chrismb wrote:D Tibbets wrote:
Just to add some more confusion to confusing numbers-
CB, you quoted output for WB6 of 650 micro J for the pulse. Do you mean 650 micro watts? That number would be close to the ~ 1 billion fusion per second =~ few hundred micro watts which were the reported results for WB6. In any case the new numbers would allow the expermental results to be well within the limits allowed by your predictions.
Dan Tibbets
No. I mean 650uJ per pulse. The prediction for 2.5E16 ions each undergoing a fusion every 7000s is 3.5E12 (3.5 trillion) reactions per second. If the rate of reactions is some billion/s, then either the time-to-fusion is even more than 7000s or the total number of ions participating is less than 2.5E16, or some mix thereof. Remember I was being wholly generous with my numbers to show that my estimate for the residence time for an ion to undergo fusion was 7000s even whilst being overly optimistic. You should expect my generosity of figures to end up with a higher figure than measured experimentally.
I would suggest the figures are probably more like time-to-fusion = 14000s (because I was giving the highest experimental measures for cross-section, experimental measures which differ by ~100% at these low fusing energies) and around 1E14 for the total ion participation as only some 1% of the electrical discharge is likely to actually get ions moving on fusible trajectories. Then the numbers fit.
I hope you see how bad that comes out - only a thousandth of the electrical energy put in actually gets ions moving, and then they have to reciprocate around for 4 hours before a fusion event. You then get reaction rates as seen, in the billions per second. Maybe it gives a hint as to why I think fast neutrals into the chamber wall is a strong contender for a goodly fraction of the overall reaction rate.
OK, I figured my watts- joules argument was foolish, but it did serve to reenforce my understanding.
Some questions-
The 10,000 ion reciprications to a significant chance for a fusion event has been tossed around. But, what is significant- 99% chance, or 50%, or 1%, or 0.01%?. A 1% chance would be equivbalent to ~ 1 million reciprications for a very high probability of fusion (assuming a linier relationship). I assume your ~ 2.5 billion reciprications is the mean (50%) chance, so for a 1% chance 50 million reciprications would be needed (?).
Where does your 1/1000th efficiency of induced ion energies come from. Is it based on thermal tail in Tokamak type Maxwellian plasmas? I'm guessing that so long as the electron current is high enough to maintain the potential well, almost all ions in the Polywell reach the kinetic energy of the potential well. That is one of the claimed advantages of the Polywell over Maxwellian systems.
There is a difference between energy lost and ions lost. If an ion is lost near the top of it's potential well, the energy loss may be trivial. A thousand low energy ions may be lost, but the energy loss may add up to that in only one high energy ion. What happens to the low energy ion once it exits the magrid is confusing. Wouldn't it be accelerated away from the magrid, regaining it's kinetic energy? If this is irrelavent, then the numbers of low energy ions escaping is only important in regards to how fast you can pump them out of the system. I'm assuming the positively charged magrid is 'neutralized' by the nearly as strong negative electron charge inside the magrid so that the escaped ions do not pick up too much energy while outside the magrid.
Again, I understand that neutrals will be relatively rare inside the magrid so beam- neutral fusion collisions will be insignificant, and there are no (minimal) surfaces exposed inside the magrid so beam - target fusions will also be insignificant (as opposed to gridded fusors in which the deuterium loaded wires can serve as a target). So, where in the Polywell can beam -neutral or beam - target fusions contribute to the total?
Comparing the Polywell against gridded fusors: If the ions can recripricate 100,000 times before escaping and hitting something compared to a gridded fusor's 100 reciprication life time (in a very good fusor) then there is a 1000 fold advantage. In a fusor the ion loses most of it's energy, which has to be replaced in a newly ionized ion harvested from the background neutrals. In the polywell, assume only 1% of the energy is lost. That is another 100 fold advantage. Assumeing the Polywell can have a 1000 fold advantage in the density it can maintain in the reaction space (this does not concider convergance/ focusing which might effectively increase this density even more). This adds up to a 100,000,000 fold advantage for the Polywell. This is nearing the area of breakeven. Then, add the claimed advantages of monoenergetic ion energies (higher percentage of ions at the desired kinetic energy compared to the fusors where the ion velocities ar more diffuse (and lower average) due to dominate neutral and structure collisions ), confluence, possibly higher reciprication numbers/ density from even higher Wiffleball traping factors. At least from a hand waving perspective, doesn't this support arguments that the Polywell can exceed breakeven once certain size and magnetic conditions are met?
Bremsstrulung , if controlable as claimed, and other losses would not preclude breakeven, only influence the size and magnetic strength needed.
Dan Tibbets
To error is human... and I'm very human.