regarding recirculation

Discuss how polywell fusion works; share theoretical questions and answers.

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KitemanSA
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Postby KitemanSA » Tue Jul 19, 2011 3:36 am

jcoady wrote: I think the term recirculation refers to the electron moving moving around inside polywell and doesn't necessary refer to the electron moving outside of the polywell and coming back inside. Here is a paper by Bussard about recirculation.
That is quite a old paper. Read the Valencia Paper (link below). It should be clear that at the end he distinguishes between transits and recirculation. (Of course it has been a while so I hope I haven't just deposited my foot orally! :wink:

http://www.askmar.com/ConferenceNotes/2 ... 0Paper.pdf

(Corrected spelling)
Last edited by KitemanSA on Wed Jul 20, 2011 11:27 am, edited 1 time in total.

D Tibbets
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Postby D Tibbets » Tue Jul 19, 2011 10:27 pm

jcoady, Recirculation indeed refers to electrons being recirculated (probably through the same cusp after they escape through a cusp to the space outside the magrid. The magrid in most of the Polywells had a positive charge on the magrid. This positive charge serves to accelerate the electrons from the electron guns ( the guns in this configuration only emitted low energy electrons by thermogenic means- perhaps at ~ 12 V). My understanding is that this electrostatic acceleration of escaped electrons back through a cusp is equivalent to the acceleration of the new electrons from the electron gun. If the escaping electrons have been upscattered too much (>~2,000eV) above the potential well and ~ equal to the potential on the magrid they will be slowed but not reversed. In this case you are both removing nasty upscattered electrons, but most(?) of this upscattered energy is recovered. So the recirculation not only recovers most electrons at very little cost, and impedes progressive electron up scattering at only a modest cost. The magrids are direct energy converts (like those discussed for P-B11 fusion, but these are designed to recover the the energy (most) of the escaping electrons. So long as the electrons have not accumulated to much KE (~ 12 KeV in the WB6 example) the electron will be stoped while transfering the KE to the grid, they will then be acellerated back into the magrid, the energy expendature balance should be very small. The electrons that have more than 12 KeV energy in an outward direction will only retain the fraction above 12 KeV,.

To correct the ion collisions- the ions need a few thousand Coulomb collisions before a fusion collision is likely to occur. To allow annealing to work, only a few coulomb collisions could occur (mostly near the center) or possibly less than one collision on each transit through the Wiffleball space. How many times an ion is likely to transit the system before escape has not been well quantified publicly. It is generally accepted (by us optimists) that the ions transit many more times before loss compared to electrons, in fact Bussard has hinted, that most of the ions may fuse before they escape. This high fuel burn up is needed for several reasons (to limit external vacuum pumping, to minimize ion escape energy losses (the magrid would accelerate the ions as they left which would add to the overall losses)). That Bussard, etel claim that electron losses dominate over ion losses implies that this is the case. It also implies that A. Carlson's insistence on bipolar flow in the cusps cannot exist if the system works.

Dan Tibbets
To error is human... and I'm very human.

happyjack27
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Postby happyjack27 » Fri Jul 22, 2011 12:46 pm

ya, but with a positively charged grid you also increase the rate as well as energy of electrons lost to the grid. and you've actually increased their energy by quite a bit. as they're not just going straight into the grid they're spiraling around in tight circles in the magnetic field, so they're actually going a lot faster. so ultimately it's a trade off of loss mechanisms. and thus as with all trade-offs you have to find the proper balance; the minimum.

jcoady
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Postby jcoady » Fri Jul 22, 2011 3:18 pm

I updated my web based 3D polywell simulator to take into account the charge on the magrid. Just click the start simulation button to simulate electron trapping in the polywell during startup conditions.

http://members.shaw.ca/johncoady/polywell.html

The electron starts off at a configured location and energy level and is attracted in the direction of a higher electric potential. You can also configure the charge on the magrid to effect how much kinetic energy the electron will get. When the electron exits through one of the cusps, its kinetic energy will decrease and then it will be attracted back into the polywell due to the change in electric potential.

I also calculate the B field, E field and electric potential everywhere in space. You can click the show checkboxes to view these fields.

This simulator uses technology in the latest versions of Google Chrome and Firefox web browsers. So if you have an older version of the web browser you will need to upgrade your browser to view the simulation. If you are using Internet Explorer, you will be prompted to install a plugin from google.

TallDave
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Postby TallDave » Fri Jul 22, 2011 3:31 pm

Fun, thanks for sharing.
n*kBolt*Te = B**2/(2*mu0) and B^.25 loss scaling? Or not so much? Hopefully we'll know soon...

happyjack27
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Postby happyjack27 » Fri Jul 22, 2011 7:24 pm

D Tibbets wrote:To correct the ion collisions- the ions need a few thousand Coulomb collisions before a fusion collision is likely to occur. To allow annealing to work, only a few coulomb collisions could occur (mostly near the center) or possibly less than one collision on each transit through the Wiffleball space. How many times an ion is likely to transit the system before escape has not been well quantified publicly. It is generally accepted (by us optimists) that the ions transit many more times before loss compared to electrons, in fact Bussard has hinted, that most of the ions may fuse before they escape. This high fuel burn up is needed for several reasons (to limit external vacuum pumping, to minimize ion escape energy losses (the magrid would accelerate the ions as they left which would add to the overall losses)). That Bussard, etel claim that electron losses dominate over ion losses implies that this is the case. It also implies that A. Carlson's insistence on bipolar flow in the cusps cannot exist if the system works.
Dan Tibbets


in my em-nbody sims the ions displayed VERY good confinement. I don't think a single ion was ever lost. it was all electron losses. also the ions get progressively slower away from the core so if an ion ever were lost it would be at very low energy. (though it would be at that point being repulsed by the magrid so it would accelerate away, acquiring energy _after_ its past the point of no return.) from what i saw in the sims i wouldn't be surprised if the vast majority of the fuel burned up rather than escaping, even at low fusion rates.

rcain
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Postby rcain » Sat Jul 23, 2011 3:55 am

jcoady wrote:I updated my web based 3D polywell simulator ...

http://members.shaw.ca/johncoady/polywell.html

...

This simulator uses technology in the latest versions of Google Chrome and Firefox web browsers. So if you have an older version of the web browser you will need to upgrade your browser to view the simulation. If you are using Internet Explorer, you will be prompted to install a plugin from google.


I am using latest versions of FF (5.0) and Chrome (12.0) - but neither will display any graphics on that page, just the message: 'Your Browser doesn't support X3DOM
Read more about X3DOM Browser support on:' and the controls.

any ideas?

windmill
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Postby windmill » Sat Jul 23, 2011 1:38 pm

Me too. Same software, same problem.

jcoady
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Postby jcoady » Sat Jul 23, 2011 2:50 pm

The underlying technology used to show 3D in a web page in current versions google Chrome and Firefox web browsers is called webGL . So if webgl works in your web browser on your computer then it should be able to display the 3D polywell simulation. Here is a site from google that has several webgl samples and also a link to a site to check if webgl works on your browser.

http://www.chromeexperiments.com/webgl

http://www.doesmybrowsersupportwebgl.com/

If it doesn't work then maybe your computer's graphics card doesn't have all the graphics features that webgl requires.

rcain
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Postby rcain » Sat Jul 23, 2011 3:09 pm

thanks. same prob. computer says 'Nay' - Platform Win32
Agent Mozilla/5.0 (Windows NT 6.0) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.122 Safari/534.30

i will need to look into this. glad to know i'm not the only one.

Betruger
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Postby Betruger » Sat Jul 23, 2011 6:30 pm

No problem here- Same Chrome version as RCain on Win7 Ultimate 64

hanelyp
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Postby hanelyp » Sun Jul 24, 2011 1:34 am

x3dom claims to support firefox 4. I'm running firefox 5 right now, and x3dom isn't working.

jcoady
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Postby jcoady » Sun Jul 24, 2011 3:49 am

Firefox 5 supports webgl, but you also need graphics hardware in your computer that supports something called "shading" and "hardware accelerated 3D graphics" in order for webgl to work. A lot of older graphics cards don't support shading so webgl will not work on these computers. So if webgl doesn't work in your browser with your computers graphics hardware, then X3DOM won't work either and neither will my polywell 3D simulation.


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