Archived - EXP: A New Year's treat; Crimzon doughnuts.

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Chris Bradley
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Archived - EXP: A New Year's treat; Crimzon doughnuts.

Post by Chris Bradley » Sat Jan 02, 2010 1:22 pm

SUMMARY:

Type of Experiment: Penning-type fast-ion toroid, proof-of-principle trial.
Drive voltage: 1000V
Drive current: 14uA
Ion energy: Presumed possibly up to 1keV
Ion current: Inferred to be 1mA

Conditions: 0.15T. air background; controlled to 1 to 20 microns by a bleed valve to atm

Outcome: Imaging of a toroid lacking any apparent electron-recombination irradiance

Diagnostics: Only visual imaging, to date. Subjective analyses only.
Prognosis: Ongoing experimentation required, initially with various e-field regimes and further subjective visual interpretation.

Specifications:
magnetic head = 150mm x 150mm x 52mm, 6mm mild steel plate
working space = 40mm gap, max. 65mm operational radius, kapton tape for e-field modification
outer electrodes = 4 x [approx 80mm x 25mm], copper, mounted to bakelite supports and aperture moderated by teflon wrap
inner electrode = 4 x coupled 1mm SS rods
magnets = 4 corners x [3 pairs x (22mm diameter/20mm high 'discs', N42)] = 24 magnets, total, wrapped in 0.5mm teflon sheet.




______________________________________


I have been contemplating when might be a good time to feed in some initial work from my experiments and have concluded that the forum could do with a fresh injection of something new right now. Also, to me personally this new year and decade feels like it has promise of things to come and I would like to invite and incite you all to the same degree of excitement and expectation as I have!

So, I will introduce an outcome of my work and see what you think of it. (I especially dedicate it to Carl who has been hanging on so loyally to this forum, through some tortuous exchanges of late, just to see some new experiments.)

Now, please take on board that there is much I don't yet know about my own experiment. The work is ongoing. So whatever I might say about what I intended the experiment to do, what I think it does, &c., all of that might be wrong, and for now you will have to make up your own minds on what you're actually looking at. I will therefore be trying to say, and reply with, as little as possible so as not to bias your opinions of it.

The first picture shows the assembly that I have installed in my 'bakelite' chamber (as per viewtopic.php?f=15&t=7222#p49094 )

It is designed according to the principles of my assembly; viewtopic.php?f=15&t=7189#p49061

..but that there is now a central electrode and 4 outer electrodes, each with an independent connection. The actual design intent is to have transparent grid-like electrodes so that scattered ions might be recovered back into the working volume, which also means those permanent magnets wouldn't be there. So this is just 'demo' kit to explore proof-of-principle. The design intent is that the inner electrode and chassis are +ve and the outers are -ve so that, if you like, the intention is that there will be 4 'little fusors' within a magnetic field with planar cathodes but that the recirculating ions get caught in orbits in the magnetic field whilst they are inside the magnetic field.

To put it another way, it is a Penning trap with the end electrodes having been pulled into the central axis. And, whereas a Penning trap tends to accumulate ions at its centre, because I've stuck an electrode in the middle then they can't accumulate there and instead orbit further out.

Or... to put it a third way, it is an 'ion magnetron'.

The second picture shows a closer view inside the device between two of the magnet/electrode 'corners'. The reason I put that particular image in is because the last image may be difficult to orient yourself to, without having the day-light view to compare it with.

The second and third images are exactly the same view but that the third has 1000V applied and is drawing 14uA. That is a total indicated input of 14mW! (and of course, it is in the dark! The image was a 15s exposure and I still had to push it 3 stops [effectively a 2min exposure – my camera doesn't do more than 15s!]). Pressure was around 10 microns, but I wasn't watching that closely and I can't vouch for the accuracy of my gauge.

My interpretation is that there are no visual electron recombinations going on at all. The light is purely what is being generated by fast-ion stimulation of background neutrals, implying both that there *are* fast-ions and that they have a concentrated density in an orbital track where they are colliding with the backgrounds, as was the design intent.

Now you may say, “what's the good of 14uA! That won't get a fusor going!”. That would be to misunderstand that this isn't a discharge plasma, as in a normal fusor. The electrons are all but arrested in this magnetic field and so there is essentially no conduction, save for a small dribble of orbit-hopping electrons and scattered ions. (you might like to note another previous post of mine; viewtopic.php?f=6&t=2854#p12364)

Instead we can look to the physics of the Penning trap and note that the Brillouin limit would suggest a density limit for protons of 4e14/m^3 in a 0.15T field (which it has been measured as). In turn, the rotation frequency of 1keV protons [just an example species that might be in there] would be 1MHz which, presuming there to be 30cc's of torus there (because I have noted that the vertical extent of the torus is that of the electrodes, and I have restricted that to 1cm here, and that the radius is ~4cm) then the ion current might therefore be calculated as 1mA past any given point in the device.

You might still think that is still little, compared with what gets a fusor buzzing, but now consider that the ion current in a fusor is, at best (according to my analysis), 1/240 of the applied current due to the way the electrons run around in the fusor's discharge. (see my previous post; viewtopic.php?f=14&t=6831#p42514) So I would hazard a guess that, e.g., a 5mA fusor is pushing no more than 20uA of fast-ions around at any one time.

The comparison with a fusor, then, is that the image below may depict the input of a 14uA current for a 1mA ion current, whereas a fusor puts in a 5mA current for a 20uA current – a potential improvement of around 5 orders of magnitude if these interpretations bear up.

Now bear in mind that Brillouin teaches the confinement is proportional to B^2, so if someone were to build a x100 factor = 15T version of this device, (which seems plausible, given the small volumes possible) then presumably the improvement might be x100^2, or 9 orders of magnitude in total... ..fine promises, indeed!!

As mentioned above, I may not be particularly forthcoming on discussing this as I might usually be, until such time as I have progressed experiments, so please do make your speculations and don't expect me to know or be able to correct you, because they are probably nearly as good as mine!

Happy New Year!!!!....
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Kade
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Re: EXP: A New Year's treat; Crimzon doughnuts.

Post by Kade » Sat Jan 02, 2010 6:56 pm

Chris, great experiment, nice pictures.
I wonder if the apparent "volume" of the torus, may be due to the time exposure in combination with the radial instability of the ions as shown by the simulation by dave cooper ?
download_thread.php?site=fusor&bn=fusor ... 1219430899
Best Regards:
Kevin.

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Chris Bradley
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Re: EXP: A New Year's treat; Crimzon doughnuts.

Post by Chris Bradley » Sat Jan 02, 2010 7:30 pm

Absolutely possible! Though just to clarify, I have already re-built this experiment a few times and in the first instance, those electrodes are an inch high, and the torus was an inch thick. So I figured that the e-fields were directed in such a way that ions could, without stepping against any energy gradients, move anywhere within that height. So, naturally, I reduced the electrode width (all I did was roll teflon tape over top and bottom, which you can see) and the torus shrank accordingly.

Perhaps I might just replace it with a horizontal wire at some stage, though I suspect the e-field strength will begin to drop off so much that containment will be lost and nothing will be seen. But, yes, it suggests further possible experiments and ions would be free to execute epitrochoidal orbits. That's pretty much why I was thinking I might calling it an 'epitrokotron', if I was in need of a particular name for it.

Kade
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Re: EXP: A New Year's treat; Crimzon doughnuts.

Post by Kade » Sat Jan 02, 2010 8:23 pm

The Teflon tape result is interesting given that the static permittivity is about 2* the vaccum permittivity, and should not have eliminated the electric field, only the electron conductance in the insulated region, unless I have misunderstood what's going on (quite possible at this stage).
Regards:
Kevin

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Carl Willis
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Re: EXP: A New Year's treat; Crimzon doughnuts.

Post by Carl Willis » Sat Jan 02, 2010 8:37 pm

Hi Chris,

This is a cute piece of equipment, and yes, I'm pleased that there is physical substance here to talk about. I think "ion magnetron" adequately summarizes the operative idea. Thanks for the photos.

It looks like the central anode is comprised of four or maybe more parallel wires. What did you have in mind with that?

The discharge appears very red in the photo. Just looking at it by eye, does it appear this color? I would not expect that color from a gas discharge, but sometimes solids placed in an environment with a lot of particles and radiation produce these vivid colors by fluorescence. Just another thought.

As might be expected, I do take issue with your suggestions about trapped ion density, current, and energy in your device and the comparison with a fusor on some of the same quantities. I think all that is pretty much as close to totally made up as one can get, to the point of being worthless or misleading even for illustrative purposes. As you admit, even the first assumption--that the major species might be protons--is a big stretch. That they might be present in the magnetron at something close to the Brillouin limit is another big stretch. Then there's the 1-keV assertion. And so on about numbers for the fusor. I just don't see value in all the speculation.

Consider this experiment: If you are trapping protons in quantities like your supposed number, the stored charge in the trap is ballpark on the order of the capacitively-stored charge on the magnetron electrodes and the trap filling current will be noticeable (relative to the capacitance charging). Although crude, such an observation would probably be accessible to your budget and apparatus, and would be something concrete to hang your assumptions on. You'd know in one fell swoop that (A) the trap is actually trapping something, and (B) you'd have some bounds on how much charge is there. With some better experimental control, you could probably make the convincing argument that the background gas is mostly hydrogen and the trapped species mostly protons. There may be other creative and effective methods for getting a handle on ion density without going broke, but this is what popped up in my head. With amateur fusors we have gone on a long time without much of a handle on these numbers because they're hard to measure, and consequently there hasn't been much to say about them.

-Carl
Carl Willis
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TEL: +1-505-412-3277

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Chris Bradley
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Re: EXP: A New Year's treat; Crimzon doughnuts.

Post by Chris Bradley » Sat Jan 02, 2010 9:04 pm

Not sure I follow. It is non-conductive and therefore will 'hold' an electric field. The fact that it works (and appears to work very well, without complication), might suggest that there is only ever imbalanced local charge there (ions only?) and not a neutral plasma that can interact with it.

But.. as said, your guesses are good at this stage...

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Chris Bradley
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Re: EXP: A New Year's treat; Crimzon doughnuts.

Post by Chris Bradley » Sat Jan 02, 2010 9:36 pm

Carl Willis wrote:
> It looks like the central anode is comprised of four or maybe more parallel wires. What did you have in mind with that?
Yeah, don't worry about that in this particular experiment. I fitted this in the last cycle of testing in preparation for some further studies. Basically, one of my ideas is to form extra ions at the centre by appying a smaller differential potential across the different wires (they are each independently connected - but currently are tied together at the same potential). That way I might anticipate that ions formed at the centre can be accelerated to the full outer potential and are therefore likely to 'enter orbit' at 'full speed' to the applied potential. But that is not operating in this pic. All ions begin generated are being generated by the self-maintained ionisation of fast particles within it.

> The discharge appears very red in the photo. Just looking at it by eye, does it appear this color?
Yes. It looks almost exactly like this to the unaided eye. With a little more power being fed in, perhaps I might say slightly more 'orange', but it is a very low intensity colouration and I have no reason to tell you this isn't a true representation of the colour.

I tried to get a video of this yesterday, but the camera I've got just isn't sensitive enough. I get a 'usual' purply glow at, say, 0.1 microns then as I bleed gas in it changes to this deep red colour.

> I would not expect that color from a gas discharge
I do not consider it a gas discharge. I regard it as pure excitation of the backgrounds, and, thus, no 'purple' colouration from electron recombinations. Unlike a gas discharge, I would suggest you're looking at an image free of visible electron activity.


> As might be expected, I do take issue with your suggestions about trapped ion density, current, and energy in your device and the comparison with a fusor on some of the same quantities. I think all that is pretty much as close to totally made up as one can get, to the point of being worthless or misleading even for illustrative purposes. As you admit, even the first assumption--that the major species might be protons--is a big stretch.

Sorry, I mis-directed you there. I was merely trying to indicate the range of rotational speeds for the different species, protons being the most extreme.

What I would say is this; if you run through Bq=mw (or Bqr=mv, if you like) then the only things you find that would fit for B=0.15T, an r of around 4 to 5 cm, and E=1kV are particles of m/q=2. So my best suggestion at this time is 2H+, seeing as I am using only air as the background medium so at this pressure it'd be mostly water. What I can say is that it takes a short pause for it to form up, and if I made a presumption that it is doing a m/q selection, then it is hardly beyond the realms of possbility, given the setup.

> That they might be present in the magnetron at something close to the Brillouin limit is another big stretch.
If there was a focussing accumulation of ions at the given radius, then I would expect it to run up to the Brillouin limit, then self-limit itself. This is the design intent. Again, of course I cannot say this is so, but that's what the 'theory' is aiming to do.

This is exactly what I designed the thing to do, so I have no reason to 'self-doubt' what I've done just yet. If I designed it to accumulate ions in a toroidal focus... and it appears to do exactly that in an experimental trial... then I will keep an open mind that I just "got lucky" but I'm not going to presume in teh outset that my design intent is the least likely thing to happen!!! I'm now looking for indications that it *is not* working as I intended it to, and so far I have no reason to think other than it is working as designed.

> Then there's the 1-keV assertion.
It's driven by a 1kV potential. How fast do +1 ions get in a 1kV field? And what else would orbit at 4cm radius in a B=0.15T field?

> Consider this experiment: If you are trapping protons in quantities like your supposed number, the stored charge in the trap is ballpark on the order of the capacitively-stored charge on the magnetron electrodes and the trap filling current will be noticeable (relative to the capacitance charging).
Not sure how I would measure that. The issue is that it is not yet design intent and I would expect a continuous stream of losses into the electrode as they are solid and as there is not yet the design-intent recirculation (like 4 little fusors). When I power it off, the torus dies almost instantly, so the energy confinement time is too short to take any such measures just yet. Is there some other way of doing the measurement you envisage?

> Although crude, such an observation would probably be accessible to your budget and apparatus, and would be something concrete to hang your assumptions on.
For now, I am just exploring the e-field configurations to see if I can come up with an outcome so blindingly clear that further diagnostics would be merely a cursory exercise.

In return, I ask a simple question of you: How else do you explain the ring of emissions in a B=0.15T field, as you see here, if there isn't circular ion entrapment going on? What other explanations fit the photo? If it's easy to say there may be other explanations, other than mine (and for which this specific design was created to perform), then I guess it'd be easy for you to say what they are? And they are...?

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Re: EXP: A New Year's treat; Crimzon doughnuts.

Post by Kade » Sat Jan 02, 2010 9:40 pm

OK, got it now I think!.
The surface of the Teflon exposed to the ions, will take on a positive charge effectively becoming another anode region.
- Kevin

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Chris Bradley
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Re: EXP: A New Year's treat; Crimzon doughnuts.

Post by Chris Bradley » Sat Jan 02, 2010 9:44 pm

Carl Willis wrote:
> The discharge appears very red in the photo. Just looking at it by eye, does it appear this color?
As mentioned, at slightly higher powers then the colour appears to shift a little towards orange. I guess that some electron recombination begins to creep in. Anyhows, I did sellotape a cheap diffraction filter onto the camera lens and I obtained the following spectrum (that is to say, for slightly higher power/voltage inputs).

Looks much like water and nitrogen would, I think?
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Re: EXP: A New Year's treat; Crimzon doughnuts.

Post by Chris Bradley » Sat Jan 02, 2010 9:52 pm

Carl Willis wrote:
> The discharge appears very red in the photo. Just looking at it by eye, does it appear this color?

I've dug up another photo for you to eyeball.

So this is the slightly higher power that I took that spectrum off of.

All 0.1W of input!!! (2000V and 50uA, or so)

These higher voltages seemed to generate electron emissions around the outer electrodes themselves. And, in fact in this image you can see a little trail of electrons that has punctured the teflon around the magnets and has created some sort of discharge channel there. (and maybe this will show that the 'blues' are actually being represented in the image).

The image is looking along (parallel) to one of the electrodes. You can see another electrode directly facing you, and we're peeking from just beind one. The toroid becomes more 'square' as it closes up on the electrodes (the e-fields are less axi-uniform than towards the middle) so that we're looking 'along' a somewhat straighter section of the toroid.

If the voltage is ramped, the containment edge reaches the electrode and 'tick' - we get regular gas discharge fireworks and the current and power will 'shoot through the roof' (if not limited).
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