On the question of thermalization of the fusion plasma - it seems to me that there would be a correlation between tendency to thermalize and the probability of a fusion occurring in a given unit volume / time. If alpha products are coming out in random directions, but relatively infrequently, maybe it's not enough to foul the nice mono-energy of the system. Or perhaps there's a probability threshold, past which, the system will tumble over into a thermal mode?
Could this be something that might be modeled, using manageable numbers of particles?
Thermalization & probability of fusion?
Hmmm, not sure how alphas will behave in those conditions. They have very little penetrating power in solids, but I don't know what percentage we would expect to be slowed by electron/ion collisions and how much that might tend to thermalize the system.
Hopefully that's not one of our unanswerables.
Hopefully that's not one of our unanswerables.
Any cross section besides hard sphere (which is obviously inapplicable to coulomb collisions) reduces with speed, because the particles aren't near each other long enough to change course much. I think it very unlikely that a 3MV alpha is going to make much difference compared with all the failed attempts that led up to its production.
I believe it takes 60 D-D passes per fusion.93143 wrote:Any cross section besides hard sphere (which is obviously inapplicable to coulomb collisions) reduces with speed, because the particles aren't near each other long enough to change course much. I think it very unlikely that a 3MV alpha is going to make much difference compared with all the failed attempts that led up to its production.
A lot will depend on the size of and the Mean Free Path (MFP) in the reaction space. Outside it the MFP should be long enough so that the odds of interaction are low.
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If I understand your question - the tendency to thermalize is one of the things the IEC overcomes by trying to maintain a dynamic ion flow, and POPS does it more forcefully. The alphas should add a high energy background noise, and just blow out from the center to the walls where they get most of their energy sucked out. I think we can design it so that the energy extraction is far away from the production and the two problems won't interact too much.
But I'm not sure I understand the question. The whole point of IEC fusion is to not be thermal for fusion to happen.
But I'm not sure I understand the question. The whole point of IEC fusion is to not be thermal for fusion to happen.
It seems to me there are two questions to be answered here.
1) What is the effect of high energy alphas upon core ions? Do they cause upscatter sufficient to blow the core apart (i.e., create large amounts of upscatter), or even to thermalize it?
2) Assuming the answer to (1) is "they escape too quickly to have a significant influence on the core", what is the effect of high energy alphas upon contact with the wiffleball?
1) What is the effect of high energy alphas upon core ions? Do they cause upscatter sufficient to blow the core apart (i.e., create large amounts of upscatter), or even to thermalize it?
2) Assuming the answer to (1) is "they escape too quickly to have a significant influence on the core", what is the effect of high energy alphas upon contact with the wiffleball?
Contact with the wiffleball? Are you referring to the magnetic pressure effect of the outward flow of positive alphas? Should cause the wiffleball to expand or at least wiggle a bit--maybe another (small) cause of instability that leads to the plasma motion some are suggesting actually exists in an IEC machine?scareduck wrote:It seems to me there are two questions to be answered here.
2) Assuming the answer to (1) is "they escape too quickly to have a significant influence on the core", what is the effect of high energy alphas upon contact with the wiffleball?
Tom.Cuddihy
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Faith is the foundation of reason.
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Faith is the foundation of reason.
No, I'm talking about contact with the allegedly cold electrons held captive in the magnetic field. Assume these alphas collide with some of the cold electrons. Will the energy transfer be enough for the electrons to achieve escape velocity from the magrid? And if they do, isn't that another energy loss mechanism you have to deal with?cuddihy wrote:Contact with the wiffleball? Are you referring to the magnetic pressure effect of the outward flow of positive alphas?scareduck wrote:It seems to me there are two questions to be answered here.
2) Assuming the answer to (1) is "they escape too quickly to have a significant influence on the core", what is the effect of high energy alphas upon contact with the wiffleball?
Energy transfer is going to be low because of a mass difference of roughly 7300 to 1.scareduck wrote:No, I'm talking about contact with the allegedly cold electrons held captive in the magnetic field. Assume these alphas collide with some of the cold electrons. Will the energy transfer be enough for the electrons to achieve escape velocity from the magrid? And if they do, isn't that another energy loss mechanism you have to deal with?cuddihy wrote:Contact with the wiffleball? Are you referring to the magnetic pressure effect of the outward flow of positive alphas?scareduck wrote:It seems to me there are two questions to be answered here.
2) Assuming the answer to (1) is "they escape too quickly to have a significant influence on the core", what is the effect of high energy alphas upon contact with the wiffleball?
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In the course of doing more research on the general background of these devices, I encountered a secondary Todd Rider paper, published in 1995 about the same time as his Physics of Plasmas paper "A general critique...", coincidentally in the same volume of that journal, "Modification of classical Spitzer ion-electron energy transfer rate for large ratios of ion to electron temperatures" (Physics of Plasmas vol. 2, p. 1873). Here's an excerpt of the abstract. (I use "{sub}" in variables to denote subscripts.)MSimon wrote:Energy transfer is going to be low because of a mass difference of roughly 7300 to 1.
It goes on from there with more equations, but the basic Spitzer transfer equation looks like this:Corrections to the classical Spitzer heat transfer rate between ions and electrons are calculated for the case when the ion temperature Ti is significantly higher than the electron temperature T{sub}e. It is found that slow electrons are partially depleted by their, interactions with the ions, resulting in a decrease in the heat transfer in comparison with the Spitzer rate, which assumes perfectly Maxwellian electrons. The heat transfer steadily decreases from the classical value as T{sub}i/T{sub}e increases; for T{sub}i/T{sub}e, values of several hundred, the heat transfer rate drops to around 60%-80% of the Spitzer result.
t{sub}g = m^2*v^3/(16*pi*Z^2*Z'^2*e^4*n'*ln(A)) x (v/v'{sub}t)^2/(erf(v/v'{sub}t-(v/v'{sub}t)*erf'(v/v'{sub}t)')
erf() is an error function:
erf(w) = 2/sqrt(pi)*(integral(0,w,e^-w'^2*dw'))
where all the v' terms are from background particles (presumably, he means the ions). Interesting that he predicted the energy transfer would actually be less than the classical model predicted.
Simon, you got me scratching my head. Are you talking about overall density of a particle population or are you talking about mass difference between particles? Or ???Energy transfer is going to be low because of a mass difference of roughly 7300 to 1.
If I hit a cannonball with a BB, energy will be imparted regardless of mass difference.
True. However, the amount of energy is transfered is maximum when the particle masses are equal. The bb is not going to transfer much energy to the cannonball.JohnP wrote:Simon, you got me scratching my head. Are you talking about overall density of a particle population or are you talking about mass difference between particles? Or ???Energy transfer is going to be low because of a mass difference of roughly 7300 to 1.
If I hit a cannonball with a BB, energy will be imparted regardless of mass difference.
When you do motion problems on the surface of the earth the energy transfered to the earth is neglected. Totally.
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This is what I missed out on when I skipped upper division mechanics. This link filled me in:http://www.virginia.edu/ep/Interactions ... matics.htm
We're still left with energy transferred by electric interaction, no?
We're still left with energy transferred by electric interaction, no?
Yes.JohnP wrote:This is what I missed out on when I skipped upper division mechanics. This link filled me in:http://www.virginia.edu/ep/Interactions ... matics.htm
We're still left with energy transferred by electric interaction, no?
It gets complicated when the electrons are cold and the ions are hot. Classical calculations are based on similar energy distributions.
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