Fusor Forums

I have done some research into dense plasma focus.
It seems substancial improvements in neutron yields occur
when a few percent of argon is present. The argon plasma
acts as a tamper or reflector to the pure core of burning
deuterium. Argon could act as a relector around the fusion
cavity in the fusor. It could reduce losses from the core
by reflecting deuterium ions back to the center.
The heavy ions would tend to hang around the negative electrode openings.

Larry Leins
Ole Miss Grad Student

Now theres an idea thats not immediately obvious. Sounds easy to test as well.
This has stimulated another idea, could adding a small amount of neutron moderators and absorbers, such as hydrogen and boron 10, reduce the neutron output of the system without affecting performance too much?.

Not such a good idea for neutron counting, of course. But maybe the neutron "radiation" could be "sheilded" at source, and possibly turned into recoverable energy (Li7 ions and alpha particles)

IJV

I can't imagine that adding any amount of moderators and absorbers to the gas mixture would have a significant effect. Neutron interactions are rare enough at everyday densities - with the minuscule, wispy bit of moderator that you would have by adding a small amount of gas to a vacuum system, I would think that neutron/moderator interactions would be so rare as to have almost no observable effect.

-Ryan Edgar

You could well be right, but then I wouldn't have thought that adding a few percent of argon would improve performance, for those very same reasons.

However, all of this might only apply to Dense Plasma Focus systems and not to the IEC systems.

How difficult would it be for someone to do a rough test of whether adding a few percent argon to a fusor has any effect on performance?.

cheers
Ivan Vuletich

This post may be kind of bad (went to a concert last night), but:

It is entirely possible that adding a second gas could affect performance. I can think of a couple of ways:
1) Buffer - lasers often use a "buffer" gas to change the thermal characteristics of the lasing material. These buffers can also be used to change the relaxation properties of the material. It is possible that a second gas introduced into the fusor could allow for a more dense plasma, could improve heating of the plasma, etc.
2) Reflector - the gas could reflect neutrons back into the plasma. This would lower the electrostatic repulsion of the plasma by introducing more neutrons. I have to agree that this effect should be small.
3) The gas could alter the quantum properties of the hydrogen in some unforseen way, changing the value of sigma (cross section) to allow higher neutron production.

I could be having another stupid day, but I think that those were fairly good for random thoughts.

Based purely on my fusion experience and book readin', I think Ryan is correct on the moderator, reflector idea. There is no possible way any such gases could shield, suppress or reduce neutron production by so much as 1 single neutron in a practical sense. These are all fast neuts and the cross sections of all matter to fast neuts is microscopic even in bulk solids, much less a millionth of an atmosphere of pure absorbing hydrogen.

As regards Argon boosting neut production, that is another matter, and is worth investigating. The mix might be critical. If it is, a really precise dual mass flow system might be required or at least an isolated deep pumped reservoir to which known atomic volumes of the two gases could be mixed accurately via sensitive pressure readings.

To get quantitative data, assuming the effect might boost by a few percent, a very stable and repeatable fusor operation must be obtained. (Very tough to achieve, believe me!)

Richard Hull

I meant only to reflect ions not neutrons.
By increasing the sigma in theory more neutrons.
More density at the core..more probability of reaction.
Recirculation of deuterium ions back into the core by bouncing off heavier argon ions at the negative grid.


larry leins wrote:
> I have done some research into dense plasma focus.
> It seems substancial improvements in neutron yields occur
> when a few percent of argon is present. The argon plasma
> acts as a tamper or reflector to the pure core of burning
> deuterium. Argon could act as a relector around the fusion
> cavity in the fusor. It could reduce losses from the core
> by reflecting deuterium ions back to the center.
> The heavy ions would tend to hang around the negative electrode openings.
>
> Larry Leins
> Ole Miss Grad Student

I think that putting in Ar will fuck with things. The Ar is much heavier than the duetron and the momentum transfer from Ar to D will shot the D out of the system. However, your idea is not totally flawed. If you had a secondary grid envolping the entire aray with sufficent voltage you could keep the D in play with a higher D kinetic energy. Although I don't think that this is the answer to higher fusion rates.

I think that the best thing a person can do to recycle energy losses in the fusor is to have some sphereical envolpe that absorbs the light emitted from recombination and then emitts an electron that then ionizes another D2. This would be either a spherical hot cathode, or some photoelectric material w/ a low work function, or even a hot cathode low work function photoelectric material.

If one were to pursue (sp?) a "momentum trap" such as described by Ar atoms you have to remember that the trap works both ways; that is to say it reflects the D ions in AND away.

Sometimes Ar is used a thermal conductor in plasmas, it helps equilibrate the electrons temp. w/ the ions temp..