Whole system microwaves

Tales of woe that teach. We learn best through failure sometimes
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This is for tales of woe that teach. We often learn quickest through failure that shows us how our thinking was off, and of course, sometimes it's funny at least in hindsight. Share your "Doh!" moments here.

Whole system microwaves

Postby Doug Coulter » Thu Sep 27, 2012 2:46 pm

Well, since our microwave ECR ion source worked so well, despite the difficulty of getting the ions out, I thought I'd try just flooding the system as a whole with 2.45 ghz, using more or less the same setup (haven't tried adding magnets yet for ECR).

I used the magnetron to coax adapter I recently described under the RF subforum, and essentially remoted a 1/4 wave antenna over ground plane into the tank. I had about 200w max power available of which perhaps 10 watts was lost in the coax and adapter, CW.

Nothing. Or almost nothing. Even at any pressure (I tried pressures more favorable to Paschen's law as well as fusor operating pressures), no lit up gas in there. Turning on the RF made the main DC supply draw about 2% more current through the grid, so it helped make a few more ions (or helped keep more of them from becoming neutrals again, dunno).

So, it almost worked. Time to try again. I can use the maggie in normal oven mode for 800w (4-5 times what I can get in CW) if I can find some coax that won't melt, or make some hardline. I can try adding the ECR magnets to see if that does any good, but none of the hoped for benefits have shown themselves so far - it's a null outcome at this point.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Doug Coulter
 
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