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

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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 10:55 pm

Hi Chris,

>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?

The ions might reach 1 keV if they were formed at the center and made it to the cathode. If they are not found at the cathode radius, and did not originate at the center, then there's no reason to assume they are 1-keV ions. I was pointing out that this number is an assumption. As such, I do discourage putting too much credence in it.

>Is there some other way of doing the measurement you envisage?

I suggest setting this up with an oscilloscope that looks at the voltage drop across an appropriately-sized resistor in the power supply lead. Under voltage / pressure conditions where no steady-state discharge current flows, the transient current in the resistor is due electrode and wire capacitance when the sauce is turned on. Under conditions where the discharge forms, the current in the resistor would be the sum of the capacitive current previously measured, leakage current from the discharge, and current corresponding to the buildup of charge in the trap. The time integral of the trap-charging component would be a ballpark measure of trapped charge.

I can't be a backseat driver on such an experiment, I can't troubleshoot it, I can't guarantee it is easy or doable, I can only make the suggestion in general terms. The take-home message is simply that if you come up with a method of measuring trapped charge, that number would be infinitely preferable to assuming your design value by default.

I like the photos. It's a pretty discharge, and the magnetron is a fresh departure from the more-usual fusors and ion sources that fill the annals of this forum.

-Carl
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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 11:31 pm

Carl Willis wrote:
> The ions might reach 1 keV if they were formed at the center and made it to the cathode. If they are not found at the cathode radius, and did not originate at the center, then there's no reason to assume they are 1-keV ions.
Indeed I agree not to make that assumption, but I hope, in due course, I will sufficiently explain to your satisfaction why ions formed anywhere in the device may attain that drive potential. And I repeat and reaffirm my caveats above - don't let me bias what you think at this stage.

Though - I would still be interested to hear your answer to this question; what else would orbit at 4cm radius in a B=0.15T field? Also, why else might we see such a structure?


> I was pointing out that this number is an assumption. As such, I do discourage putting too much credence in it.
I am currently looking to find a way [within my means] to disprove that it is so. It is not yet disproved.


> I suggest setting this up with an oscilloscope that looks at the voltage drop across an appropriately-sized resistor in the power supply lead. Under voltage / pressure conditions where no steady-state discharge current flows, the transient current in the resistor is due electrode and wire capacitance when the sauce is turned on. Under conditions where the discharge forms, the current in the resistor would be the sum of the capacitive current previously measured, leakage current from the discharge, and current corresponding to the buildup of charge in the trap. The time integral of the trap-charging component would be a ballpark measure of trapped charge.
I can do that. Not sure I quite understand why that is so definitive, but I will try to reconcile these measurements with this suggestion.


> I like the photos. It's a pretty discharge, and the magnetron is a fresh departure from the more-usual fusors and ion sources that fill the annals of this forum.
I'm glad, and I hope it's made your day (in particular!).

Again, to reaffirm my previous comments, I am not stating all that I could about this experiment just yet as I am unsure about much of it myself. This was [hopefully] just a 'spoiler' for things to come, and to get the year off on the right footing for the forum.

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

Post by Steven Sesselmann » Sun Jan 03, 2010 12:35 am

Chris,

Congratulations on some fine work, nice to see some new ideas.

The picture in the above post, looks amazing, are the boundaries of the toroid as sharp as they look?

I can see a sharp red boundary, giving the impression that it is tube like.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

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

Post by Chris Bradley » Sun Jan 03, 2010 12:56 am


yes, generally this is what you see, but in the case of this last photo, you are looking down through a very straight part of this thing and so it is a little misleading. I took the pic just to show it wasn't a discharge in direct contact with the electrode, and at this particular point it followed the (flat) electrode, so you're looking through, as you say, a tube-like section of a few cm of the stuff.

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

Post by Chris Bradley » Sun Jan 03, 2010 1:12 am

Carl Willis wrote:
> I suggest setting this up with an oscilloscope that looks at the voltage drop across an appropriately-sized resistor in the power supply lead. Under voltage / pressure conditions where no steady-state discharge current flows, the transient current in the resistor is due electrode and wire capacitance when the sauce is turned on. Under conditions where the discharge forms, the current in the resistor would be the sum of the capacitive current previously measured, leakage current from the discharge, and current corresponding to the buildup of charge in the trap. The time integral of the trap-charging component would be a ballpark measure of trapped charge.

I've just run what I thought was your suggestion but I'm not sure I really follow the applicability (now that I've done it).

At the highest pressures this thing appears at, around 20 microns, (above which you get both regular and 'odd' gas discharges, in my particular setup at the moment) the maximum current to which there is no visible thing happening, as measured by a DVM across a 470ohm load, is 6.8uA. The minimum current for which there is something visible is 7.7uA. Above that, the current will ramp up as much as you want unto >200uA when you start getting discharge modes again.

At the lower pressures of operation (around 1 micron), there is much the same delta but higher currents - with 9.7uA max current for nothing to appear and 11uA for the minimum current for something.

As I say, not sure this quite applies because (forgot to mention, amongst many other details) it appears you can set both voltage and limit current independently. A given voltage doesn't necessarily draw a given current, unless you permit it to, so it appears, which is again why I say it is not a discharge plasma. Not sure if that is a characteristic of my power supply, but basically you can dial in the voltage you want (within the range for which it works) then you can independently set the current limit, and it is quite happy and steady state is possible for a wide range of V and I settings. All that changes is the position, and the visible intensity, of the emissions. Whether there is some high frequency current switching going on unseen, I do not know, but it doesn't look like there is.

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

Post by DaveC » Sun Jan 03, 2010 3:17 am

I don't want to be a "heavy" - here, but Chris - What is it that we are looking at? The pictures are very pretty.... I think from your discussion that you've built something that has a single central rod electrode ( that we can't really see) with four other electrodes arranged around the central axis, at some relatively small distance out from the central electrode. The space around all this is filled with a magnetic field established by permanent magnets (presumably) creating an axial magnetic field(?) of how strong, how uniform? The magnets are at ground potential (?) making some kind of radial electric field, which bumps around the rod cage.

Your explanation suggests that ions are produced by the four plus one central electrode assembly, which then circulate in the axial magnetic field. The ions do not recombine, per your explanation, but essentially produce molecular ionization (or excitation) of other neutrals, whose relaxation from their excited state is the source of the deep red glow we see???

Am I even close to understanding the experiment, you're doing?

A simple circuit and hardware diagram would go nicely here, to help appreciate all that's happening.

Did you say what the gas was? Deuterium, Oxygen, Hydrogen...or ???

Sorry to be a bit sluggish here.

Dave Cooper

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

Post by Steven Sesselmann » Sun Jan 03, 2010 7:20 am

Dave,

Chris has already answered many of the questions you ask in his prevoius posts. If you follow the links in the first post in this thread. Chris gives specific information about the magnetic field, and the assembly of the apparatus.

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

Post by Quantum » Sun Jan 03, 2010 8:28 am

Steven,

I think a lot of the confusion here arises from Chris's explanation of a design that originally consisted of magnets for confinement, then had five electrodes added, and is 'operating; in 'demo mode'(?), with magnets and electrodes, but will not have magnets in it's final form, so will consist of five electrodes.

Chris has often talked of combined magnetic/electrostatic confinement in the past, as being the key to improved efficiency in a fusor.

I think what Dave is asking for, and what would help a lot of people to follow this experiment, is a simple, brief explanation, with a 'diagram', of the method and objectives, rather than having to search through endless links to 'pick out' the relevant information.

In short, a 'brief summary',

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

Post by Chris Bradley » Sun Jan 03, 2010 12:04 pm

Dave Cooper wrote:
> Am I even close to understanding the experiment, you're doing?

No, you're not close - you're bang on! Clearly I have said enough for you to comprehend it!

In regards the details of the conditions, as Steven says I have said all of this but will re-iterate these points so as to confirm them, and also add them to the extant 'summary' at the top:

Mag field = 0.15T, variation across device <5%, background; air, 1 to 20 microns controlled by a metered leak whilst running the turbo unthrottled (i.e. high through-put flow rates).

I guess I'm just concerned that the 'summary' might end up getting too long and someone will then want me to summarise the summary! This isn't a trivial experiment and has taken two years for me to get it all together (partly because I didn't know what it was supposed to look like!! - I have no plans to build to, I'm out on a limb here and 'winging it' as I go...).

You might begin to note that I have scattered the background to this amongst my posts over my 20 months of posting (yes, it's only been that long since I appeared here!). I guess about 30% of my posts directly or indirectly relate to this device, and I will create an anthology of those posts with some text to gel them together at some later stage, if it turns out to be worthwhile to do so. I was essentially aiming to provide background and build up understanding of my plans here these last 20mths before springing this on you, hence you will have to go rummage around if you want the fullest insight ahead of me creating a 'compiled works'!

On the matter of what I've set up for the e-fields: basically, I'm gonna flat out dodge the question! This is because I don't really know. I could say all that I am doing, but then that'd be another long post of speculated theory, and this was just to be some pretty pictures in Images du Jour. So please treat the subject of this thread as just that - mainly pretty pictures.

I've given a taster for where I think the theory sits just to give it sufficient context that they aren't abstract images, but as and when I have some level of ability to say with greater knowledge and insight than you, *then* I will discuss it further. For now, you may well guess better than me.

The reason that I'm not yet going to discuss what the e-fields are up to is because there are many many dielectric surfaces in this, some of which regularly break down (!) and therefore presumably many might be running in dark discharges without me noticiing. There is also plenty of electrode surface. So, taken altogether, I anticipate there are multiple sheath interactions and discharge processes going on which may dominate the e-field behaviour. I am therefore making many multiple alterations to the experiment to see what makes a difference and what those differences are. I don't think it is appropriate to speculate, then, beyond the most cursory 'working-explanation' of what we might be seeing in these photos.

I hope that properly gives the right level of 'caveat' coverage for now!

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

Post by Carl Willis » Sun Jan 03, 2010 8:07 pm

Hi Chris,

Well, the applicability would be to establish (A) that your magnetron does in fact trap some charge, (B) that it traps a particular quantity of charge, and (C) ultimately it would motivate scientific conclusions about particle density and circulating current along the lines of the numbers you came up with earlier by a daisy-chain of questionable assumptions.

What did your experiment entail, and what were the results? Are you able to capture a 'scope trace of the inrush current and post it?

For reference, attached is a figure from Greaves R., Phys. Rev. Letters 74, p. 90-93 (1995). The experiment has something to do with argon ions in a Penning trap, and they measure the trap filling by looking at the power supply current. The inset in the figure is a raw 'scope trace. The main figure is stored charge versus trap potential. For them, the kind of experiment I mentioned yielded useful data (though it has a lot of uncertainty as the error bars show). Your mileage may vary. This approach may not be useful in your situation.

-Carl
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