bad erosion of the trigger electrode, so it's an operating mode to be avoided. I also don't believe that the Pacific-Atlantic Vector Inversion Generator (trigger pulser) is in working condition, although I haven't nailed that status down with certainty yet. I have another miniature VIG in a trigger panel for a Pulsatron I scored from eBay, but I don't know yet whether I can get that unit working either. There are one or two other options, and of course there is always the Marx, except that I think its output might be too high. I know, right? There are worse problems to have. OTOH, it isn't built yet.

Odds are good that I'll try running the switch with just the TM-12 for a trigger, at least once, because I'm dying to run the thing at all. Hopefully running it at relatively low power levels will keep electrode erosion down. The first test shots will be done with a 100Ω load at 10kV, resulting in 1MW dissipated in the load resistor.

And one way or another, I have to get the Bridgeport some 3-ph power again because so many parts and features I need to make require a mill. I am looking at a rotary phase converter from American Rotary, most likely. I'm done mucking about with inverter VFDs, I think. And if any reader is wondering why one doesn't simply swap the motor for a single-phase version, there are various very good reasons which I have arrived at through my own homework and which I feel certain the reader will find far more convincing if she arrives at them himself.

I think I shall shop for a capacitance manometer (Baratron, MKS Instruments) and a simple display for same (Duniway's TeraNova displays are nice) on eBay. I'll need to be able to read the gas pressure in the switch accurately and repeatably. It will take time to find what I need for a price I'm willing to pay, so I'd best start searching now.

This work was supported by The Joss Research Institute, Laurel, MD, USA.

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