Measurements of Ion Energy/Temperature

[Aeronaut]

Most of that went over my head, James. Am I correct in understanding that the ion heating effect you described could possibly apply to the describing and predicting the plasma temperature/ energy level at any point during the axial phase?

[Brian H]

jamesr wrote:

Second, temperature is measured in electron volts, and tiny-ness is FF’s friend

I’m not quite sure how you think the units you measure something in suddenly changes the physics of what going on, but I get your general point.

On a separate topic, one thing I came across today in a talk about astrophysical plasmas, was that in magnetic reconnection (ie where a a twisted or opposing field changes topology), the release of magnetic energy to the particles causes them to be accelerated to supra-thermal speeds. This mechanism of heating ions & electrons as the plasmoid forms could play a crucial role in the dynamics. In that you cannot consider the plasma in the plasmoid as it forms to have a specific temperature, as such, because the dynamic have forced it well out of a Maxwellian thermal distribution. The density and collisionality of the plasma probably means it will thermalise again within a very short time, so it may be insignificant, but then again this seed population of fast ions could propote more fusion, or on the other hand a population of fast electrons created by this process could promote extra bremsstrahlung & have a negative effect.

It seems the more I learn about plasma physics the less you can predict by simple analysis. The only way to really tell is to do a non-linear simulation to test the hypothesis, and even then it only tells you about the particular instabilities/modes that can be accounted for in whatever simplified model you are using.
Yes, I didn’t want to get explicitly into discussing the reason eV are more informative and less “frightening” than talking about billions°, but rather just to communicate that in a very tiny space the energy level of the agitated particles involved was much more plausible and attainable than raising the entire volume of a typical containment vessel’s plasma to such a temp. That is a classic measure of “difficulty” of initiating and maintaining any particular species of fusion, and the basis, it seems to me, of many meso-fusion experts’ skepticism. Which abounds.

As for the brehmstrahlung, I assume you have read the patent and are generally familiar with the claim that Eric et al are making that there is a target quantum gap in which the ‘thermal’ (which I understand to mean essentially ‘by collision’) energy transmission to electrons–which results in X-Ray Band photon emission–does not occur, a kind of notch of opportunity to be exploited. This permits the process to sidestep the “X-ray cooling” standard theory predicts will squelch the p-B11 fusion process long before it can attain unity. (BTW, have you spent any time checking out the proposed X-Scan version of the FoFu, as discussed on the LPP site? It uses a “detuned” generator to produce an X-Ray beam for external scanning of structures, etc.)

And the simulations, 1- and 2-D, etc., which Eric et al were working with were necessarily, I am sure, simplifications. And the only way to tell if the core of what they were trying to demonstrate and extrapolate is real, is real-world plasma-pounding. That is why I made the point that so far, better than ‘so good’; results exceed predictions.

I am definitely not up on the detailed theory or calculations, JR, and admit it openly. Nor do I ‘grok’ the details of Eric’s fundamental disagreement with the Standard Model and astrophysics about the primacy of magnetic phenomena over gravitational ones on the macro scale, and how that translates into nano-scale events. But I observe that this is the bet which is being made, and that it has (to my mind) the pattern and shape of a winning one. And results seem to reinforce that more and more as this “proof of concept” process proceeds.

Whether the results to date explicitly support the “notch” analysis, I don’t know. But I suspect that at the very least they have failed to invalidate it.

[jamesr]

Aeronaut wrote: Most of that went over my head, James. Am I correct in understanding that the ion heating effect you described could possibly apply to the describing and predicting the plasma temperature/ energy level at any point during the axial phase?

most of the heating in the axial phase will still, I think be due to the compression (roughly adiabatic) and and resistive heating. but when you get to the point where the field get so twisted, you can get a release of the energy that is stored in those twists by the field reconfiguring (snapping & reconnecting) with another part of the field to effectively undo the twists.

This heating mechanism though does not accelerate the particles adiabatically, instead you get some ions/electrons with much higher energies.

[Brian H]

jamesr wrote:

Most of that went over my head, James. Am I correct in understanding that the ion heating effect you described could possibly apply to the describing and predicting the plasma temperature/ energy level at any point during the axial phase?

most of the heating in the axial phase will still, I think be due to the compression (roughly adiabatic) and and resistive heating. but when you get to the point where the field get so twisted, you can get a release of the energy that is stored in those twists by the field reconfiguring (snapping & reconnecting) with another part of the field to effectively undo the twists.

This heating mechanism though does not accelerate the particles adiabatically, instead you get some ions/electrons with much higher energies.
Is this (axial phase) prior to the formation of the plasmoid?

[Henning]

The different phases of the DPF:
Axial Phase
Sheath
Plasmoid
See Torulf’s pictures linked behind these descriptions.

[Brian H]

Henning wrote: The different phases of the DPF:
Axial Phase
Sheath
Plasmoid
See Torulf’s pictures linked behind these descriptions.

Ya, that’s what I thought/recalled.

So here’s some of the relevant FF hypothesis re the major heat generation cycle, from the patent:

The higher atomic charge, Z, of B11 greatly increases the x-ray emission rate, which is proportional to Z.sup.2 making it difficult to achieve ignition, e.g., the point at which the thermonuclear power exceeds the x-ray emission. The present invention overcomes these difficulties using a detailed quantitative theory of the plasma focus, described below, and the high magnetic field effect (HMFE). This effect, first pointed out by McNally, involves the reduction of energy transfer from the ions to the electrons in the presence of a strong magnetic field. This in turn reduces the electron temperature and thus the bremsstrahlung emission.

The implication IMO is that almost all of the filament energy is magnetically controlled throughout, and little inductive heating occurs in the axial and sheath phases. Or am I over-interpreting?

[Brian H]

Here’s an article that has set me wondering: http://www.sciencenews.org/view/generic/id/50258/title/Star_outweighed_any_known_in_Milky_Way

The relevant quote:

Theory predicts that any star heavier than the equivalent of 140 suns blows up in a very special way. Photons produced at the core of such a star provide an outward pressure that resists gravity’s inward pull. But when the core temperature exceeds about a billion kelvins, the photons suddenly become energetic enough to annihilate each other and produce pairs of electrons and positrons.

Is such pair instability a possibility in the FF plasmoid, since temps would be in that range?

[jamesr]

Brian H wrote: Here’s an article that has set me wondering: http://www.sciencenews.org/view/generic/id/50258/title/Star_outweighed_any_known_in_Milky_Way

The relevant quote:

Theory predicts that any star heavier than the equivalent of 140 suns blows up in a very special way. Photons produced at the core of such a star provide an outward pressure that resists gravity’s inward pull. But when the core temperature exceeds about a billion kelvins, the photons suddenly become energetic enough to annihilate each other and produce pairs of electrons and positrons.

Is such pair instability a possibility in the FF plasmoid, since temps would be in that range?

Normally for electron-positron pair production, in Compton scattering, you need a photon with at least 1.02MeV (ie twice their rest mass energy of 0.511MeV). I believe, for two photons to annihilate you need to take into account higher order effects of QED, as normally photons do not interact directly with each other, only with charged particles. But the end result is the same, you need a total of 1.02MeV available to create the pair.

Since we are taking about temperatures of 50-100keV you will not really have any x-ray photons with that kind of energy. There may be the odd one created from the energetic fusion products, but nothing significant I would expect.

[Brian H]

jamesr wrote:

Here’s an article that has set me wondering: http://www.sciencenews.org/view/generic/id/50258/title/Star_outweighed_any_known_in_Milky_Way

The relevant quote:

Theory predicts that any star heavier than the equivalent of 140 suns blows up in a very special way. Photons produced at the core of such a star provide an outward pressure that resists gravity’s inward pull. But when the core temperature exceeds about a billion kelvins, the photons suddenly become energetic enough to annihilate each other and produce pairs of electrons and positrons.

Is such pair instability a possibility in the FF plasmoid, since temps would be in that range?

Normally for electron-positron pair production, in Compton scattering, you need a photon with at least 1.02MeV (ie twice their rest mass energy of 0.511MeV). I believe, for two photons to annihilate you need to take into account higher order effects of QED, as normally photons do not interact directly with each other, only with charged particles. But the end result is the same, you need a total of 1.02MeV available to create the pair.

Since we are taking about temperatures of 50-100keV you will not really have any x-ray photons with that kind of energy. There may be the odd one created from the energetic fusion products, but nothing significant I would expect.
So the temp ref in the article is wrong? Interesting.

[jamesr]

Brian H wrote:
So the temp ref in the article is wrong? Interesting.

In the core of a star there are so many photons that cause the radiation pressure that normally balances the gravitational compression. It would only take a slight imbalance of a few of the highest energy photons being used up to form electron/positron pairs to start a cascade. Once the gravitational collapse starts, enormous amounts of potential energy are converted to kinetic. Heating the layer of the star in the process, and so implosion turns to explosion. Depending on the size of the star this could just eject the outer layers or if the collapse proceeds further triggering fusion of heavier elements and you have a huge supernovae.

See: wikipedia – Pair instability supernova

[Brian H]

jamesr wrote:

So the temp ref in the article is wrong? Interesting.

In the core of a star there are so many photons that cause the radiation pressure that normally balances the gravitational compression. It would only take a slight imbalance of a few of the highest energy photons being used up to form electron/positron pairs to start a cascade. Once the gravitational collapse starts, enormous amounts of potential energy are converted to kinetic. Heating the layer of the star in the process, and so implosion turns to explosion. Depending on the size of the star this could just eject the outer layers or if the collapse proceeds further triggering fusion of heavier elements and you have a huge supernovae.

See: wikipedia – Pair instability supernova

I wonder what Eric’s take on the process is, since his cosmology posits entirely different processes — which seem to be on trial in nano-miniature with FF!

[mchargue]

So here’s some of the relevant FF hypothesis re the major heat generation cycle, from the patent:

The higher atomic charge, Z, of B11 greatly increases the x-ray emission rate, which is proportional to Z.sup.2 making it difficult to achieve ignition, e.g., the point at which the thermonuclear power exceeds the x-ray emission. The present invention overcomes these difficulties using a detailed quantitative theory of the plasma focus, described below, and the high magnetic field effect (HMFE). This effect, first pointed out by McNally, involves the reduction of energy transfer from the ions to the electrons in the presence of a strong magnetic field. This in turn reduces the electron temperature and thus the bremsstrahlung emission.

It sounds as if the energy transfer between electrons and ions is being impeded by the magnetic field. (and that is, apparently, a good thing) In an earlier post I made, I linked to an article that described the same mechanism w.r.t shielding a spacecraft from the ‘solar wind’. (a plasma) The article describes the disparate effect that a magnetic field has on electrons, and (their formerly associated) ions.

For spacecraft engineers, this was an unexpected phenomenon, but it seems in line with the idea that a magnetic field can lessen the heat transfer to electrons, and decrease the bremsstrahlung radiative losses.

https://focusfusion.org/index.php/forums/viewthread/576/

What say, elders?

[jamesr]

The strong magnetic field effect you refer to has nothing to do with the spacecraft problem. This effect only becomes important in very strong fields, in many orders of magnitude stronger than you have in the solar wind out where we are, they are typically measured in nT = 10^-14Gauss, in FF we have fields of 1^9 Gauss, ie 23 orders of magnitude higher.

[mchargue]

jamesr wrote: The strong magnetic field effect you refer to has nothing to do with the spacecraft problem. This effect only becomes important in very strong fields, in many orders of magnitude stronger than you have in the solar wind out where we are, they are typically measured in nT = 10^-14Gauss, in FF we have fields of 1^9 Gauss, ie 23 orders of magnitude higher.

The point of the article seems to be that a relatively weak magnetic field was responsible for blocking the solar wind on the moon, due to magnetic fields ‘frozen’ into ferrous deposits. It also talked about how a similarly weak magnetic field was used in an experiment to qualify the effect, and how the result of the experiment led some scientists to believe that a magnetic shield was back on the table for manned spaceflight.

I drew attention to the article because it seems to catalog an affect that might help explain why electron heating was minimized in the presence of a magnetic field.

[Aeronaut]

My understanding is that we’re validating McNally’s 1975 observation that bremstrahlung can be reduced by raising field strength, which has a lot to do with why high input currents are critical to reaching unity. This was mentioned in the GoogleTalks and in the patent, if I remember correctly. At this point it’s a theory which seems to be proving out experimentally, but I may be wrong on that- the relative motion of ions and electrons are beyond my direct understanding of the process.

[Author]

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