On subsequent scattering into the grid - absolutely, fully agree; alluded to in my comment "let down by...non-fusing lossy collision interactions".
My point being that you *can* get [at least some of] the fuel ions to where you want them and to the energy you want to get them in a fusor, just like a Polywell I am sure.
The next question, as you rightly highlight, is 'so what happens next' and my point is that in this what-happens-next stage of operation, the Polywell does nothing I can see which gives it some superior status in respect of p11B that any other system that is just about to experience a shed-load of scattering losses, into the grid or wherever else they may be deflected.
If the Polywell 'does fusion' better than a fusor - great! I've no issue with contesting that. I'm not yet convinced though [*after reading lots of documents on it in this forum and public domain*], but could be easily persuaded.
What I don't buy is the curious 'conclusion by habitual use' that the Polywell has a particular benefit for advanced fusion fuels. It is the same distraction of puffery which has lead to the critisism earlier in the post of those who actually believe it! It may cause to degrade and ridicule the work in the eyes of the establishment, and there is no need for that. The Polywell only needs to be talked about with reference to its fusing ability, DD, DT, whatever, but majoring on p11B is a dubious distraction that may cause potentially interested and valuable institutional contributors from passing it by.
Lastest teaser on the Pollywell
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Chris Bradley
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Dan Tibbets
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Re: Lastest teaser on the Polywell
Here is an attempt on my part to expose my ignorance, but...
The whole concept of the polywell is to avoid the difficulty of confining ions with a magnetic field (bassed on mass, an electron weighs ~ 1/4000th of a proton) and to minimize the electron losses of electrostic devises. The ions are not contained (significantly?) by the magnetic field. The magnetic field confines the electrons and the electrons confine the ions. In that regard the device is like a electrostic Farnsworth fuser. The key is that the magnents replace the wire grid so that there is ideally no practical surface for the electrons to hit. After 15 years or so Bussard found that was still not enough as the magnents did not adiquatly confine the electrons . That is where the geometry of the WB 6 came into play. Due to complicated effects of the magnetic fields, the electrons that do escape do so at the 'cusps', and since the magnetic field exists outside the magnents as well as inside, there is sufficient field strenth to curve the path of the escaped electrons untill the they renter through the central holes of the magnets
As far as doing this in a torus, I assume that it doesnt work unless you are in a near sherical condition. That way the energy that is used to accelerate the ions towards the center is recovered as they deccelerate towards the the walls. I don't know why that wouldn't work in a torus , as the ions would be moving as a sine wave patern around the center of the torus ring while orbiting within the torus. I'm guessing it has to do with Maxwellian distribution of the ion energies (ie: there are alot of ion to ion collisions that averages their energy. In a spherical configuration the ions spend most of their time in the less populated outer regions of the reacter so that there is less collisions, and less mixing of energy. If I'm using the terms correctly, a collision could downscatter an ion so that it decreases the likelyhood of having a succesful fusion generating collision, or if upscattered it could have sufficient energy to escape containment. Also, apparently wastfull Bremustung (sp ?) (X-ray) radiation is much worse in the torus because the neutral plasm (ions and electrons) are all moving rapidly, and the radiation comes from the fast moving (hot ) electrons. In the polywell it is not a neutal plasma as there are excess electrons in the center and the electrons are aparently cool (moving slowly) in the dense center and and hot in the less dense perifery. I don't know why this would be but it would minimise the radiation losses.
And, finally there is is 'edge anealing' in the polywelll. Again I don't know how this works but apparently it essentially resets the ion energies to a near equal value near the magnets so that the ions have ~ the same energy as they start accelerating back towards the center, thus decreasing the Maxwellian distribution effects .
Certainly Bussard and associates certainly have explored the various hurdles towards breakeven fusion and Bussard at least has claimed that they have solved all of them. Various parameters such as ion containment time, electron containment time, size effects, radiation losses, etc have been measured (?), and the results can be pluged into formulas that predict the yeild. That they obtained a few detectable neutrons in their relatively low powered (not counting the magnets) breif runs in late 2005 apparently validates their claims. The current work on the WB 7 is hopefully repeating the earlier results with alot more precision and data.
I wonder, since the mechanism of fusion is the same in the polywell as in the fuser, could the claimed scaling laws be demonstrated in amatuer fusers? . Perhaps many orders of magnidued less efficient but showing the same trends?
Dan Tibbets
The whole concept of the polywell is to avoid the difficulty of confining ions with a magnetic field (bassed on mass, an electron weighs ~ 1/4000th of a proton) and to minimize the electron losses of electrostic devises. The ions are not contained (significantly?) by the magnetic field. The magnetic field confines the electrons and the electrons confine the ions. In that regard the device is like a electrostic Farnsworth fuser. The key is that the magnents replace the wire grid so that there is ideally no practical surface for the electrons to hit. After 15 years or so Bussard found that was still not enough as the magnents did not adiquatly confine the electrons . That is where the geometry of the WB 6 came into play. Due to complicated effects of the magnetic fields, the electrons that do escape do so at the 'cusps', and since the magnetic field exists outside the magnents as well as inside, there is sufficient field strenth to curve the path of the escaped electrons untill the they renter through the central holes of the magnets
As far as doing this in a torus, I assume that it doesnt work unless you are in a near sherical condition. That way the energy that is used to accelerate the ions towards the center is recovered as they deccelerate towards the the walls. I don't know why that wouldn't work in a torus , as the ions would be moving as a sine wave patern around the center of the torus ring while orbiting within the torus. I'm guessing it has to do with Maxwellian distribution of the ion energies (ie: there are alot of ion to ion collisions that averages their energy. In a spherical configuration the ions spend most of their time in the less populated outer regions of the reacter so that there is less collisions, and less mixing of energy. If I'm using the terms correctly, a collision could downscatter an ion so that it decreases the likelyhood of having a succesful fusion generating collision, or if upscattered it could have sufficient energy to escape containment. Also, apparently wastfull Bremustung (sp ?) (X-ray) radiation is much worse in the torus because the neutral plasm (ions and electrons) are all moving rapidly, and the radiation comes from the fast moving (hot ) electrons. In the polywell it is not a neutal plasma as there are excess electrons in the center and the electrons are aparently cool (moving slowly) in the dense center and and hot in the less dense perifery. I don't know why this would be but it would minimise the radiation losses.
And, finally there is is 'edge anealing' in the polywelll. Again I don't know how this works but apparently it essentially resets the ion energies to a near equal value near the magnets so that the ions have ~ the same energy as they start accelerating back towards the center, thus decreasing the Maxwellian distribution effects .
Certainly Bussard and associates certainly have explored the various hurdles towards breakeven fusion and Bussard at least has claimed that they have solved all of them. Various parameters such as ion containment time, electron containment time, size effects, radiation losses, etc have been measured (?), and the results can be pluged into formulas that predict the yeild. That they obtained a few detectable neutrons in their relatively low powered (not counting the magnets) breif runs in late 2005 apparently validates their claims. The current work on the WB 7 is hopefully repeating the earlier results with alot more precision and data.
I wonder, since the mechanism of fusion is the same in the polywell as in the fuser, could the claimed scaling laws be demonstrated in amatuer fusers? . Perhaps many orders of magnidued less efficient but showing the same trends?
Dan Tibbets
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Dan Tibbets
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Re: Lastest teaser on the Polywell
"Why doesn't the polywell attempt to make a deep enough electron well to electrostatically confine the ions to a space *within* the coil array?"
I beleive that is percisely what they are doing in a sense. In a typical Farnsworth Hirsh fuser there is a central negatively charged grid that the ions accelerate past on their way to the center. A variation of the fuser design by Tuck ( I hope I am remembering the name right) replaced the central negatively charged grid with a periferal positively charged grid that would repel and accelerate the ions towards the center. But, due to scattering there would always be enough ions traveling fast enough to hit the periferal grid/ shell. In the polywell the electrons are concentrated enough into the center via the magnetic field (and despite the positively charged periiferal grid) that the ions oscillate through the center without ever reaching the outer grid.
I havn't seen any mention of the relitavely importance of the periferal positively charged grid compared to the magnet in containing the pos. ions and accelerating them towards the center. is it insignificant, 1%, 10%, 50% ?
And, to further confuse others and myself, let me speculate on my understanding of the 'anealing' process. As the pos. charged ions approach the positively charged outer grid (magrid) they decelerate untill they stop and begin falling back towards the center(pushed by the positively charged magrid and pulled by the central electrons). Or, if they have excess energy due to upscattering, as they come close to the magrid they are pushed laterally by the magnetic field, effectively converting outward motion to lateral motion. The positvely charged grid then has plenty of time to push them away. This would convert the excess energy ions to the same energy as the ions that would just fall short of kissing the grid if there was no magnetic field. This would 'aneal' the high energy ions back to a baseline at the expense of magnetic energy. I don't think it would have any significant effect on the slower ions . But it would chop off the ions in top half of the bell curve (maxwellian distribution) and give them the energy of the peak of the curve (in an appropriatly tuned system). This would not give a single energy distribution but it would considerably decrease the range and increase the control of the distribution.
This begs the question of how the magnetic field 'pushes' the electrons into the center of the polywell sinse charged particles spiral along magnetic field lines, not get pushed away perpendicurly. I assume that the key is that the electrons are first propelled into the center via an electron gun, then when thy try to leave, their outward motion is converted into lateral motion by the magnetic field, so they form a shell of negative charge. Sort of like a planet orbiting a star, except opposite forces. The planet orbits because its linier velocity is bent by the attractive force of gravity, while the electron orbits because of the 'repulsive' resistance to jumping of field lines. What is going on at the cusps where the electron can escape by following the more perpendicular field lines is less clear to me. I can see how thay would follow the field lines all the way around, back through the center of the magnet, bit why don't all of the electrons eventually end up in this distribution? I supose the mutual repulsion between electrons would prevent them from concentrating in these areas to much.
And finally, the emphasis on the magnetic containment of electrons as the key to the polywell is only a part of the story. It is actually a carefully managed relationship between electrical and magnetic confinement that compliments each other.
Am I close on at least some of my speculations , or out in left field? Comments?
Dan Tibbets
I beleive that is percisely what they are doing in a sense. In a typical Farnsworth Hirsh fuser there is a central negatively charged grid that the ions accelerate past on their way to the center. A variation of the fuser design by Tuck ( I hope I am remembering the name right) replaced the central negatively charged grid with a periferal positively charged grid that would repel and accelerate the ions towards the center. But, due to scattering there would always be enough ions traveling fast enough to hit the periferal grid/ shell. In the polywell the electrons are concentrated enough into the center via the magnetic field (and despite the positively charged periiferal grid) that the ions oscillate through the center without ever reaching the outer grid.
I havn't seen any mention of the relitavely importance of the periferal positively charged grid compared to the magnet in containing the pos. ions and accelerating them towards the center. is it insignificant, 1%, 10%, 50% ?
And, to further confuse others and myself, let me speculate on my understanding of the 'anealing' process. As the pos. charged ions approach the positively charged outer grid (magrid) they decelerate untill they stop and begin falling back towards the center(pushed by the positively charged magrid and pulled by the central electrons). Or, if they have excess energy due to upscattering, as they come close to the magrid they are pushed laterally by the magnetic field, effectively converting outward motion to lateral motion. The positvely charged grid then has plenty of time to push them away. This would convert the excess energy ions to the same energy as the ions that would just fall short of kissing the grid if there was no magnetic field. This would 'aneal' the high energy ions back to a baseline at the expense of magnetic energy. I don't think it would have any significant effect on the slower ions . But it would chop off the ions in top half of the bell curve (maxwellian distribution) and give them the energy of the peak of the curve (in an appropriatly tuned system). This would not give a single energy distribution but it would considerably decrease the range and increase the control of the distribution.
This begs the question of how the magnetic field 'pushes' the electrons into the center of the polywell sinse charged particles spiral along magnetic field lines, not get pushed away perpendicurly. I assume that the key is that the electrons are first propelled into the center via an electron gun, then when thy try to leave, their outward motion is converted into lateral motion by the magnetic field, so they form a shell of negative charge. Sort of like a planet orbiting a star, except opposite forces. The planet orbits because its linier velocity is bent by the attractive force of gravity, while the electron orbits because of the 'repulsive' resistance to jumping of field lines. What is going on at the cusps where the electron can escape by following the more perpendicular field lines is less clear to me. I can see how thay would follow the field lines all the way around, back through the center of the magnet, bit why don't all of the electrons eventually end up in this distribution? I supose the mutual repulsion between electrons would prevent them from concentrating in these areas to much.
And finally, the emphasis on the magnetic containment of electrons as the key to the polywell is only a part of the story. It is actually a carefully managed relationship between electrical and magnetic confinement that compliments each other.
Am I close on at least some of my speculations , or out in left field? Comments?
Dan Tibbets
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Dan Tibbets
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Re: Lastest teaser on the Polywell
Well, it appears that I was not in left field. I was in the left field bleachers. I didn't consider that the MaGrids were donuts, so the ions couldn't be stoped by them where the holes were. After rescaning the paper by Bussard
http://www.askmar.com/ConferenceNotes/2 ... 0Paper.pdf
the only mention I saw for the positive potential on the MaGrid was to slow down and reverse the electrons that had escaped magnetic containment so that they would not hit the vacuum chamber wall. Apparently the ions are contained far enough within the MaGrids that the positive potential is not significant compared to the electron well.
DAn Tibbets
http://www.askmar.com/ConferenceNotes/2 ... 0Paper.pdf
the only mention I saw for the positive potential on the MaGrid was to slow down and reverse the electrons that had escaped magnetic containment so that they would not hit the vacuum chamber wall. Apparently the ions are contained far enough within the MaGrids that the positive potential is not significant compared to the electron well.
DAn Tibbets
Re: Lastest teaser on the Polywell
An ion within a grid that surrounds it on all sides with the same potential is neither attracted nor repelled by it.
As I understand the polywell, the electric field within the magnetic field confines a large proportion of the electrons in the centre which creates a well that confines the ions.
Electrons are attracted by the electrostatic field and follow field lines which converge near the centre. Low velocity electrons are confined by the magnetic bottle effect (converging field lines can reflect electrons/ions)
This is not unlike the Hirsch/ Meeks but avoids grid collisions by magnetic deflection.
Dustin.
As I understand the polywell, the electric field within the magnetic field confines a large proportion of the electrons in the centre which creates a well that confines the ions.
Electrons are attracted by the electrostatic field and follow field lines which converge near the centre. Low velocity electrons are confined by the magnetic bottle effect (converging field lines can reflect electrons/ions)
This is not unlike the Hirsch/ Meeks but avoids grid collisions by magnetic deflection.
Dustin.
Re: Lastest teaser on the Polywell
Brett,
You ask, "Why doesn't the Polywell attempt to make a deep enough electron well to electrostatically confine the ions to a space *within* the coil array?"
That is exactly what it does! Anybody who says otherwise is missing the whole point! Any ion that ever picked up enough energy to get outside the magrid would be gone to the walls, lickity-split, repelled by the positive charge on the magrid relative to the walls.
You ask, "Why doesn't the Polywell attempt to make a deep enough electron well to electrostatically confine the ions to a space *within* the coil array?"
That is exactly what it does! Anybody who says otherwise is missing the whole point! Any ion that ever picked up enough energy to get outside the magrid would be gone to the walls, lickity-split, repelled by the positive charge on the magrid relative to the walls.
Re: Lastest teaser on the Polywell
I guess I must have been misled by talk about ions "circulating" around the magnets. It was obvious to me that if you actually did have circulation around the magnets, you'd lose your ions to the supporting structure, which unlike the magnets themselves, HAS to cut across field lines.
I'm still not clear on why you couldn't accomplish the same thing using a toroidal geometry. Guess I've got some more studying to do.
I'm still not clear on why you couldn't accomplish the same thing using a toroidal geometry. Guess I've got some more studying to do.
Re: Lastest teaser on the Polywell
Frank S. wrote:
> Carl,
>
> You have made me think about why I have such a knee jerk reaction to posts of polywell and you have hit on it precisely. The science interests me and it is as valid as any other approach out there.
>
> My negative reaction is precisely because of sycophants! Go tell it on the mountain. Scream it at the top of your lungs. Have no idea what the hell you are talking about but scream it anyway. Some of the followers are not scientists or even psudoscientists. They border on cult following, idol worship, or religious fanatisim to Bussard and the polywell.
>
> I feel that EM2 is trying to good science. Personally I do not see any blazing benefit to the approach but as I said, it is a path to be explored. When more concrete data is presented the effacacy of the approach will be more clear. Unfortunately my reaction from the groupie fanaticism degrades even the word polywell. A shame for all.
>
> Frank S.
I propose we focus on bigger things than fusion. We could start with changing human nature. There might be some real value there. We could rid the world of fanaticism once and for all. And all those cult worshipers.
> Carl,
>
> You have made me think about why I have such a knee jerk reaction to posts of polywell and you have hit on it precisely. The science interests me and it is as valid as any other approach out there.
>
> My negative reaction is precisely because of sycophants! Go tell it on the mountain. Scream it at the top of your lungs. Have no idea what the hell you are talking about but scream it anyway. Some of the followers are not scientists or even psudoscientists. They border on cult following, idol worship, or religious fanatisim to Bussard and the polywell.
>
> I feel that EM2 is trying to good science. Personally I do not see any blazing benefit to the approach but as I said, it is a path to be explored. When more concrete data is presented the effacacy of the approach will be more clear. Unfortunately my reaction from the groupie fanaticism degrades even the word polywell. A shame for all.
>
> Frank S.
I propose we focus on bigger things than fusion. We could start with changing human nature. There might be some real value there. We could rid the world of fanaticism once and for all. And all those cult worshipers.
Re: Lastest teaser on the Polywell
"please continue to support it but direct your excitement to the substance of the science, not to the salespitch."
As I recall the whole fusor thing got started because of a Bussard sales pitch.
There are still different levels of buy in.
As I recall the whole fusor thing got started because of a Bussard sales pitch.
There are still different levels of buy in.
Re: Lastest teaser on the Polywell
Well that was a pretty safe bet.
A continuous run is going to require some hefty power supplies and magnet cooling.
I estimate the cost of buying all the eqpt new at $5 to $25 mill. No doubt scroungers with a very big garage could do it for less.
A continuous run is going to require some hefty power supplies and magnet cooling.
I estimate the cost of buying all the eqpt new at $5 to $25 mill. No doubt scroungers with a very big garage could do it for less.
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Carl Willis
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Re: Lastest teaser on the Polywell
>I propose we focus on bigger things than fusion. We could start with changing human nature. There might be some real value there. We could rid the world of fanaticism once and for all. And all those cult worshipers.
I propose that we focus, as we always have on this forum, only on the science and technology of amateur fusion. Anything else belongs somewhere else. The fact that this venue has limited scope does not mean that the same limitations need to be imposed on the world at large.
After all, not everybody in the world is interested in building fusion devices. Some people just like to jawbone about fusion devices. Other folks have not the slightest whit of intellectual interest in fusion devices, but do have an interest in money, for instance; or their egos. Congratulations to 'em. All I ask is that they just hock their loogie elsewhere.
-Carl
I propose that we focus, as we always have on this forum, only on the science and technology of amateur fusion. Anything else belongs somewhere else. The fact that this venue has limited scope does not mean that the same limitations need to be imposed on the world at large.
After all, not everybody in the world is interested in building fusion devices. Some people just like to jawbone about fusion devices. Other folks have not the slightest whit of intellectual interest in fusion devices, but do have an interest in money, for instance; or their egos. Congratulations to 'em. All I ask is that they just hock their loogie elsewhere.
-Carl
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Richard Hull
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Re: Lastest teaser on the Polywell
Back to the issue of the polywell and linking it to the old old ion gunned Farnsworth systems.
What is the actual working pressure of deuterium in the polywell chamber??? Do we know precisely?
Our little fusors are at significant pressures, ( >10 microns)
The cave fusor of Hirsch ran at 10e-6 torr in the inner grid! If the Polywell is at a similar vacuum during run time, then it is a scientific device and not a deuterium gas lamp like our fusors. Getting rid of all debris like other D2 gas atoms in a confinement zone will improve fusion chances of occuring where theory says and not where chance dictates.
Is this just a matter of pressure reduction allowing theory to have a chance all around? If so, then most any idealized deep vacuum system will do better on a ion-ion generational basis.
What is the operational pressure of the polywell.................Tom?
Richard Hull
What is the actual working pressure of deuterium in the polywell chamber??? Do we know precisely?
Our little fusors are at significant pressures, ( >10 microns)
The cave fusor of Hirsch ran at 10e-6 torr in the inner grid! If the Polywell is at a similar vacuum during run time, then it is a scientific device and not a deuterium gas lamp like our fusors. Getting rid of all debris like other D2 gas atoms in a confinement zone will improve fusion chances of occuring where theory says and not where chance dictates.
Is this just a matter of pressure reduction allowing theory to have a chance all around? If so, then most any idealized deep vacuum system will do better on a ion-ion generational basis.
What is the operational pressure of the polywell.................Tom?
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Chris Bradley
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Re: Lastest teaser on the Polywell
Was there an answer to Richard's last question? I am interested to know what the operational pressures are for the Polywell design, and can find nothing on the talk-polywell site.