FAQ: Fusion ash/byproducts -Energy- How much?

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
jst
Posts: 120
Joined: Mon Oct 07, 2002 4:34 pm
Real name:

Re: FAQ: Fusion ash/byproducts -Energy- How much?

Post by jst » Mon Feb 09, 2004 2:25 pm

Just to point out a few issues here;

1) A fusor, probably will never produce more than about 50KW of energy. The mircostar is extremely small, and I don't think you can get that much fuel in or energy out. I would love to see one of these produce 4MW, but that seems extremely unlikely given the size of the microstar.

2) At 50KW, a fusor would discharge something like 81megaCuries/sec! Some form of containment isn't an option... it is mandatory. That thing will deliver a lethal dose in much less than 1 second. At the experimental stage, we're looking at 6 feet of water or 20 feet of sand as a shielding medium in all directions ( gotta big swimming pool? )!

3) Current fusors are "by collision" devices; correct. In fact as Richard(?) said this is nothing but a low energy acclerator in the form of a sphere. The sphere increases the probability of collision, which would otherwise be very small, and difficult ( Uncertainty Principle here ).

4) Current fusors do not offer any "containment" capability; Only a partially true statement. Current fusors inject ions into a microstar. They contain and locate the microstar within a limited region of space ( just like a cylinder in a gas engine does ), and the associated plasma and fuel . However, it DOES NOT contain fusion byproducts, including any and all alpha, beta, gamma and neutron outputs ( in excess of the driver voltage of the fusor ) ... and this is precisely the source of fusor "inefficiencies". As there is no positive feedback into the process, because all input energy and all output energy is effectively lost, current fusors are at best laboratory curiosities suitable for lambasting the multibillion dollar efforts of "mainstream" fusion researchers.

Indeed, the analysis on this board which itemises why current fusors can never sustain fusion applies just as well to those multi-billion dollar projects with magnetic confinement, for exactly the same reasons... and we note that magnetic fields are nowhere near as strong as the blast coming from 45KEV fusors.


In short summary, my position is, that fusion can never be made to work unless there is a positive feedback mechanism in the fusion plasma region ( i.e. the microstar ). Since fusion energies are in the realm of minimum 4MEV up to 22MEV, any containment protocol must necessarily exceed 22MEV to keep both the microstar and its fusion products in the same locale.

The only known "containment" mechanism for neutrons is collission with another ( of any type ) more energetic particle. Therefore, a fusor must produce an ion shower of greater than 22MEV to stop (say ) 81megaCu/sec of neutron radiation. ( Perspective -- Remember, 1AMP is 10^18 electrons, and a MilliAmp is 10^15 electrons ). We have our work cut out for us.

Currently, the only technology anyone has that can produce MEV level ion showers is the CA - WFA based technologies that Larry has such a strangle hold on. Larry's recent proposal to inject a strong electron beam into a fusor microstar to produce MEV range protons is spectacular in its simplicity. If we can cascade such a device into a high ( 100 MEV ) energy beam ( preferably of electrons ) then something approaching full contaiment might be achieved.

While I don't expect 100% efficiency ( and therfore 100% containment ) the ability to extract 1/3 of a microstars energy ( i.e. 16KW ) would not be an insignificant result. But it would never produce megawatt or gigawatt power levels.

User avatar
Adam Szendrey
Posts: 1333
Joined: Fri Mar 29, 2002 10:36 pm
Real name: Adam Szendrey
Location: Budapest, Hungary

Re: FAQ: Fusion ash/byproducts -Energy- How much?

Post by Adam Szendrey » Mon Feb 09, 2004 4:14 pm

Joe,

The size of the microstar is not necceseraly a limiting factor. Remember that at higher energies a more powerfull containment field will result in the same size, BUT ofcourse energy (plasma) density increases.

As for cascading CA. I don't know exactly what do you mean by that but remember that a 4 MeV (these numbers are used as simple examples) proton can accelerate an electron up to 2 keV, and not to several MeV (electrons are about 2000 times lighter).
So if you produce a 4 MeV proton beam and ram it into an electron plasma it will result in a 2 keV electron beam (though i'm not sure that would work), or more like a neutral beam of 4 MeV protium atoms (i would guess that electrons recombine with protons as they match speed).
So i don't know how you want to cascade it.
But if the ion plasma is not a proton plasma , instead it's something heavier, say nitrogen plasma, than the resulting particles will have much higher energy.
Nitrogen has 7 protons and 7 neutrons. Thus it is 14*2000 times heavier (very crude approximation indeed) than a single electron.
Thus the result is a 56 MeV (!!) ion beam...Quite a meanie!
Sounds a bit irrealistic...a 56 MeV ion beam (or again rather a neutral beam, ofcourse it will only be neutral if ions have a long enough path to match speed) from a 2 keV electron beam?
A nitrogen nucleus is 14 times heavier than a single proton, but it is 7 times "more positive" too.
So i would guess that a nitrogen nucleus will require a path twice as long as a single proton does, to match speed with the electron that is hauling it.
Oh and ofcourse a nitrogen atom will need a lot more energy to be totally ionized!

Adam

jst
Posts: 120
Joined: Mon Oct 07, 2002 4:34 pm
Real name:

Re: FAQ: Fusion ash/byproducts -Energy- How much?

Post by jst » Mon Feb 09, 2004 5:44 pm

Good points. Never the less, the likelyhood that we'll be forming large microstars, capable of feeding that much fuel thru them does seem a bit remote at best from where we are now.

As for cascading, I agree with your analysis. Larry has conveniently paved the way, for some pretty basic tests. They would be;

1) Does it actually work as advertized? Does a 2kev electron beam actually punch out a 4MEV proton beam from a spherical microstar of probably 2KV? Would that be a 8MEV beam if dueterium ions are used? Test?

2) If the microstar is more like a filament, does that still stay at 4MEV, or does it escalate the longer the plasma path is?

3) Just to make sure, exactly what does happen if a proton is fired at an electron plasma microstar? Experimental evidence?

From my point of view, I see WFA as achieved by a particle being fired into a string plasma filled with standing waves. The CA effect in a fusor I see as one lobe of the standing wave. A 2000X amplification looks pretty promising in that light. But without experimentation this is all bluesky...

P.S.-- BTW, since CA is a conservation of momentum thing, just keep out of the beam and radiation should be close to background.

P.P.S. -- Speculaton... do you suppose that an asymetric current inside a fusor might cause 4MEV something to come out of the fusor in a specific direction? Could this be the source of anomalous radiation events? Bet you most people don't have the fusor instrumented at all points of the compass...

User avatar
Adam Szendrey
Posts: 1333
Joined: Fri Mar 29, 2002 10:36 pm
Real name: Adam Szendrey
Location: Budapest, Hungary

Re: FAQ: Fusion ash/byproducts -Energy- How much?

Post by Adam Szendrey » Mon Feb 09, 2004 7:10 pm

A couple more thoughts:

The electron beam approaching the ion plasma might be deflected/scattered by the inner negative grid.
This is another point for making an axial tubular grid arrangement, so both the gun and the grid's axis is on the same line (the grids would be open at both ends ofcourse, like a simple tube).
I have an idea for cascading that might or might not work.
The following arrangement should be imagined:
An electron gun a positive plasma (protons for eg.) and after that a negative plasma of a heavier element than a single proton (deuterium for eg.).
Now as the electorn beam accelerates the protons (given that the path is not long enough for recombination to occur) reach the negative plasma and haul the heavier neg. deuterium ions with them.
Some concerns: Since protons are "big" and they hit a negative plasma containing similarly big ions (bigger), collisions take place reducing efficiency, or resulting in total failure.
The protons "steal" the electrons from the negative deuterium ions and nothing else happens. Though 4 MeV particles might not recombine with relatively stationary particles...

IF this some way works the result "should" be a 8 MeV beam of deuterium ions, 4 MeV protons, and 2 keV electrons...Now there are some possibilities here....the extra electron from the deuterium ions (neg.) "jump over" on the protons, or the protons recombine with electrons from the original beam...or both.

It is much easier to accelerate positive deuterons with the original 2 keV electron beam to get a 8 MeV deuteron beam, but that does not contain a "secondary" ion beam of protons.

Adam

User avatar
Richard Hull
Moderator
Posts: 11611
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: FAQ: Fusion ash/byproducts - endoergic d+d rxns

Post by Richard Hull » Mon Feb 09, 2004 9:27 pm

The two other reactions are variants of the Oppenheimer-Phillips reaction! This reaction is unlikely below about 4-6 mev (terrible cross section). These reactions are sometimes referred to as "stripping reactions".

These reactions are ENDOERGIC! These are big energy LOSERS! You are literally ripping matter appart and DEFEATING the "nuclear" bonds. You are not fusing here, just tearing assunder.

At one time, on the old songs list, it was put forth by some rather un-informed naysayers against amateur fusion in a fusor that the neutrons observed from the fusor were the result of "stripping" and not fusion. Of course this put me on a quest to contact good and knowledgeable physicists. I posted on the results found via discussion and in the excellent book I reported on in the Books and refs forum, "Fast Neutron Physics".

The upshot is that no form of stripping reaction is even possible on a statistical basis until about 4 mev and becomes a bit more common after 6 mev. In a stripping reaction you are hitting with such force that you are just shearing the deuterons into component parts and not really doing any fusion at all!

Finally, it is stupid to suggest stripping as opposed to fusion at amateur energy levels! All we are ever capable of IS FUSION! This is based on simple cross sections at our voltages.

The threshold levels mentioned are those energies where these two latter reactions have some chance of occuring on a statistically viable level.

FOR WHAT IT"S WORTH...................

It is also most interesting that on just about every neutron generator manufacturer's literature and web-page, they list the reactions used to generate their neutrons via the D-D or D-T reactions, BUT NEVER MENTION THAT THIS IS FUSION!!!

Ya' think they might not want to step on delicate toes? OR Avoid the "F" word as in 'deadly' nuclear reactions?

You would think that someone out shopping for an "N" generator would not have to be coddled to or sheltered as they would be well aware of the reaction being fusion. But maybe not.


Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

ex-engineer
Posts: 18
Joined: Mon Jan 19, 2004 7:30 am
Real name:

Re: FAQ: Fusion ash/byproducts - endoergic d+d rxns

Post by ex-engineer » Tue Feb 10, 2004 12:49 am

John -

Here's a link to the ENDF data for cross sections on the two fusion reactions of interest, along with the (far) more prevalent elastic collision cross section: http://t2.lanl.gov/cgi-bin/endf?0,0,/in ... teron/H/dd

I'm assuming that the data is collected in a "black box" way such that a 1 MeV deuteron that actually has an elastic collision or two before eventually fusing is still counted as a fusion event. Someone who knows more about cross section measurement than I do (which would be approximately everyone who knows anything about it at all) might be able to set me straight on that.

My read on the data is that for every 12 1 MeV deuterons shot into a cloud of deuterium, ~2 will fuse. So your best case fusion 'gain', assuming lossless ion generation and acceleration, would be (10 + ~7)/12. It's tough to run a steam-driven generator on that...

Matt McConnell

ab0032
Posts: 86
Joined: Sun Oct 23, 2011 6:50 am
Real name: Alexander Biersack

Re: FAQ: Fusion ash/byproducts -Energy- How much?

Post by ab0032 » Sat Dec 03, 2011 1:09 pm

I really enjoyed this whole post. Really fun to read, nice demonstration of what is going on and putting things in the proper perspective.

I dont know if I am missing something here, but there is one point I cannot follow regarding the D-T and how to get to 50%. Is there something wrong with the powers of 10?

Richard Hull wrote:
> This would make our fusor contain 2X10e19 X 10e-5 = 2X10e14 deuterium atoms per cc at the stated operating pressure.........
> The fusor volume is 4/3 X Pi X 7.62^3 = 1600 cc..............
> This makes our fusor charged with a grand total of 1.6x10e3 X 2x10e14 = 3.2 x 10e17 deuterium atoms.

So we have 3.2x10^17 D, to get to 50-50, we have to options, if we want to stay at the same density, we have to run til we have 3.2x10^17 divided by 2 tritium and refill the deuterium lost, as we need 4 d for one t, or we burn 4/5 of the d , keep one fifth and produce 1/5 t from the 4/5. Then we end up with 2/5 of the pressure we started with, which is then less then 10 micron. Either way, we need a long time to get there, if we produce 1 million t per sec.

To produce 1.6x10^17 t at a rate of 1mio/sec or 10^6/sec, we need to run 1.6x10^11 sec. (To produce 1/5 of 3.2x10^17 takes almost as long.)

> Continuing to beat the poor dog..........
> We would have to operate the fusor for .5X10e7 seconds before we hit the ideal 50-50 D-T mix and were now a D-T fusor..... That is, after only 1 year and 5 months of 24 -7 operation, we would move from a 2 million fusion per second device to about a 200 million fusion per second device having morphed from D-D fusion to D-T fusion over this time frame.

So I get 10^11 sec and not 10^7. Since a year has about 3x10^7 sec, you will have to run about 3.000 years, til one approaches 50%

Did I miss some change in assumptions regarding fusion rate or something else?

A

Dustin
Posts: 105
Joined: Tue Jul 27, 2010 12:40 am
Real name:

Re: FAQ: Fusion ash/byproducts -Energy- How much?

Post by Dustin » Mon Dec 05, 2011 3:11 am

Great summary Richard,

The only problem I see is:

3. Proton (protium) - This ash product is in the form of a recoiling proton and carries a significant amount of energy, ( the greatest in the D-D fusion cycle ~3mev), from its related fusion event. It usually slams into the inner grid, but always winds up as common hydrogen gas by taking up a free electron. It, in theory could act as a poison of sorts as the fusor re-ionizes it and it speeds towards the center mixed in with deuterium ions. (useless, fusionless collisions) more on this later, as well.

The 3Mev proton will not (in all probability) hit the grid, it will continue in whatever direction it initially had and probably embed in the shell (or pass through it).
Steve.

User avatar
Richard Hull
Moderator
Posts: 11611
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: FAQ: Fusion ash/byproducts -Energy- How much?

Post by Richard Hull » Mon Dec 05, 2011 4:14 pm

All calcs were idealized and no intergration of the resultant fuel/ash change over time was taken into account. The thrust is, many years would be needed..... so forget all about using the ash as fuel in a fusor device. That was the bottom line.

Newbies are famous for looking at the D-D fusion ash, T and 3He, as new fuel. It ain't happening. We have our hands full getting the 100% load of D to fuse. The ash is nothing.

Finally, 99.999% of the protonic ash would never be attracted to the inner grid. A 50kv grid is not going to turn a 3mev proton. All would slam into the wall and 0.0000000% would pass through the chamber walls.

Due to shell bombardment, hydrogen embrittlement would take place over long periods of time and some of the buried hydrogen would start to pop back out into the gas environment once suface loading reached some saturation point as bombardment continued. Zero protium makes it to the outside would except through the vacuum exhaust ports.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Dan Tibbets
Posts: 578
Joined: Thu Apr 17, 2008 5:29 am
Real name:

Re: FAQ: Fusion ash/byproducts -Energy- How much?

Post by Dan Tibbets » Tue Dec 06, 2011 1:01 am

R.H. Just to throw in a complication. There is a proposed utilization of the tritium and He3 ash for additional fusion. This proposal by R. Bussard applies to a Polywell. As mentioned the fusion ash has way too much energy to be retained by the potential well. It would be neutralized as it hit the walls, and if not embedded, it becomes part of the neutral gas that has to be pumped out of the vessel. It could then be processed and reintroduced inside the magnetic/ electrostatic containment magrids as new fuel. In theory, since the D-T yields ~ will be ~ 6 times as much per fusion, the net fusion output of the machine may be as much from secondary D-T fusion as the original S-S reactions.

Of course this is based on the D-D Polywell being at least marginally successful with D-D fusion, and the fusion production would be in the MW instead of microwatts such as found in a gridded gas discharge fusor. As you pointed out the percentage of tritium available for further fusion (even if you could prevent it from embedding in the wall) would be tiny compared to the deuterium density in the fusor. Any tritium that is in the fusor space (after it has lost most of it's KE, and/ or charge exchanged, etc. may fuse faster than the D-D baseline, because while the tritium is extremely rare, each would be colliding frequently with the much more prevalent deuterium. This mixture modifies the fusion rate, though I'm uncertain of the formula to describe the interaction. It would be similar to mixing excess protium or deuterium with B11 or He3 to reduce the Bremsstrulung, while not slowing the fusion rate by a similar proportion. In the fusors case of course this would not make much (if any) difference in the total amount of D-T fusion, but the tritium present would not last as long as the raw tritium density would suggest. In otherwords the ~ 5-10 D-T fusions per minute may be misleading , if id is based only on the tritium density alone.

Dan Tibbets

Post Reply