Potential of alternative energy sources?

Thanks Billy,
The reason I asked is that I have been reading up a little on Bussard's idea and I find it... intreguing, shall we say. Well, we should know something in the next few months, as the Navy decided to honor the existing contract and restored the remaining funds. Several members of Bussard's team and a couple of physicists from LANL are trying to verify Bussard's wb6 results with an improved six coil device (the wb7). Be fun to see what they find out.

 

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Perhaps you can search for earlier version - I seem to remember some one long ago had 6 square coils on faces of a cube. As you may know two coils of same diameter one diameter separated with current flow in same direction is perhaps the best way to make magnetic field uniform at the central point. The field strength there is not as strong as at the center of each coil. Plasma avoid high field strength if the can, so this is a weak magnetic mirror containment cusp. It unfortunately has huge leak out path - the entire circumference of the mid plane.

Thus three pairs of them makes, if all have same current very uniform field* at the center of the cube which is pointing at 45 degrees from the x, y, & z axis. If you now make one pair have current reversed, then the net central field will move to point into another of the 8 quadrants.

As I recall, their idea was like our "wiggler idea" but they "swirled the field around" - we had much less wiggle, but a much deeper magnetic well. I think their approach (and Bussard's if it is the same old idea), will never have a deep enough well to contain the pressure of a plasma both dense enough and hot enough to be of interest as a thermo-nuclear device, but I could be wrong. I would be happy if you to describe Bussard's version, results others are trying to confirm ,
etc.
There really is not much possible that has not been considered and rejected long ago.
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* There may be some “stability advantages” to a very uniform field swirling around a plasma in that some of the many instabilities do grow more rapidly the greater the field gradients are, as I recall, but we had two Ph. D.s doing the math of instabilities, so I didn't ever bother to try to understand most of them.

 

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Yes, Helmholtz coils. That's the worst possible thing for a polywell, to my understanding. The article about the polywell in Wiki has this wrong, btw, which had me scatching my head for a while. From what I've read the idea is someting like this.

Identical coils are arranged as if centered flat on the faces of an even faced polyhedron.(tetrahedron, cube, dodecahedron,etc. So far they have used mostly cubes) They all have the same pole facing inward. Which is immaterial but for clarity let's say the field lines go in toward the center through the coils and return out from the center between adjacent coils. (In the general areas of the polyhedron edges and corners, if you follow.)

Electrons are then injected into the 'trap' thus formed. The magnetic field is strongest at the center of the coils and at the spaces between the coils so electrons will tend to helix along a field line mirroring between the coil face and edge/corner regions like charged particles in the earth field. This happens on both sides of the coils. (both inside and outside the imaginary polyhedron). So, an electron can then be trapped inside the polyhedron, be trapped outside, recycle inside and outside, leak to the outer faraday cage (vacuum chamber wall), leak to the magrid or neutralize an ion.

The faraday cage is usually grounded with the magrid (outer coil casings) at a positive voltage, so few leak to the the faraday cage. The magrid is "magnetically insulated" to minimize this loss. (the "last minute breakthrough" was about this, they had bad leakage when the coil casings were closer than several electron gyroradii apart.)

They found they could maintain a dynamic balance with more electrons inside the polyhedron the out, the 'trapping ratio'. The space charge distribution of electrons creats an electrostatic potential well in the center region of the machine. Neutral deuterium was injected just inside the magrid, where it is rapidly ionized and the nuclei oscillate back and forth through the 'well' with a high probability of a 'headon', so to speak.

In broad terms, the device operates as a Farnsworth-Hirsch fusor with a virtual cathode and a magnetically insulated anode. In terms of the losses that make a fusor hopeless it's a completely different animal. Or so they think. Their computer models say so and match the test results thus far, or so they say. I myself have no idea, but it is interesting physics, and a lot cheaper to do than ITER. It might even work.

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To Kevinalm:

Thanks - not sure I followed, but it sounds like their idea for a machine has coils with the plasma circulating around them. If that is true sure seems crazy to me as an approach to fusion power. Just suppose it did work, then 17MeV fusion neutrons are slamming into the coils. Even if that problem could be solved, with some protective shielding they would sputter what ever the shield is made of (as neutral atoms initially across field lines) into the fusion reaction region and almost immediately (microseconds) quench the plasma and fusion by their radiative loses.

Hope I have not understood their geometry - coils in side circulating plasma will not work.

 

17 MeV Neutrons are a product of D+T fusion, not p+B11, problem solved, although the x-ray emissions is likely to present a major cooling problem for the coils.

The plasma is not circulating its pull electrostatical to "the well", In theory only the fusion products will have enough kenetic energy to escape, and then the magnetic field has to defend the coils from them.

 

Billy,
The idea is that except for fusion products, the only thing that nears the coils should be electrons. The system as a whole has a net negative charge from the injected electrons. The function of the coils is to manipulate this negative space charge to create a voltage potential profile inside the imaginary polyhedron. Call R the distance from the center of the device to the polyhedron face (that the coil plane occupies). At r=R the voltage is positive on the order of magnitude of the ultimate desired well depth. At r somewhat less than R the voltage goes to zero (ground) due to the trapped electron distribution. As r goes to zero, the voltage goes negative ultimately reaching that nescessary for fusion. (something like 10-15kv for D-D or D-T and 150kv or so for p-B11).

A neutral fuel atom injected just inside R is rapidly ionized, with the nucleus accelerated inward down the potential well. It then oscillates up and down the well. The maximum heigths reached being somewhat less than R. The fuel nuclei never reach the coils, or due so with very little velocity, and the coil casings are positively charged anyway.

I don't know if it will work, but it is an interesting concept.

 

Thanks again Kevinalm - I am beginning to get Bussard's idea. There seem to be three obvious concerns:

(1) As I understand it, some electrons are leaking out of the many cusps between the coils, but their loss may not be too bad as they can return along field line passing thru the coil centers. Most will just mirror back and forth inside along field lines as charged particles do in the Earth's ionosphere.
Unlike the ionospheric electrons which are following field lines with a radius of curvature greater than the Earth's radius (short segment of as 1000 meters are essentially straight) these Bussard elections will have high energy (needed to make the deep negative well) and a radius of curvature of a few meters. Now I am too lazy to see how cyclotron radiation scales with energy and radius of curvature, but seems to me that there is a good chance that electron with 150Kev (for the p/B reaction) whipping around the coils (or even just "mirroring" inside the interior between pairs of cusps will cool the system via cyclotron radiation. Wonder if they considered this?

(2) The multiple (fully probably) ionized boron B+++++ will fall down the well ok and climb up the other side, turn around and fall back down again.
The good part of this is they will be coming from all directions but not be entirely thermal in the center area where all the most energetic collisions can occur (Much better that trying to run a fusion reaction of less than 1% of them that happen to be in high energy tail of the Maxwellian distribution of a thermal plasma.)
The bad part of this is that they will be highly (or fully ionized) at the outer edges of the plasma with essentially zero energy as they turn around and be surround by electrons. Some of these electrons will be too fast for the B+++++ ions to capture. These fast electrons will have their trajectories bent by the 5 positive charges much more than when "scooting" by a single charge proton. I.e. this acceleration, 5 times greater will produce radiation at least 5 times greater. I think this alone will exceed the energy the reaction produces as even when only D & T are in the plasma and the energy is coming out in a neutral particle, there is significant energy loss via this unavoidable radiation.* (Not to mention the accumulating damage to the coils and especially the insulation between them.)
The slower electrons passing near an quasi stationary boron ion will just recombine with it radiating X-rays of various energies depending upon which level they drop into.

But captured or accelerated electrons are not the only source of radiative cooling. Few of the P on B collisions will be so well aligned (head-on) making fusion compare to 100s of times more strong collisions that that just scatter and again the B+++++ should make that radiation power at least 5 times greater. Of course if B and P (the proton) are in equal concentration (you want that for highest rate of reaction) then there are and even more B on B radiative scattering as their head-on collision ALL bounce 180 degrees as they lack the energy to fuse (approach within the strong force range) If he does get some fusion, then each produces three energetic alphas to bang into boron and protons and make huge accelerations of those charged particles - more radiation losses (but I doubt we need worry about this

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(3) It will be impossible to keep the plasma free of the "out gassing" molecules (especially in the intense X-ray and flux hitting the wall of vacuum chamber as electrons are captured into the inner atomic shell of B+++++ making it into a B++++ ion etc.) Once these atoms (typically Carbon, Oxygen and Nitrogen, perhaps a little Cl or F from the plastics of coil insulations) get in to the energetic plasma it will cool quickly by this high energy continuum radiation (Mostly X-rays but even some lower energy harsh UV -perhaps even some short wave length visible line as part of the recombination of the electron lowering the degree of ionization will cascade down the many high principle quantum numbers instead of be directly captured into a deep atomic shell of the B+++++ etc.

I am just guessing and drawing on old memory* but think that Bussard's machine will at best be an alternative source of radiation not energy. I.e. it will never get to the state of fully ionized plasma in a 150Kev deep well because of the high power radiation (Photons, not radioactivity) it will produce in the effort to get there.
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*As I recall in the old Princeton "stellarator" they were stopped by the radiation losses well before getting to even D/T reaction temperature by the fact that the vacuum systems was not good enough - too many multiple charged ions in the plasma. At Princeton, as I recall, they finally got these vacuum system impurity atoms radiation losses down by modifying the magnetic field so that the outer flux line went out into something called a "diverter" with liquid nitrogen cold traps to freeze out the unwanted ions that were radiating away all the energy as fast as they could put it in. (Effectively they "çaught" the atoms out gassing from the chamber walls as soon as they became ions - I.e. while still in the outer "skin" of the confining magnetic field and led them out into the "diverter's cold traps.)

Unbelievable (for me at least) is that Bussard wants 50% his plasma to be these multiple-charged radiating atoms!

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Thus, I predict it will, at best, be one expensive X-ray light bulb.

Put me down as "very skeptical". Has no one done these radiation calculations? To put it very crudely, but clearly, it seems to me he wants to fill a bucket, which as large hole in the bottom (the radiation), by pissing in it with a small steam of energy flow (the injected electrons).

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*Not only is the "unavoidable" radiation at least 5 times less, the fusion cross section is greater and the energy release per fusion is several times gfreater also - so in the DT reaction the unavoidable radiation is sustainable. I strongly doubt it is in The PB reaction as all three factors are stacked against it -by my crude estimate: 5x5x5 = or > 125 I.e. Bussard is at least 125 times worse off.

 

Their nothing wrong with being skeptical, the question is would you fund be willing th fund it if you could?

 

I would first fund a careful analysis of the radiation losses before I built hardware (Note I almost always like to test as the theoreticians can always find some way to earn their pay.)

Reminds me of the old university joke: The bean counters and Dean have called in the head of the physics department and tell him that his funding request (lots of dollars for new equipment) needs to be greatly reduced. As the discouraged Physics head is leaving the dean suggests: "Go talk to the head of the math department. - We cut their budget to. They requested paper, pencils and new waste baskets. We told them to be more careful and then they would not need the waste baskets."

 

Simulations are only as good as your knowledge of the experiment, and useless if you don't know all the inputs.

Building of small scale models seem to demonstrated feasibility, and the simulations based on the small scale seem to demonstrate feasibility, why not fund a larger scale test bed?

 

True you must be confident in your understanding of the effect you calculate (no simulations here required.)
For example, 50 years ago one could accurately predict the intensity of cyclotron radiation given the radius of curvature and the net unbalanced charge flows or current. First thing to do is to estimate the dominate radiative loss mechanism (probably more than the half dozen or so I discussed in the prior post) and ingore the minor ones.

Likewise the intensity of Bremstralum (radiation during collisions without capture of electrons, which is a separate mechanism producing X-ray or very harsh UV) is well known but one would need some model* of these collisions as Bussard's ions may not have a thermal distribution (the electrons surely will as we can calculate the time for any initial distribution to thermalize - electrons are very fast to do so. I suspect that the ions will also be essentially thermal in their distribution after 3 or 4 falls thru the well, but it will depend upon the ion density along their trajectory. (You will need that any way to estimate the fusion rate)
Ions, even only the proton do not come to the same temperature as the electrons have as quickly as they thermalize at their own different temperature, and may in Bussard's device always have a difference as the elections are constantly entering as a beam to disturbed LTE (local thermo-dynamic Equilibrium)

There will be some uncertainties in the calculations, probably less than a factor of two, if well done. If these calculations show that when fusion conditions* do exist that the radiative power loss is several hundred times greater (as I suspect) than the fusion power being produced, then the idea is silly.

It is a lot cheaper to calculate than to build. Have three different independent calculations made.
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*Density and temperature spatial distributions; or if no true ion temperature exists, then use the non-Maxwellian distribution to compute the fusion rate.

I suspect that the system has so much radiative losses that one could be very generous in the estimation of the fusion produced and still conclude that the loss rate exceeds the energy production rate.

For example, FALSELY assume that NONE of the energy the positive ions gain in falling down to potential well is lost before a P on B collision occurs (no B on B or P on P collisions). This would grossly over estimate the fusion power production, and grossly underestimate the radiative loss due to scattering of charged particles in the real B on B or P on P collisions that are assumed not to exist but make the calculation simple. All the various impact parameters would of course be retained - can't assume that every collision is head on and results in fusion, and ALL the P on B collision that occur on the way to the center before gaining the necessary energy to overcome the Coulomb barrier ONLY produce radiation. I.e. only an extremely small fraction of all collision will result in fusion, EVEN WITH THESE VERY GENEROUS FALSE ASSUMPTIONS. I.e. for impact parameters approximately equal to "nuclear touching" (use classical radii of B & P) separation between the P and B assume fusion occurs in 100% of the collisions and for all greater Impact parameters compute the radiative losses.

If even with these unrealistic assumptions there is still and order of magnitude greater radiative losses then there is no need to do the more difficult (but still "doable") computations.

To give a simple analogy: one dose not spend a lot of money building a bridge over a river on the hunch that the design is good, and hope that it will not fall down - one calculates and throws in a "safety margin." What we have in Bussard's case, is someone saying let’s build the bridge this way and I am saying let’s compute the strength of that design. If that computation shows that it cannot be self supporting, even if the weight of the steel were only 5% of the true weight, then do not spend the money on building the bridge.

I do not have proof that Bussard's design will have loss rate at least 20 times more than energy production rate but based on the 40+ year old results Princeton’s Stellarator EXPERIENCED** I think that is the case.

**Stellarator had excessive radiative loses with less than 0.1% concentration of multiple ionized contamination ions coming from the out gassing of the walls before the "diverters" were added (Bussard wants HALF of the ions to be B+++++ ) !!!

It will be at best a soft X-ray / harsh UV, light bulb, not a fusion device.


"Those who cannot remember history are condemned to repeat it." - Santa Anna, I think.

 

the experience of the past does not determine the future: "for centuries they tried to make heavy then air manned flight, and failed, therefor it can't be done, we will never have airplanes or helicopters, it can't be done all previous work show it."

Both Lenar and Bussard claim their result circumnavigated the problems of Bremstralum radiation and ion-electron collisions. And their reactor designs are significantly different from predecessor designs. Their calculations showed how. What is left to do but prove the calculations wrong or right?

 

There is no significant uncertainity in the calculation of each impacts (given the charges, their relative velocities and the impact parameter. Sort of like there is no significant uncertainity in the acceleration the sun is giving the Earth* - Once the acceleration is know for each and every possible collision in the distribution (which probably is very close to thermal, but that is separate problem to solve first) then Maxwell's EM equatins give the radiation.

You are confusing the perfomance of an entire system (airplane) with a summation of very well understood essentially BINARY EVENTS on an atomic scale.

We understand how much radiation each BINARY scattering of pair of charged particles will make. - just compute them all and add them up (I.e. get the averaging over the distribution). The only uncertainity is in the distribution, but this is the the same distribution as used to compute the fusion power.

For example, see how the lost rate vs fusion power rate compare, assuming a thermal distribution of the ions. Then assume another distribution and repeat the computations, etc. If no distribution exists for which the fusion power production rate equals the loss rate, then with 100% confidence you can conclude it is a waste of money to build it.

"Claimed"? Where is there published analysis? I have heard many claims that a $25 device added to my spark plugs will double my gas milage, but never seen that published in a pier-reviewed journal. If what they claim has analytical support (not just belief, hope and faith) where is it published?
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*In fact both are mathematically identical as both accelerations are the result of inverse square law forces.

 

If that was so then their results from physical experiments would be wrong, either how they collected the results is wrong, or their is a mechanism that your no assuming for correctly, for example they demonstrate non-thermal ion distributions occurring. Either way it warrants more study, more money.

 

As I guessed.* But note I suggested that the calcualtions be done for many different distributions, Even the extremely unrealistic and very favorable to Bussard one of assuming that the ions fall into the well without any loss of energy as the do so by P on P or B on B collisions until the P on B collision occurs. When the fusion rate is calcualted with that false assumption many more fusions will occur as they have the maxium possible energy when the P on B collision occurs. N ot only that this assumption ignroes all the radiation losses that would be produced during the P on P and B on B collisions.

I made no suggestion that ONLY a thermal ion distribution be assumed. I suggusted one of the assumed distribution be extremely and falsely favorable to Bussard.
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*Recall I guessed that AFTER 3 or 4 falls thru the well, that then the ions that have that many or more passes are with a thermal distribution.

I agree more money should be spent on the idea - for the calculations to see if it has any possiblities even giving unrealsiticly favorable assumption to the idea.

 

Those "extremely and falsely favorable" distributions seems to explain their experimental results so either its a fluke or its accurately favorable, not falsely.

 

I would need to see how the claimed results were obtained published - I am reminded of cold fusion, which did get some articles published in frist rate journals. Have they?

 

Go to their websites, don't load copies of their results. I remind you that cold fusion had to be proven bogus by third parties repeating the experiments.

 

And I remind you that I and 99+% of physics Ph.D.s were very convenced by our understanding of the difference between nuclear and chemical reactions to state that it was a bogus claim prior to any failure to confirm experiments.

Please give me link to location where Bassard's work is published, instead of only claimed.

 

Yes and the majority of physicist in nazi german believe the nuclear bomb was impossible, thankfully they were wrong. Face it a large percentage of science has come into being because of the discoveries of things not predicted, we cannot simply say "well we predict it will not work, therefore we should not try".

You do have a point, I've never seen Bassard's work either but Lenard's is available. Also bassard's work has been cacluated by others a feasible:
http://scitation.aip.org/getabs/ser...00007000011004547000001&idtype=cvips&gifs=yes