Questions regarding Boron fuel

Discuss how polywell fusion works; share theoretical questions and answers.

Moderators: tonybarry, MSimon

[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable
SymenJ
Posts: 8
Joined: Tue Feb 24, 2015 4:15 pm
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Questions regarding Boron fuel

Postby SymenJ » Sun Jun 14, 2015 12:53 pm

Dear all,

For my research regarding the boron fuel and market for the polywell reactor I got into contact with someone from Convergent Scientific. I asked him some questions on the market and on the preferabel fuel type for the Polywell reactor. As I heard from several on this forum that decaboranes is the way to go, I asked him several question on it. He mentioned that the generally accepted easiest way to fuel pB11 burning devices is gas injection of borane (BH3), diborane (B2H6), or tetraborane (B4H10). However these gases are chemically volatile and/or toxic, and the relatively large molecules make controlling ionization location within the plasma more difficult. They are currently investigating the viability of using pure crystalline boron ion sources.

Can anyone comment on the use of Borane, Diborane and Tetraborane? How does the inonization proces for these compounds work? Can anyone expain me the ionization location issue mentioned? And what about the pure crystalline boron?

Thanks,

Symen

hanelyp
Posts: 2255
Joined: Fri Oct 26, 2007 8:50 pm
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: Questions regarding Boron fuel

Postby hanelyp » Sun Jun 14, 2015 11:46 pm

For the small quantities of material used as fusion fuel toxicity is a manageable difficulty. Given the annealing process expected in the polywell I don't see it as vital that ionization take place in a restricted location, so long as the fuel is properly ionized before it can escape from the central zone.

Crystalline boron is a somewhat refractory material. I expect ejecting ions from a boron crystal would be difficult.
The daylight is uncomfortably bright for eyes so long in the dark.

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: Questions regarding Boron fuel

Postby D Tibbets » Mon Jun 15, 2015 4:11 am

I know little about the ionization process in various devices, except for... Sputtering is a process of blasting or eroding a solid into an atomized cloud of small blobs- a few molecules thick(?), by bombarding iyt with other ions, or probably electrons. This is used for vacuum deposition coatings of mirrors and many other objects for optical or electronic purposes. Further atomization and ionization proceeds along similar lines. A electrical field is very poor at ionization. Using a pointed needle electrode helps some as this concentrates the electrical field, but most ionization is due to electron bombardment. Once you get a few free electrons such as from thermoionic emmision from a hot cathode (old vacuum tube technology) these electrons knock of further electrons from a electron donating neutral gas or surface-almost any substance. These secondary electrons knock off further electrons, etc, untill ionization stops because all of the electrons have been striped frooom the atom, or the average energy of the free electrons drops below the ionization potential for the various electron orbits for a atom. Because of thermal spread and some recombinations will occur even in a plasma with an average temperature well above the ionization temperature/ energy of that atomic species. This recombination is what produces most of the visible light seen in a plasma. Black body radiation may contribute some also, as I've read that the Bell curve of black body radiation will always have a low energy visible tail glow. In any case. this cascade of ionizations occurs quickly. In the Polywell Bussard stipulated that the doubling period for the ionization cascade occurs over a couple of micro seconds, and that very high ionization rates can occur over periods of less than 100 microseconds. In A small machine a neutral gas ion cal travel a significant percentage of the machine diameter before it ionizes. As significant portion of this neutral gas may pass outside the machine without ionization. This was demonstrated by the build up of neutral gas outside the magrid of WB6 after it was initially puffed into the magrid volume. This buildup of non contained gas led to the arc breakdown that terminated the expirements after a few milliseconds. A larger is supposed to have less problems with this as the transit time for the puffed neutral gasis longer- it takes longer to transit the machine. Bussard felt that this would allow gas puffing in say a 3 meter versus the 0.3 meters of WB6 with much less gas escape and also a larger portion of the gass ionizing at preferred locations near the Wiffleball edge- top of the potential well. Gas that ionized deeper/ later would experiance a lower potential well.

An ion gun that produces the ion outside the magrid may offer better control and manipulations. It is similar to gas ionization , though other modalities such a microwave ionization enhancement and some other tricks used in ion gun/ ion rocket engines, may be employed.

Hydrogen has an ionization energy of ~ 11 eV. Any electron at higher energy that hits the atom will probably result in ionization. I don't know what the ionization energies for the 5 electrons in Boron is.

Other methods of producing ions/ neutral plasma to feed the Polywell may actually use other plasma producing concepts. A field Field Reversed Configuration or Helicon (I am foggy on what this is) may feed the ions, boron or otherwise into the Polywell. Laser ablative beams, electron beams on solid targets may be used to convert from a solid to a gas and then at least starting the ionization process. Lessons from the vacuum coating industry, and other fields may be very useful. This all falls under on the convenient engineering issue hand waving. Persueing the physics can tell weather an end goal is possible and reasonable. The engineering is what makes it actually happen.

Dan Tibbets
To error is human... and I'm very human.

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: Questions regarding Boron fuel

Postby D Tibbets » Mon Jun 15, 2015 4:29 am

To error is human... and I'm very human.

ladajo
Posts: 6204
Joined: Thu Sep 17, 2009 11:18 pm
Location: North East Coast
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: Questions regarding Boron fuel

Postby ladajo » Mon Jun 15, 2015 9:15 pm

Assuming 100% burn.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

SymenJ
Posts: 8
Joined: Tue Feb 24, 2015 4:15 pm
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: Questions regarding Boron fuel

Postby SymenJ » Tue Jun 30, 2015 6:03 pm

Ok and what about DD fusion. Does it so happen that the protons form deuterium which in turn fuses with another deuterium particle? If yes what are the percentages one can expect compaired to proton boron fusion. (i.e. if one has to calculate the amount of boron necessary for a reactor with a capacity of say 1000 MW)

Thanks

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: Questions regarding Boron fuel

Postby D Tibbets » Wed Jul 01, 2015 12:06 am

To error is human... and I'm very human.

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: Questions regarding Boron fuel

Postby D Tibbets » Wed Jul 01, 2015 12:30 am

In order to answer your actual question more fully, a P-D fusion reaction is possible, but extremely less likely than the other reactions of interest. A P-B11 reaction is perhaps the holy grail of fusion, but it is also the most difficult of any Reasonable fuel choice. D-T is easiest, followed by D-D, then D-He3. D-Lithium reactions are less favorable than the P-B11 reaction. The fusion proton only serves to give up it's energy through wall impacts or direct conversion. Protons are cheap and stupendously available (hydrogen). There is no advantage in trying to recycle it in a non ignition machine.

The problem with D-T and D-He3 is that the tritium and He3 is piratically non existent on Earth. The fuel has to be produced or mined before it can be used. Tokamaks and other tritium based machines have to produce their own tritium at rates and costs less than that expended in the reactor. This untested challenge is a further step between a proof of concept machine like ITER and a DEMO machine type prototype.

The Polywell and perhaps some other designs that may operate fairly well with D-D fuel alone have the option of boosting their output by recycling the tritium and possibly He3 so that the final fusion cross section products end up being (more) profitable. The tritium problem is very significantly eased if the production versus consumption of tritium does not have to be over unity.

I wonder if a Tokamak might utilize some D-D fusion in the dominate mixture of D-T fusion.. It probably could not reach anywhere near Q>1 with this fuel, but this 'side reaction' is unavoidable. At rates of perhaps 1 percent of the D-T fusion rates it would produce some additional neutrons and tritium directly. If the lithium blanket with beryllium and or lead boosters does not quite produce enough tritium, this D-D side reaction may give the small extra tritium boost necessary to keep the machine running.


Dan Tibbets
To error is human... and I'm very human.

SymenJ
Posts: 8
Joined: Tue Feb 24, 2015 4:15 pm
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: Questions regarding Boron fuel

Postby SymenJ » Sun Jul 05, 2015 11:41 am

Maybe I was not too specific with my question but what I actually ment was DD fusion during p-B11 fusion.

D Tibbets
Posts: 2775
Joined: Thu Jun 26, 2008 6:52 am
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: Questions regarding Boron fuel

Postby D Tibbets » Sun Jul 05, 2015 7:18 pm

To error is human... and I'm very human.

ladajo
Posts: 6204
Joined: Thu Sep 17, 2009 11:18 pm
Location: North East Coast
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Re: Questions regarding Boron fuel

Postby ladajo » Mon Jul 06, 2015 12:39 pm

I wrote in a thread on this a while back and as I recall gave production rates and energy estimates.

Too busy to search for it right now, sorry.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)


[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable
[phpBB Debug] PHP Warning: in file [ROOT]/vendor/twig/twig/lib/Twig/Extension/Core.php on line 1236: count(): Parameter must be an array or an object that implements Countable

Return to “Theory”

Who is online

Users browsing this forum: No registered users and 3 guests