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  • #632
    Avatarslane
    Member

    Sunspots and stable nuclear fusion reactors
    The big problems of nuclear fusion research are:
    Nobody has seen a stable nuclear fusion reactor, we do not know what a stable nuclear reactor looks alike; we even have not a concept about stable nuclear fusion reactors.
    It is obvious that the sun is the only place can we find a stable nuclear fusion reactor.
    In fact, sunspots are one kind of standard stable nuclear fusion reactors.
    But, it is very difficult for us to understand that sunspots are stable nuclear fusion reactors.

    Then, how can we know that sunspots are stable nuclear fusion reactors?
    Every sunspot has a magnetic field. The magnetic field of a circular sunspot is similar to the magnetic field at the end of a long solenoid.
    Some astronomers such as Hale and Cowling want to use circular electric currents to simulate the magnetic fields of the sunspots.
    The circular electric currents are very large (1,000,000,000,000 Amperes for middle size circular sunspots), if we use a long solenoid to simulate the magnetic field of a circular sunspot.
    In nuclear fusion experiments such as Z-pinch experiments, hollow cylindrical plasmas (a long solenoid) with large circular electric currents will pinch and form high temperature high density hollow cylindrical plasmas, and nuclear fusion reactions will happen in these plasmas.
    So, strong stable magnetic fields of the sunspots just mean that there are stable nuclear fusion reactions in the sunspots.

    But there is a problem, who produce the large circular electric currents of the long solenoids of the sunspots?
    Astronomers think that sunspots are magnetic flux tubes, because nobody knows how to produce these large circular electric currents of long solenoids.
    In high temperature plasmas, large circular electric currents just mean that large number of electrons, protons and ions move circularly in different direction or in same direction with different speed.
    According to Newton’s three laws of motion (notice: Do not use Euler equation and Navier-Stokes equation of fluid mechanics), we need a centripetal force to drive the electrons, protons and ions move circularly.
    But there are problems:
    There are different kinds of centripetal forces, so what kind of the centripetal force drives these electrons, protons and ions of plasmas move circularly? Can this centripetal force describe all the plasmas motions of the sunspots (include Evershed flow)? Who produce this centripetal force?

    #4387
    Avatarslane
    Member

    We cannot get an answer just by studying sunspots, we must study other phenomena.
    Sunspots must be similar to atomic bombs, hydrogen bombs and hurricanes, if sunspots are stable nuclear fusion reactors, why? Because all of them release huge amount of heats continuously or in pulse manner, they are heats phenomena.
    Then, what are similarity and differences among atomic bombs, hydrogen bombs, hurricanes and sunspots?
    (1) Eyes
    The umbrae of the sunspots are just the eyes of the sunspots, like the eyes of hurricanes.
    (2) Eyewalls and magnetic fields
    The magnetic fields of circular sunspots can be simulated by long solenoids with large circular electric currents. These long solenoids are just eyewalls of the sunspots, like eyewalls of the hurricanes. There are heavy rains in the eyewalls of the hurricanes; but there are large circular electric currents and nuclear fusion reactions in the eyewalls of the sunspots.
    (3) Evershed flow
    Atomic bombs, hydrogen bombs, hurricanes and sunspots all have Evershed kind of outflows. But velocity of the Evershed flow of the sunspot is very large (1-9km/s).
    (4) Low temperature
    The temperatures of the sunspots and some mushroom clouds of hydrogen bombs are lower than that of their surrounding atmosphere.
    (5) Latitude distribution and periodical cycles.
    Hurricanes are similar to sunspots in latitude distribution and periodical variations of numbers.
    (6) Energy
    Atomic bombs, hydrogen bombs, hurricanes and sunspots all are heat phenomena.

    Conclusion:
    Some astronomers such as John Herschel and Hale think that sunspots are cyclone vortices of the sun.
    In fact, sunspots are just hurricanes of the sun, and these hurricanes have large circular electric currents and nuclear fusion reactions in their eyewalls.
    So sunspots are one kind of standard stable nuclear fusion reactors.
    The complex structures and motions of atomic bombs, hydrogen bombs, hurricanes and sunspots are caused by heats, so heats can produce some kinds of forces directly (Notice: Do not use Euler equation and Navier-Stokes equation of fluid mechanics). Certainly, electromagnetic forces play a role in eyewalls of the sunspots.
    But there is a problem: how to describe atomic bombs, hydrogen bombs, hurricanes and sunspots mathematically?

    #4388
    BreakableBreakable
    Keymaster

    Somebody got cosmology wrong again.
    Here is a quote from the infamous internet information source:
    “The core is the only location in the Sun that produces an appreciable amount of heat via fusion: the rest of the star is heated by energy that is transferred outward from the core”
    http://en.wikipedia.org/wiki/Sun

    #4435
    Avatarslane
    Member

    Breakable wrote: Somebody got cosmology wrong again.
    Here is a quote from the infamous internet information source:
    “The core is the only location in the Sun that produces an appreciable amount of heat via fusion: the rest of the star is heated by energy that is transferred outward from the core”
    http://en.wikipedia.org/wiki/Sun

    I certainly know it very well.
    Astronomers think that the sun can maintain stable nuclear fusion reactions in its inner core just by a centripetal force (gravity), it is a good idea, but it cannot be verified by experiments, because nobody can go in inside of the sun. I must emphasis that physics is an experimental science.
    Fusion scientists think that they can achieve stable nuclear fusion reactions just by electromagnetic forces, but they have not succeeded.
    We do not know that heats can produce forces directly.
    Sunspots kind stable nuclear fusion reactors are governed by a centripetal force and electromagnetic forces.

    #4436
    Avatarjamesr
    Member

    slane wrote:

    Somebody got cosmology wrong again.
    Here is a quote from the infamous internet information source:
    “The core is the only location in the Sun that produces an appreciable amount of heat via fusion: the rest of the star is heated by energy that is transferred outward from the core”
    http://en.wikipedia.org/wiki/Sun

    I certainly know it very well.
    Astronomers think that the sun can maintain stable nuclear fusion reactions in its inner core just by a centripetal force (gravity), it is a good idea, but it cannot be verified by experiments, because nobody can go in inside of the sun. I must emphasis that physics is an experimental science.
    Fusion scientists think that they can achieve stable nuclear fusion reactions just by electromagnetic forces, but they have not succeeded.
    We do not know that heats can produce forces directly.
    Sunspots kind stable nuclear fusion reactors are governed by a centripetal force and electromagnetic forces.

    Fusion in stars is incredibly inefficient & slow, hence why they last so long. The temperature in the core of only 10million degrees is only just enough to get the hydrogen to fuse. Further out the temperature drops rapidly till at the surface it is only 5400C. Sunspots are dark because they are upto 1000 degrees cooler. There is no way any fusion can occur at these cold temperatures and low density.

    In larger stars where the temperature & pressure is higher you can get other reactions such as the CNO cycle which make large stars burn much faster, hotter & brighter. Although there are certainly still large gaps in the knowledge of the internal workings of stars. The observations of millions of stars and their spectra, backed up by fusion probability cross section measurements on earth give us pretty good confidence that the fusion process in the core is the right model.

    To get fusion on earth at any appriciable rate you need to satisfy the Lawson criteria. That is you need the product of temperature, particle density and confinement time to be above a critical value. Magnetic fields are useful in obtaining the confinement but if you don’t have the temperature to go with it nothing will happen.

    For D-T reactions, which are by far the easiest, you need around 100million degrees (10 times hotter than the core of the sun) and for pB11 we will need an order of magnitude higher again. There are no shortcuts, or cunning ways to make it easier. To obtain breakeven (ie Lawson criteria) if you reduce one factor like temperature you need to make up for it with the others, eg by increasing the density.

    For those that want to get into the hard core physics, these are good introduction: Nuclear Fusion Reactions and Plasma Physics. They may look a little scary but just skip over the equations if you just want an overview.

    #4437
    Avatardash
    Member

    Speaking of magnetic confinement, recently I bought an old copy of Physics Volume 2 by Halliday + Resnick to review physics which I haven’t really used since college.

    I had remembered a proof that the magnetic field is just a manifestation of the electric field when special relativity is taken into account. It explained why two wires near each other carrying current in the same direction are drawn to each other. The moving electrons in each wire, when looking at the other, see stationary moving electrons in the other wire, but from their point of view the positive ions in the metal conductor are moving in the opposite direction. As such there is a lorenz contraction on the positive ion lattice, but not on the negatives. There being this contraction, there are more positive ions per unit length than negative electrons, so there is a net positive charge. So the electron is attracted to the other wire.

    The math worked out such that it varied only on the current — which is number of electrons times velocity. So the speed of the electrons cancelled out. So I thought it was cool, there not being this magnetic field at all, just the single electric field. I couldn’t find that derivation in the H&R;book. So maybe it was a different book.

    My actual point in commenting was this: I had had the feeling that in a magnetic field an electron moving across it would move in a circle of constant radius, regardless of velocity. My understanding was that the forces on the electron are proportional to its velocity, so that it would move in a fixed circle depending only on the strength of the magnetic field.

    What I discovered in the H&R;physics book is that the electron would actually complete a circle in constant time. So the radius of the circle would go up linearly with velocity. Slow electrons, small radius. Fast electrons, bigger radius.

    So that makes me think the standard torus tokomak fusion approach where big magnetic fields confine a plasma in a donut is hopeless, utterly utterly hopeless.. Because the ions in the plasma, naturally having a distribution of velocities, would be dispursed by any magnetic field. So the goal must be to have a stream of ions at exactly the same temperature all moving along in lockstep. But this isn’t what heat is. Heat is randomized movement. A stream of ions moving all along at exactly the same temperature would be matter at absolute zero temperature moving along.

    As such to counter the fellow who dismissed Bussard’s spherically symmetric magnetic field (polywell fusion) out of hand, I can dismess Tokamak fusion out of hand also! Yet that approach gets all the billions of research dollars. Go figure.

    -Dave

    #4438
    Avatardash
    Member

    Speaking of density of energy production, there is a table in Big Bang Never Happened where he shows that living organisms consume far more energy per unit volume of space than a star. And animals are just doing chemical activity, a million times less dense than fission, which is itself less energetic than fusion.

    I couldn’t grasp this concept. Lfe is higher energy density than the sun? Seems ridiculous.

    I think the energy density release of the sun averaged to something like 100 watts per cubic meter. That’s nothing! But then I realized the sun is really big. I imagined a 3d lattice of 100 watt bulbs stretching thousands of miles in every direction. The sun is a million miles across. You’ve got low density energy release coming out of a huge volume. The overall energy release is pretty big then.

    A fellow named Alexander Franklin Mayer came up with some alternative theories of the underlying physics of stuff. One thing he asserted was that the energy of particles that one wants to fuse has to be just exactly right for the particles to fuse and release energy. And his theory predicted the level of energy was very precise, and possibly different from standard theories. As such he said there might be a possibility of initiating fusion very easily, if you can just get the particle energy just right in collisions.

    Bussard makes this point. In a plasma of a specific temperature there is a distribution of velocities. His polywell fusion approach depended on ions of random temperatures being confined in the center by electric charge, so the ions are bouncing in and out for a certain minimum period of time. By that time they’ll have fused.

    And I think there are these things called “fusors” that maybe the guy who invented TV (Farnsworth) was using. Like an electron gun in a CRT. Accelerate ions to just the right velocity at a target and they’ll fuse. Seems straightforward. Set the voltage just right and stream ions and you’ll get fusion. But I guess the problem is break even and getting rid of the waste heat. Your target would need to be chilled to absolute zero I guess so its heat velocity would be eliminated.

    Sorry I’m just rambling.

    #4439
    Avatardash
    Member

    I just had an idea in the shower, maybe this could be a workable approach?

    Take a target of fuel and cool it to very low temperature so its thermal velocity is low. Keep it cold.

    Then direct a stream of fuel ions of precise velocity at the target in a vaccum. Some will fuse, releasing heat and X rays.

    The heat is waste, it heats up your target and must be eliminated. However the X-ray is your energy you capture, using Eric’s metal foil concentric spheres approach to get an electric current directly. This powers the cooling and ion gun and the pumps needed to recycle the gas that doesn’t fuse.

    The whole thing is very stable and completely controllable. Nothing to wear out.

    -Dave

    #4440
    Avatarjamesr
    Member

    dash wrote: I just had an idea in the shower, maybe this could be a workable approach?

    Take a target of fuel and cool it to very low temperature so its thermal velocity is low. Keep it cold.

    Then direct a stream of fuel ions of precise velocity at the target in a vacuum. Some will fuse, releasing heat and X rays.

    The heat is waste, it heats up your target and must be eliminated. However the X-ray is your energy you capture, using Eric’s metal foil concentric spheres approach to get an electric current directly. This powers the cooling and ion gun and the pumps needed to recycle the gas that doesn’t fuse.

    The whole thing is very stable and completely controllable. Nothing to wear out.

    -Dave

    Why bother cooling it? it’s not as if you need the collision speed to be an exact value so the sum of beam plus target adds up to a specific number. You want everything as hot as possible so the chance of the collision velocity of two fuel nuclei will be high enough to overcome the coulomb repulsion. If the collision is head on then each only needs to be going half the speed.

    The energy required to accelerate ions in a beam will always be many orders of magnitude more than you can get out by having that ion release energy by undergoing fusion.

    Accelerator experiments under carefully controlled conditions, like you describe, are useful to determine the precise collision cross sections (reaction probabilities), but useless as a way of getting energy out.

    #4441
    Avatardash
    Member

    jamesr wrote: Accelerator experiments under carefully controlled conditions, like you describe, are useful to determine the precise collision cross sections (reaction probabilities), but useless as a way of getting energy out.

    I’m not necessarily convinced of this. First off, you want the target cold because you want to eliminate the thermal heat velocity noise. Maybe there is an exact energy the ions need to fuse.

    Now as regards energy coming out, you’d charge up the target to a high or low voltage, whatever is correct to get the right speed ions hitting it. When an ion hits and fuses, does it change the net charge on the target? Maybe the charge stays the same.

    Keeping it all cool instead of a general hot plasma seems easier to control. Hot plasma is difficult to contain, as everyone knows.

    Just tossing out ideas. Thanks for your response.

    -Dave

    #4442
    Avatarjamesr
    Member

    dash wrote:

    Accelerator experiments under carefully controlled conditions, like you describe, are useful to determine the precise collision cross sections (reaction probabilities), but useless as a way of getting energy out.

    I’m not necessarily convinced of this. First off, you want the target cold because you want to eliminate the thermal heat velocity noise. Maybe there is an exact energy the ions need to fuse.

    Now as regards energy coming out, you’d charge up the target to a high or low voltage, whatever is correct to get the right speed ions hitting it. When an ion hits and fuses, does it change the net charge on the target? Maybe the charge stays the same.

    Keeping it all cool instead of a general hot plasma seems easier to control. Hot plasma is difficult to contain, as everyone knows.

    Just tossing out ideas. Thanks for your response.

    -Dave

    It’s good to toss ideas out there, but in this case its not going to work.

    An accelerator of this energy would typically be only a few percent efficient at ionizing and accelerating the ions (this efficiency drops rapidly as the beam energy goes up). Even then, if an ion beam hit a solid target, the ions would interact (via coulomb force) with many atoms at once, leaving an ionized trail of atoms in their wake. Gradually loosing their energy and heating up the target material. The chance of hitting a nucleus head on and so getting close enough to fuse is tiny, so most will loose their energy and thermalise with the surroundings after a few dozen close-ish collisions.

    Only a proportion of the fusion energy comes out as X-rays the bulk will be the kinetic energy of the Helium nuclei. These will come out at random angles – not related to the beam direction and quickly dissipate their energy in the target material as heat. If there were sufficient reactions to produce a meaningful amount of energy the target would vapourise and become a plasma anyway.

    There is indeed some preferred energies due to resonances (excited states) in the resulting transient nucleus. There is a small spike in the absorption cross section at around 148keV which could be critical in igniting pB11 fusion plasmas, but the main broad peak is over 500keV. The difference between having a target at room temperature (300K = 0.025eV) and cooled to say 3K is insignificant compared to the width of the resonance peak which is around 10keV.

    Nevins and Swain 2000 is a recent analysis of the pB11 reaction probabilites.

    The reaction rate for thermal plasmas is a combination of the reaction cross section for each speed, the maxwell-boltzmann thermal distribution, and the losses due to radiation. This masks out the spike of the resonance, but it adds a significant contribution at low temperatures.

    #4443
    Avatarslane
    Member

    jamesr wrote:

    Somebody got cosmology wrong again.
    Here is a quote from the infamous internet information source:
    “The core is the only location in the Sun that produces an appreciable amount of heat via fusion: the rest of the star is heated by energy that is transferred outward from the core”
    http://en.wikipedia.org/wiki/Sun

    I certainly know it very well.
    Astronomers think that the sun can maintain stable nuclear fusion reactions in its inner core just by a centripetal force (gravity), it is a good idea, but it cannot be verified by experiments, because nobody can go in inside of the sun. I must emphasis that physics is an experimental science.
    Fusion scientists think that they can achieve stable nuclear fusion reactions just by electromagnetic forces, but they have not succeeded.
    We do not know that heats can produce forces directly.
    Sunspots kind stable nuclear fusion reactors are governed by a centripetal force and electromagnetic forces.

    Fusion in stars is incredibly inefficient & slow, hence why they last so long. The temperature in the core of only 10million degrees is only just enough to get the hydrogen to fuse. Further out the temperature drops rapidly till at the surface it is only 5400C. Sunspots are dark because they are upto 1000 degrees cooler. There is no way any fusion can occur at these cold temperatures and low density.

    In larger stars where the temperature & pressure is higher you can get other reactions such as the CNO cycle which make large stars burn much faster, hotter & brighter. Although there are certainly still large gaps in the knowledge of the internal workings of stars. The observations of millions of stars and their spectra, backed up by fusion probability cross section measurements on earth give us pretty good confidence that the fusion process in the core is the right model.

    To get fusion on earth at any appriciable rate you need to satisfy the Lawson criteria. That is you need the product of temperature, particle density and confinement time to be above a critical value. Magnetic fields are useful in obtaining the confinement but if you don’t have the temperature to go with it nothing will happen.

    For D-T reactions, which are by far the easiest, you need around 100million degrees (10 times hotter than the core of the sun) and for pB11 we will need an order of magnitude higher again. There are no shortcuts, or cunning ways to make it easier. To obtain breakeven (ie Lawson criteria) if you reduce one factor like temperature you need to make up for it with the others, eg by increasing the density.

    For those that want to get into the hard core physics, these are good introduction: Nuclear Fusion Reactions and Plasma Physics. They may look a little scary but just skip over the equations if you just want an overview.

    The eyewalls of sunspots have huge amounts of the circular electric currents (1,000,000,000,000 Amperes for middle size circular sunspots), so plasmas in eyewalls of sunspots are in pinch state, that is, in high temperature high density state, so stable nuclear fusion reactions can happen in eyewalls of sunspots.
    Why do you think that sunspots cannot have stable nuclear fusion reactions?

    #4444
    Avatarjamesr
    Member

    slane wrote:
    The eyewalls of sunspots have huge amounts of the circular electric currents (1,000,000,000,000 Amperes for middle size circular sunspots), so plasmas in eyewalls of sunspots are in pinch state, that is, in high temperature high density state, so stable nuclear fusion reactions can happen in eyewalls of sunspots.
    Why do you think that sunspots cannot have stable nuclear fusion reactions?

    The current is irrelavent. It is quite easy on the sun to get large nett flows of quasi-neutral material, and hence large currents. The sun is after all quite big. But unless the individual ions are moving fast enough (ie. are hot enough) to overcome the coulomb repulsion you will get no fusion.

    Now up in the corona is does for some reason get up to a million or two Kelvin, compared to the 4500K or so for a sunspot. so you could potentially have some fusion there – but even this is too cold to have any appriciable chance of fusion, never mind that it is so rareified that the chance of a collision of two ions is incredibly low.

    Going back to your hurricane metaphor – the wind at the eyewall is fairly slow, the damge is done further out on the leading edge. But nowhere in a hurricance is there enough energy in the air to make is spontaniously combust or even the water in it boil.

    James

    #4446
    Avatarslane
    Member

    jamesr wrote:

    The eyewalls of sunspots have huge amounts of the circular electric currents (1,000,000,000,000 Amperes for middle size circular sunspots), so plasmas in eyewalls of sunspots are in pinch state, that is, in high temperature high density state, so stable nuclear fusion reactions can happen in eyewalls of sunspots.
    Why do you think that sunspots cannot have stable nuclear fusion reactions?

    The current is irrelavent. It is quite easy on the sun to get large nett flows of quasi-neutral material, and hence large currents. The sun is after all quite big. But unless the individual ions are moving fast enough (ie. are hot enough) to overcome the coulomb repulsion you will get no fusion.

    Now up in the corona is does for some reason get up to a million or two Kelvin, compared to the 4500K or so for a sunspot. so you could potentially have some fusion there – but even this is too cold to have any appriciable chance of fusion, never mind that it is so rareified that the chance of a collision of two ions is incredibly low.

    Going back to your hurricane metaphor – the wind at the eyewall is fairly slow, the damge is done further out on the leading edge. But nowhere in a hurricance is there enough energy in the air to make is spontaniously combust or even the water in it boil.

    James

    The temperatures of umbrae of the sunspots are approximate 4,500k, why do you think that the temperatures of plasmas in eyewalls of sunspots are 4,500k? The temperatures of plasmas in eyewalls of sunspots are certainly above ten million Kelvin.
    The velocity of the Evershed flow of the sunspot is very large (1-9km/s).

    #4447
    Avatarjamesr
    Member

    slane wrote:
    The temperatures of umbrae of the sunspots are approximate 4,500k, why do you think that the temperatures of plasmas in eyewalls of sunspots are 4,500k? The temperatures of plasmas in eyewalls of sunspots are certainly above ten million Kelvin.
    The velocity of the Evershed flow of the sunspot is very large (1-9km/s).

    Where do you get that temperature from??
    The velocity from dopper shift of spectra lines is indeed of the order of a few km/s but this is the bulk flow of material, and nowhere near the speed te ions need to fuse.
    The average energy corresponding to 10million K is 862eV ( conversion factor 1eV = 11604K). a KE of 862eV corresponds to a velocity of 200km/s. However even at that temperature only the protons at the top end of the thermal speed distribution have a chance of fusing. A proton with kinetic energy of 10keV has a velocity of 1500km/s

    There no evidence I know of that the temperature at any point in or around sunspots gets this high. Indeed the spectral data gives it away a bit. At the temperatures required you cannot get spectra lines. The plasma would be fully ionised; the electrons & ions have way too much energy to recombine and give off a visible photon.

    In any case the particle denisty is way too low in the photosphere to have any meaningful fusion anyway.

    On a side note – do you realise how unlikely fusion with ordinary hydrogen is? the cross sections (reaction probabilities) are measured in barns (cm^-24)
    at 10keV the cross sections are as follows:
    for D-T = 2.7E-2 barns
    for D-D= 2.8E-4 barns
    p+B11 = 4.6E-17 barns
    p+p = 3.6E-26 barns

    at 100keV it gets a little better, esp for the pB11
    for D-T = 3.43 barns
    for D-D= 3.3E-2 barns
    p+B11 = 3E-4 barns
    p+p = 4.4E-25 barns

    ie the probablility of a ordinary hydrogen (p+p) reaction is over 20 orders of magnitude lower than D-T

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