RF 'echoes'

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Doug Coulter
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Re: RF 'echoes'

Post by Doug Coulter »

You will be happy to know that the uWave source does indeed handle crazy-fast gas flows fine. It's just loafing at normal flow rates and pressures. I started with mid range rates, and have been going down from there ever since, and getting better results as I do. Some of the byproducts are best kept in the tank, it seems. I don't think gas flow in general is a big limit with any of the ion sources I've yet seen, anyway. Some I've tried wouldn't go low enough for me, this one will, and also too fast, just turn the knob for instant response, very nice indeed.

And it's not like D is real cheap to just blow through the system fast or that the approach is "efficient" by any definition at all. I'd concentrate on keeping them from recombining instead, if possible, and keep purity high via good vacuum technique, which is only a one time cost, not a flow rate. if you look at some ion traps, or even a quadrapole mass spectrometer, they can keep ions happy for long periods without losing them. So it's possible in practice at least under some conditions.

I would very much deny that most fusors don't need or couldn't be improved by an ion source -- just give both ways an honest try and you'll know that too. Here that's not what I see experimentally at all, even running the "conventional" modes. At the point a fusor is its own best ion source, the gas pressure is often too high, the current rises without apparent limit (some of this perhaps due to a lot of wasted tank volume in my setup that provides a lot of surface for recombinations and a lot of spare gas to reionize over and over), and the Q is terrible compared to other parameters I run much more successfully with here, all the time. I can reproduce all the results reported here by others on this system though, and have already as my baseline for improvements. It's just a scramble to reduce the gas after the thing lights off to a point where even a 2kw supply can get the volts up high enough for fusion again, without letting it go out and having to start over.

My point was simply, why go after better efficiency in the *lowest* power draw part of the system before you even get anything working? Doesn't make sense to me as an engineer or as a scientist.

It's too soon in the scientific process to deliberately limit your ability to search the multidimensional parameter space by limiting this and that too much in a misguided search for 50% better efficiency when many more orders of magnitude are what's needed to get to gain. All that stuff is simple (re)engineering once you have nailed down what you really need. For now, you can't say you know that. No one can. Got net gain, anybody? I don't see any raised hands, yet. No one is within a factor of magnitudes you can count on a hand even.

Believe it or not, btw, the hot rod is actually far more controllable, due to vastly better traction and an anti-everything-bad computer it contains (among other things like very nice tires and suspension), which neither my truck or Buick do -- I got some pleasant surprises in the recent ice storms here when I went out and deliberately tested that. I just keep it in first.

I do walk or take the Buick or kart when it's nasty as there is also a cliff to fall over and replacement cost for the old Buick is a lot less if the worst happens. Where I live, btw, no one walks to church, or nearly so (in my one case, it's practically in my front yard). Too far, all our land holdings dictate that one - we're all way too far apart for walking there in farm country, particularly the old and frail.

This ion source is also very controllable. Due to magnetic field line curvature outside it from the ECR magnets, you can have ion rates of very near zero if the extraction field isn't strong enough to pull the particles past that. It is extremely controllable even though it's also powerful. True, it's not efficient if you only want 100ua of ions (eg camaro at idle). I don't yet care about that, and neither should you.
And BTW, I'm off the grid and on solar or gas generator power, so in general, I DO care about what power things need to run. Compared to all the other things, this just isn't on the radar as yet.

I too think while in my armchair that pure monatomic ions would be best, it makes sense. Get rid of all electrons, and many (but not all) of the loss mechanisms go with them. for example, and those who think they don't have to deal with space charge regardless are very provably in utter error with the results I now have here. And the old math that also backs that statement up.

However, this new mode I'm running in with super high Q compared to all else here, about ~300x, there's only enough ions at the start to get a pulse triggered, rest are neutrals (most of them, in other words) and at gas pressures so low a fusor won't quite trigger itself without an ion source. So much for even trained intuition with a ton of real experience behind it (eg mine) -- the armchair fails again as a source of progress -- hindsight and standard model backed up by real experiment wins again.

Hopefully, it feeds the armchair part of me and now I make better predictions, and we wash, rinse, repeat. In some active drive mode with pure ions, yes, that may be better-- hope so, there's a lotta orders of magnitude left to go, so more better is needed. But I found the mode without that. In fact, with nearly pure ions, I can't get this pulse mode that has the high Q so far at all, but I'm getting up to active pulse drives rather than ballasted DC to continue to try that, as my armchair does think that will be best in the end.

I do now have a theory of all this that's passed the Feynman test a few times, so I will share that on the appropriate thread soon - I am in running fusion and gathering data to back it up further mode just now.

Easier to resist the firestorm of flames I know I'll get from the skeptics when I am utterly sure I'm right (already, 20 runs replicated with changes matching predicted results thereof) and can by golly prove it in any way I'm asked to, which is almost "right now". Just a little more data collection to go at this point.
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Linda Haile
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Re: RF 'echoes'

Post by Linda Haile »

So SWR or echoes is not something we need to consider at this stage? I'll start another thread soon on inductively coupled plasma. I'm considering a transistor driven HF tank circuit rather than a magnetron to start with. I've achieved CCP before using a similar circuit with argon at STP, so I think I have a starting point now, especially if I don't need to worry about SWR.
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Doug Coulter
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Re: RF 'echoes'

Post by Doug Coulter »

Not with a magnetron, no, no worries. With solid state, yes, definately! SS ability to handle any peaks of any sort is insanely terrible compared to any tube thing. Much solid state homebrew class gear will go up in smoke in a second or two with SWR at 2::1, so you'd need to test and match at lower power, or provide a lot more available power in the SS system than you need so you can still light it off at something under half power -- opps, that's not efficient! Sometimes what is best isn't as obvious as you'd think.

Though why you'd use an expensive SS thing compared to a free dumpster magnetron I haven't a clue unless you're running it on batteries or something up on the HV terminal. From reports I've seen, though it doesn't make a heck of a lot of sense, people are using much higher powers at the lower frequencies (13.59 mhz) than at the Ghz, maybe it takes more there, but it's not obvious to me why that would be. I chose the 2.5 ghz as that makes the magnetic field for ECR (which is a huge improvement in efficiency and running range of gas pressure) a decent number -- not too big to make easily, and not so small that fields in the lab would affect it. When you get down to the few gauss range, that becomes a problem itself. ANd if you're not doing ECR, you're not caring about efficiency -- that's a factor of about 3-5 better with than without in testing here, not to mention running a lot bigger range of gas pressures with no other changes, which is merely handy. With the magnets on my thing it will stay lit to below e-6 mbar, which is kind of nice sometimes.
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Linda Haile
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Re: RF 'echoes'

Post by Linda Haile »

Very interesting, Doug. You ask why transistors? I wouldn't say I'm out to re-invent the wheel, Maybe the wheelwright's apprentice, though. I want to start from first principles, or at least with what I already know, and work up from there. I'm doing this to learn about ICP from the experimental viewpoint.
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Doug Coulter
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Re: RF 'echoes'

Post by Doug Coulter »

In that case, you should look into some of the designs the hams are using for solid state linear amps, many are fairly extra rugged and moderately cheap as well. Now, a linear amp won't be very efficient (about 50% if lucky) but it would be a good thing to have in the lab anyway, and those only take a couple watts to drive. Many of the ones I've seen run fine on 12 volt dc, making it possible to do battery operation should you need to go off ground as well. Then get some ideas from the design (many are written up in detail in ham publications) and make your own if you like. You'll find the reasons this or that pcb track gets wide here and narrow there for close control over capacity to ground at some point and a lot of other cool and necessary tweaks that make them rugged and broadband. Many will cover the range of interest here.
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Linda Haile
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Re: RF 'echoes'

Post by Linda Haile »

Thanks for the advice Doug. I plan to do some experimenting soon starting with my CCP circuit but modified for ICP. As I blow things up I'll modify it with an aim to increase frequency. I'll be using argon to start with as it seems easy to ionize and it is cheap.You can't beat hands on experimentation for learning rather than just copying another design. I find your posts and Chris Bradley's quite interesting but I'm not sure where Chris's experiment is going.
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Doug Coulter
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Re: RF 'echoes'

Post by Doug Coulter »

You are most welcome, thanks for putting up with my sometimes excess verbiage.
Hard to beat hands on, and yes, I use argon too. I found N2 does some interesting but mainly nasty extra strange effect things -- I will be putting up some movies about weird sudden ion recombinations/large N polymer decompositions soon on you tube. Till then, Ar or He are good, as Ne is expensive. Though, I must say, really impressive in an ionizer, blinding bright when you get it right.
You could also fool with H2 from electrolyzed water, ala Seltzman's thing. But be careful with that so an accident doesn't pull water into your system.

I do know where Chris is headed, but I don't know if I'm supposed to tell. His theory is fantastic and a real breakthrough, but it seems he got caught up some in some pretty glows short of pushing to make it real according to plan. I think this is fine, as everyone does that at some point before moving on the the real deal Basically, he's trying to make a novel cyclotron, wherein more than one set of beam going roundy round in the same H field "rub" at the edges, and has a way to re-focus with low energy loss those particles that don't fuse but do scatter, as well as handling the monkey-motion along the H field axis, the idea is pretty slick, actually (and patent pending IIRC). Now if we can just get him to start running real conditions and trying to make his idea into actual reality.....My analysis (under NDA) shows it will actually make fusion practical, or a heck of a lot closer than we are now (even including my recent 300x improvements). Could be good, stay tuned. If I could talk him across the pond to use my lab etc, I would.
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Linda Haile
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Re: RF 'echoes'

Post by Linda Haile »

Maybe he has limited resources, but I think we're going off topic here, although this thread has served it's purpose as far as I'm concerned.
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Re: RF 'echoes'

Post by John Futter »

Lyn

Please drop the term echos it grates the nerves to an Rf professional
The correct term is return loss or mismatch loss. A slang of this used commonly by amatuer radio enthusiates is SWR. shortened from VSWR or Voltage Standing Wave Ratio.

My companies website has a little discussion on why bipolar and mosfet RF amps are susceptable to imperfect loads and getting more power to the load by using attenuators (Iknow this sounds counbterintuative)
This probably is the best way for you to use a solid stae PA to drive your ICP or CCP without damaging your PA. Using an SWR meter between the attenuator and your ICP load will then allow you to tune without damaging the PA or have it rapidly turn down the power

Link
http://www.iel-rf.com/AttenuatorsDescription.html
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VSWR...return loss.....mismatch loss....

Post by Linda Haile »

John, Thankyou for your input, I appreciate it. 'echoes' is a term I came accross while researching RF sources. Doug explained that this is the same as SWR, which I have come accross before. I also came across the term 'auto-match unit', as used in commercial plasma sources. I agree that I should have dropped the term 'echoes' earlier in this thread because, as you point out, it is a slang term. Thanks for the link, I will explore it in greater depth in the near future. I'm still learning the nuances of RF sources and any useful pointers are most appreciated. I believe I now have a rudimentary understanding of what was meant by the term. I admit I do find VSWR a lot easier to comprehend than 'echoes'.
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Re: RF 'echoes'

Post by Dustinit »

To get a better handle on the reflected power due to mismatch
I found this program that may help and interactively explains it beautifully.
It can be found here

http://www2.fh-rosenheim.de/diegelmann/ ... nglish.htm
Look for the title
Reflection and Transmission at an Impedance Mismatch.

At the bottom z1 is source impedance z2 is load.
green line is voltage into load or termination
red is source voltage blue is reflected
black is the sum of source and reflected and is what is seen at the source.
echo terminology grates because the wave is continuous but would be relevant
for pulses shorter than the transmission line length.
Hope this helps .
Dustin
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Doug Coulter
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Re: RF 'echoes'

Post by Doug Coulter »

Guys, I know some of you are "RF pros" for sure, as am I. I am also expert in fields where the term echos is more appropriate as well, when for example digital switching is involved where lines are a fraction of a wavelength for some frequency components, and many waves long for others. This term is used in the ISO PCI bus spec and many other places in digital land, as it makes way more sense than return loss or SWR there. Lyn wasn't all wrong to use it.

SWR and return loss are fine for narrow band, steady state where the results of a lot of cycles are added and smoothed out into the nice peaks and nodes. Now handle the case of a single step function that way -- echo makes *far* more sense in that context, not to be all that pedantic about it.

Obviously, it's the same root phenomenon either way, but one way talks far more intuitively about single events, the other for narrowband steady state situations. Step outside your narrow specialty! There are no "standing" waves in a single step or impulse event, it all flies back and forth on the transmission lines precisely as an acoustic echo goes back and forth between reflecting walls, so it makes sense to think of that way, and the RF concepts don't work as well for that at all.

Jargon and overspecialization, don't get me started! Both obfuscate and make things harder to understand when getting a little outside the box. And this forum is about just that --
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Re: RF 'echoes'

Post by John Futter »

Doug
Iwas under the impression that lyn was going to drive his ICP/ CCP with CW RF not pulses.
I agree Echo is acceptable for pulse work whether it is RF, audio, electronic but not for CW
Try a web search for eliminating RF echos and it will not give the info Lyn wants --unless he is really trying to build an NMR which in this case is using pulsed RF.

Use the correct terms and then searching will provide the appropriate answers
From memory I think Lyn has a solid state ENr RF amp around the kilowatt level his ICP should only require 20 -80 watts so a 6 to 10 dB attenuator should keep the amp more than happy ie a return loss of 12 -20 dB presented to the amp output.
A cheap wideband attenuator is a 100m roll of RG58 5dB attenuation @11MHz, 10dB attenuation @ 22MHz etc. At this power level I would keep the roll of cable in a bucket of water for extended runs.
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Doug Coulter
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Re: RF 'echoes'

Post by Doug Coulter »

Oh agreed. I was just saying the term isn't categorically in error. Even standing waves don't stand, it's just a superposition of echoes, well explained in say, the ECL handbook.
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Re: RF 'echoes'

Post by Linda Haile »

John, I don't have an amp at present, maybe you have mistaken me for someone else. I'm planning to try different circuits including some built from scratch starting in the 20-80 watt range as you suggest. I'm starting from the pretext that an ICP source is a transformer with the plasma as the secondary as I believe this description is the simplest definition of an ICP source. My previous experience in this field is with air core transformers in Tesla tank circuits and I'm planning to build on this experience to develop an ICP source from first principles. I'm planning to experiment with tank circuits, linear amps and ferrites initially, rather than magnetrons. I've no idea which of these approaches will work (or work best), hence the experimental approach.
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Re: RF 'echoes'

Post by Carl Willis »

Steve Robinson is the fellow with the big ENI amp.
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