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Re: Dr. Park invites questions from the community

Posted: Sat Feb 06, 2016 8:19 am
by ltgbrown
hanelyp wrote:One BIG question: what uncertainties remain to be resolved?


This is exactly what Ladajo and I are talking about. As Dr. Park mentioned, they need to address the "remaining scientific concerns" and then move onto demo. So, what are those concerns? Why are they concerns? Is there one (hopefully only one!) that you are most concerned about? Why?

Another question might be what engineering challenges do you foresee for moving on to demo?

Then looking forward and assuming all this Polywell stuff works, just what power output to size ratio do you see as obtainable? Could it power a large plane? How about a train?

Very exciting!

One last (and probably the MOST important) question: When can I buy shares of EMC2? :D

Re: Dr. Park invites questions from the community

Posted: Mon Feb 08, 2016 9:28 pm
by hanelyp
Expanding on my idea in http://www.talk-polywell.org/bb/viewtopic.php?f=4&p=124254&sid=ff7cf17dac37a2adde461b51c54cb191#p124254, subtlety vs. brute force for electron injection.

Re: Dr. Park invites questions from the community

Posted: Tue Feb 09, 2016 10:21 pm
by JoeStrout
OK, thanks everyone for the brainstorming. I've fallen behind schedule now, and asked Dr. Park to give us a few more days to get our act together. So let's see if we can whittle this down to our top 10.

Here I've gathered all the questions I found, combined ones that were essentially the same, and attempted to group them into categories for easier consideration.

SCIENTIFIC QUESTIONS

1. What are your remaining scientific concerns and which one concerns you the most?

2. What are the prospects for operating Polywell in a steady-state vs. a pulsed mode? (And would the use of p-11B make steady-state operation easier or harder?)

3. What scaling laws do you expect (if it is not too early to ask that)?

4. What is the primary mechanism impacting electron injection efficiency, and how does this scale in projections to a viable machine?

5. The machine designed to achieve and demonstrate high Beta effects had wide separations between magnets. Does this reflect improved cusp confinement compared to WB6 and imply a need to keep ExB losses from becoming dominate? For that matter, without a deep potential well, are ion cusp losses dominating the picture over electron cusp losses in this machine, at least as higher Beta is reached?

6. How much did the internal magnetic field measuring coaxial cables limit achievable Beta?

7. Is there a reconciliation between this machines low Beta cusp confinement numbers and those claimed for WB6? WB6 was ~ 60 passes , while this machine was ~7 passes. Given that simple biconic mirror confinement was quoted as ~ 5-8 passes (in the older patent application), the numbers for this machine ('Mini B' as it has been called here) seem small. Is the increased magnet spacing distance combined with the overall smaller size (relative differences magnified) significant, despite the increased B field strengths?

8. The reported neutron counts for the relatively large reaction space in WB7 seem modest compared to simple amateur fusor reports with only modestly higher voltages, and this is ~ 3 orders of magnitude less than that claimed for WB6. Was deep potential wells obtained in WB7,and 8? You mention that deep potential wells were obtained in 1995, how about in WB7 and/ or 8?

9. The bridging nubs may have been a major source of sputtered plasma in WB6 with an unknown percentage of the greater than 40 Amps of high energy electron current hitting them. Was this found in WB7.0? Did the elimination of these nubs starve the machine of a plasma source?

10. What is your take on several mechanisms that have been proposed for application to the Polywell. These include edge annealing, effect of the potential well on Bremsstruhulung losses, effect of diluting the high Z fuel (He3 or B11) on Bremstruhlung losses versus fusion output, etc.


PROCESS/DEMO QUESTIONS

11. What is the target $30M machine, and why not just put the required hardware on WB-8 instead of a new machine?

12. What engineering challenges do you foresee for moving on to the demo?

13. Can results be obtained quicker than 3 years if expediting funds are obtained?


P-11B QUESTIONS

14. We hear the target fuel for the first reactor is D+T. Is that to play it safe? What are the prospects for D+D, Tritium catalyzed D+D or even He3 catalyzed D+D (with Tritium or He3 bred from fusing D+D)?

15. What is your best guess for the acheivable, time-averaged, usable power density for p-11B over time spans of, say, 10 minutes (ascent time to LEO)?

16. With p-11B, do you expect any significant gamma emissions?


"OTHER IDEAS" QUESTIONS

17. The Lockheed patent suggests that they are exploring dynamic compression effects by cyclically varying fields. Would "dynamic compression" (including perhaps LANL's POPS) be worth investigating for Polywell?

18. If highly positively charged magrid cans leads to loss of central dominate potential well in the corner cusps, can this be mitigated by moving the charge to a ribbon on the outer surface of the cans-effectively increasing the radius of the accelerating positive electrode by a few cm or more?

19. Bussard reported that the average speed of ~ 10 KeV injection energy electrons in WB6 was about 10 million cm/s. This presumably reflects the effects of a deep potential well, with the electrons spending a major portion of their lifetimes at significantly slower speeds. Without a deep potential well the average speed is significantly higher. This is significant for Bremsstruhlung radiation and also for confinement as measured by time, not so much for number of passes measure. Is this consideration reasonable?

20. Can a neutral beam of slow electrons matched with fast ions serve as both an efficient electron injection and cool ion injection source? This presupposes a positive charge on the magrid (outer surface only charge tolerable?) to accelerate the electrons while slowing the ions .This may serve to keep the beam more narrow than pure electron beams of the same current while also allowing for cold ion injection. The ions would give up most of their energy to the positive magrid (a direct conversion effect) and enter the machine at low voltage cool conditions. Further cooling inside the machines through radiation losses might keep them adequately trapped in the potential well. Better electron injection efficiency is hopefully achieved. This opens up other questions and compromises, but is this a possible solution?

21. Without sufficient positive charge on the magrid, recirculation is only possible by the electrons (and ions for that matter) looping around to another cusp. Is this possible to do with sufficient efficiency despite ExB and instability issues? Will an additional layer of external magnets be necessary? This seems to be the approach championed by Dr McGuire at Lockheed. Do you feel that electron recirculation is a needed feature for the Polywell, or can primary high Beta cusp confinement of electrons suffice?


FUNDING/BUSINESS QUESTIONS

22. Why did the Navy end its involvement?

23. When can I buy shares of EMC2? (Or more seriously: is there any way for ordinary people to invest in or contribute to the research?)

24. Have you considered starting a polywell indiegogo for funding?


So we need to eliminate over half of these. Or, if you prefer, bless fewer than half of them! Opinions please — no new questions, just support or argue against existing ones. We're looking for the 10 questions that Dr. Park is going to be uniquely able to answer, and whose answers are likely to provide the greatest value. (So for example, I'll argue against question 22 — he probably can't say anything substantial about it, and knowing the answer would be unlikely to help us much anyway.)

Have at it!

Re: Dr. Park invites questions from the community

Posted: Wed Feb 10, 2016 2:03 am
by ladajo
I vote to drop 12, 13, 15, 22, 23, 24

I think we should focus to scientific or technical questions. I will mull a but more and then vote for some keepers later.

Re: Dr. Park invites questions from the community

Posted: Wed Feb 10, 2016 2:31 am
by bennmann
I vote for 1-8, 11, 16

Re: Dr. Park invites questions from the community

Posted: Wed Feb 10, 2016 5:23 pm
by JoeStrout
Seems reasonable so far. Any other opinions?

Re: Dr. Park invites questions from the community

Posted: Wed Feb 10, 2016 7:51 pm
by ltgbrown
Looks good to me, although I would be interested in hearing what challenges lay ahead, scientifically (1) AND engineering wise (12), to having functional fusion reactors.

Re: Dr. Park invites questions from the community

Posted: Thu Feb 11, 2016 1:08 am
by D Tibbets
On question 19

19. Bussard reported that the average speed of ~ 10 KeV injection energy electrons in WB6 was about 10 million cm/s. This presumably reflects the effects of a deep potential well, with the electrons spending a major portion of their lifetimes at significantly slower speeds. Without a deep potential well the average speed is significantly higher. This is significant for Bremsstruhlung radiation and also for confinement as measured by time, not so much for number of passes measure. Is this consideration reasonable?


The potential well may need to be elliptical as mentioned in Bussard's GOOGLE talk. With a square potential well where the electrons are zipping around just inside the Wiffleball border there may not be much variation in electron speed.

Dan Tibbets

Re: Dr. Park invites questions from the community

Posted: Thu Feb 11, 2016 9:19 pm
by JoeStrout
OK then, unless somebody strenuously (and quickly!) objects, I think I'm going to send on questions 1-8, 11, and 12.

Question 13 is interesting but the answer is likely to be "probably not," and "as if we should have such a problem." 12, on the other hand, is more concrete and seems more likely to produce a meaty answer.

EDIT: Oops, you suggested 16, not 13. OK, that one's better, but something still has to go — and I too want to hear the answer to 12. So I suggest we let 16 go, unless somebody prefers to ditch something from 1-8.

Re: Dr. Park invites questions from the community

Posted: Fri Feb 12, 2016 3:10 am
by ladajo
I think that 11, 12, 13 can be rolled up into: What is the next proposed test machine going to look like, and what will be the biggest engineering challenge in its construction?

Then maybe that leaves space for another: What are your thoughts on the proposed test plan and regimes for this new machine?

Re: Dr. Park invites questions from the community

Posted: Fri Feb 12, 2016 3:54 am
by JoeStrout
I like it. That makes sense to me.

Going once... I'll send this off to Dr. Park in the morning if there are no further suggestions.

Re: Dr. Park invites questions from the community

Posted: Fri Feb 12, 2016 4:32 am
by mvanwink5
It does not cover why that size?

Re: Dr. Park invites questions from the community

Posted: Fri Feb 12, 2016 12:25 pm
by ladajo
Cost
:D

Re: Dr. Park invites questions from the community

Posted: Fri Feb 12, 2016 12:34 pm
by mvanwink5
Whatever.

Re: Dr. Park invites questions from the community

Posted: Fri Feb 12, 2016 1:22 pm
by ladajo
I think Joe can include that in the 11-13 roll-up.

If not, we may get lucky and Dr. Park answers on that on his own as part of his feedback.