Why the proportion of the Chamber and the Grid is 5:1?

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J Y Zhang
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Why the proportion of the Chamber and the Grid is 5:1?

Post by J Y Zhang »

Hi,
In FAQ, Richard Hull said that the proportion of the Chamber and the Grid is 5:1,and dC=0.15*kv.
How do you to get it? What is the whole equation of it?
Zhang
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Monroe Lee King Jr
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Re: Why the proportion of the Chamber and the Grid is 5:1?

Post by Monroe Lee King Jr »

I think it's just a rough estimate! If you know the speed of what your accelerating and that changes with energy I believe there is a more optimum ratio. In a regular fusor there is no magnetic field (other than that of the earth or local anomaly/field) also depends on gas ions or electrons your accelerating. But I imagine for your average fusor 5:1 is a good starting point indeed.

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Richard Hull
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Re: Why the proportion of the Chamber and the Grid is 5:1?

Post by Richard Hull »

Monroe is correct. There is no ratio. there is no commandment from on high. There is no rule or equation.

Common sense, functionality and traditionally successful designs range from a shell to grid ratio of 3:1 to 6:1 with most of the best fusors in the range of 4:1 and 5:1.

Any one thinking there is a magic ratio or equation needs to prove it in highly controlled experiment and a formal report. Something never undertaken by any living being.

Using the above ratios, assuming you pack the necessary gear, you will get fusion in a fusor.

In my FAQ I was virtually forced into such statements of ratios as all the newbies whine a bit about such things and need a starting point as most blindly bullhead into the effort on a rushed basis and want to be spoon fed information without troubling themselves with extensive reading or looking at images of fusors that work.
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Dustin
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Re: Why the proportion of the Chamber and the Grid is 5:1?

Post by Dustin »

Page 48 (and the rest of this document) has some useful info / data on grid ratio's vs neutron production.

http://fti.neep.wisc.edu/pdf/fdm1392.pdf

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Re: Why the proportion of the Chamber and the Grid is 5:1?

Post by Dustin »

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Richard Hull
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Re: Why the proportion of the Chamber and the Grid is 5:1?

Post by Richard Hull »

A giant fusor in amateur hands is about 8" in diameter. In small fusor's there is an issue with voltage limits, arcing, etc. the U of W fusor also ran at about 1/5 th pressure we run at due to the much higher voltages they used. (2 mTorr - U of W versus 10-15 mTorr - Amateur) These are efectively two different animals. Few amateur fusioneers ever hit 40KV, so we are on a different part of the cross sectional curve. We have had folks do a 1:3 ratio with little improved operation unless they used higher voltages. Our work is all over the place due to different levels of fit and finish, operating voltages, operating currents, etc. Fully 80-90% of all who have fused here either cannot do fusion today (moved on) or did'nt involve themselves in extensive research.

I would suggest that someone here that is properly instrumented for neutrons, perhaps you, could expose a 1:2, grid:shell size at 10+ mTorr and report back to us.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Why the proportion of the Chamber and the Grid is 5:1?

Post by Dustin »

The document I posted reviews the optimisation efforts of 4 different sets of researchers all of which essentially
reach the same conclusion, which is 1:2 ratio is better.(as much as 50%) some of these efforts were in smaller (20cm) anode which is 8"
and up to 40kv and the ratio stll holds. The pressure was admittedly 2-3mTorr on all though but this is well within reach of most amateurs though. I routinely get 10-^6 with my turbo.
Interestingly titanium coatings can give another 50% more neutrons. (but don't coat the cathode).

Section 3 pages 37 to 53
http://fti.neep.wisc.edu/pdf/fdm1392.pdf

I find it interesting however, that whenever I present any info to the contrary to what you have stated you seem to take it personally and insist rebuttal instead of acknowledging the info
for what it is. It is not my intention to launch any form of assault on your expertise or goodstanding on the forum,
but it does serve to remind me why I returned to lurking.
Steve.
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Richard Hull
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Re: Why the proportion of the Chamber and the Grid is 5:1?

Post by Richard Hull »

The original FAQ was advanced due to a large number of questions received by newbies who are looking for some gudiance, about 98% of whom will never do fusion, but who might do a demo fusor. Such first time and mostly last time efforts are done with limited knowledge and gear. Arcing in a weak vacuum enviroment is common. I advise on the small geometry to get these folks over a hurdle. Real fusioneers are already equipped to do as they choose and most pack the gear needed to look up the references and decide for themselves related to their future fusion efforts involving many skills which are already in hand.

This is not a confrontational event just a notation that the FAQs are not rigid design standards but guideposts to point new folks in the right general direction to warrant a decent first experience. If more advanced people here haven't given detailed reports related to larger grid sizes then they have either moved on or are happy with what they have. Most everyone in the advanced lane have read most of these old reports by U of W and U of I and have taken from them what they will.

Now that this issue is present. I will be very curious who will champion the 1:2 grid in an amateur system and report back. Most importantly someone who has a decent amount of experience and background with their fusor, who still has one operational. I have altered my FAQ to include 1:2 in the range.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Ross Moffett
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Re: Why the proportion of the Chamber and the Grid is 5:1?

Post by Ross Moffett »

Is there some resource list with links to these papers that I'm missing? I hadn't read these papers and find them fascinating.. particularly the methods they used to prove that fusion was happening mostly in free space, rather than in the plasma, and how they used that information to size their grid to 1:2. That information really calls into question the viability of the Bussard reactor, I think, since it's focused on improving the area of least fusion in the IEC reactor.
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Richard Hull
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Re: Why the proportion of the Chamber and the Grid is 5:1?

Post by Richard Hull »

Good Question. The old boys here have long known about the fast neutral-ion fusion results discovered at the universities. Most of us have read all or a significant number of the internet accessed papers. I am sure that most of these papers have been referenced in either the "files" forum or in many posts way back in the Theory forum. Few are those newbies that actually read, we have come to discover. The bulk are looking for a quick rinse and fast results, which seem to never shake out into their reality.

It must be reailized that a lot of the early work here and some significant references are bound up in the old "Songs" and "Intranet" hosted fusor forums when this amateur effort was young 1998-2002. I do not know if they are available. We have tried to drag them along with us as historical entities (Lots of embarrassing mis-steps are there, but the desire and verve shines through it all.)

A read of the FAQ on the history of the Amateur effort would explain a lot. This is our fourth and, hopefully, final hosting, but who knows. We have only been in this format since late April 2013.

EDIT: I have found that the songs listing is still to be found. I referenced it in the history of our fusion effort and the URL is still good. Read all about our 15 year effort at....

viewtopic.php?f=17&t=7580

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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