Talk-Polywell.org

Thanks.

NCSUnuke,

Welcome aboard. There are at least a few Nukes (maybe more than a few) who spend time around here. I counted 4 on a topic thread a while back.

TallDave wrote:Agreed. The purpose of WB-8 is to determine B scaling, esp. in terms of confinement.

Given the item is also larger (just noticed this stated on the web site!) they can study size scaling with equal B field too. All they have to do is run the magnets at low power.

New Boyle Article Up. See my blogs or the "Boyle" thread in News.

Here's a noob question for you guys: does the color of the plasma in the WB-7 photo tell you anything about what elements/isotopes are present? I've seen photos of deuterium plasmas in fusors that had a more purplish color. Is the color significant?

billh wrote:Here's a noob question for you guys: does the color of the plasma in the WB-7 photo tell you anything about what elements/isotopes are present? I've seen photos of deuterium plasmas in fusors that had a more purplish color. Is the color significant?

I believe Argon has been used as a test gas. Rick has used it in his POPS experiments. I would not be surprised if he also used it in the Polywell.

MSimon wrote:

KitemanSA wrote:

TallDave wrote: Yes, I've made that point as well. The other scaling questions are so much more important, why screw around with a new geometry at this point when it isn't even an order of magnitude?

Because some new geometries may just solve the electron loss problem.

Or make it worse. (the theory I favor).

What I will just say will be likely stupid, but it just came to my mind and I cannot resist... What about to make coils moving and add some smart balancing electronics to dynamically avoid cusps altogether?

In other words, make geometry dynamic?

AFAIK there will always be cusps where magnetic fields meet.

TallDave wrote:AFAIK there will always be cusps where magnetic fields meet.

Yes, but maybe they could be 'counterbalanced' by moving fields (or maybe just changing fields). I mean that such cusps would be only temporary, dynamically counterbalanced by opposite field just a moment later, perhaps based on some clever feedback loop. But very likely, one issue is that it would have to be too fast...

Luzr wrote: What I will just say will be likely stupid, but it just came to my mind and I cannot resist... What about to make coils moving and add some smart balancing electronics to dynamically avoid cusps altogether?

In other words, make geometry dynamic?

There is no motion you can apply to the magnets that won't appear as stationary to the electrons. Dr. B. said that the 0.4msec pulse in the WB6 experiments seemed steady state to the electrons. Thus you would have to move the magnets at much more than 2500 Hz to even begin to appear dynamical.

MSimon wrote:

billh wrote:Here's a noob question for you guys: does the color of the plasma in the WB-7 photo tell you anything about what elements/isotopes are present? I've seen photos of deuterium plasmas in fusors that had a more purplish color. Is the color significant?

I believe Argon has been used as a test gas. Rick has used it in his POPS experiments. I would not be surprised if he also used it in the Polywell.

bytheby, there are a couple of interesting references to optical analysis in these papers from last years IEC conference:

http://fti.neep.wisc.edu/static/TALKS/1 ... hnkipr.pdf - 'Pulsed IEC - optical diagnostics' - Katchan, et al - using Doppler spectroscopy to assess fast neutrals (amongst other things).

and

http://fti.neep.wisc.edu/static/TALKS/1 ... murali.ppt - esp p27 (Thorson - 'visible light intensity {correlates} with potential structure') - 'Effects of microchanels in (gridded) IEC devices' - Murali, et al.

If the glow is just black body radiation then the color would only tell you the temperature. If it is from the emission spectrum of the gas then perhaps you could infer the composition. The paper you linked was heavy sledding for a non-scientist like me, but it seems to be talking about measuring velocities in a fusor by measuring Doppler shift of the hydrogen alpha spectral line. That implies that the light we see is mainly from the emission spectrum of the neutral gas. So is the characteristic purplish glow I see in many fusor pictures the characteristic color of hydrogen (deuterium)? Is the color visibly different if the gas is helium? And can we tell from the WB-7 picture what gas is present?

There seems to be a bit of confusion about what that right-hand picture is on the EMC2 website, the one with all the flanges and ports.

I don't think this has been mentioned before, but there's a pretty useful clue in the filename.

Right-click the image and select 'view image info': the filename is "WB8.jpg".

hallmh wrote:There seems to be a bit of confusion about what that right-hand picture is on the EMC2 website, the one with all the flanges and ports.

I don't think this has been mentioned before, but there's a pretty useful clue in the filename.

Right-click the image and select 'view image info': the filename is "WB8.jpg".

Heh, good catch. Thanks for sharing.

Bill,

I tried measuring gas velocity in some of the earlier machines. They probably have better diagnostics now, but I had an economy spectrometer from Ocean Optics that I custom-ordered to center on H-beta.

H-alpha is brighter, but is a doublet. To complicate things, the spectrum for deuterium is subtly different from hydrogen, and both are generally present. That crowds things a mite in the ruby red h-alpha area. Another interference is Stark broadening, which occurs at higher density.

H-beta is a singlet. It is blue-green, I think about 486 nm. This one is simpler for measurement of Doppler broadening.

I think I measured fleeting doppler broadening of faint light emissions a couple of times, but the signals were barely detectable and lasted only a second or so. My experiences with bright glows was that they occurred as a result of a Paschen discharge and they were pretty cold compared to desired fusion conditions. Any broadening when the pressure is spiking is also suspect as you must consider Stark. The bright glows are photogenic, but probably past the useful part of the run.

There's a rub to attempting to measure light output from a properly-running low-power Polywell. The thing is, ions emit light during recombination, i.e. when they become useless to the reaction. Ideally, they last indefinitely, emitting no light! The ones you want to see are invisible to a spectrometer or camera.

Edmund carries an H-beta interference filter at my request ... I pointed out how close it was to argon 488. I suspect they sort them by the wavelength they actually work at, and that there might be a market for H-beta. A PMT is more sensitive to blue than red, so detects the H-beta more readiy. I have captured a faint H-beta convergent glow coincident with a deep potential well (directly measured with a Langmuir probe) in one of the early devices. Unless the flux is very high (which WB-7 may well be capable of), I think a faint glow is the actual desired condition.

I finally concluded that neutrons were the most dependable way of detecting fusion conditions, and concentrated on assuring the counters would not make false counts.

My understanding is that Nebel and Park are way better at plasma diagnostics than I am, and almost certainly are bringing better instruments to bear on this thing.