Jim Kovalchick -My attempt at smaller fusor

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Richard Hull
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Richard Hull » Thu Apr 09, 2020 3:52 am

Same here, the readings are dropping here as well. I never got even close to 100kn/s. Flash arcing will advance any neutron counting by >2k counts instantly, ruining the count run. Several arcs have been EMI powerful to the point that they have shut down the turbo supply (safety feature). (controller not hurt). I have popped the fusor supply breaker twice is severe arc conditions.

It is now fully decided to totally abandon the cross fusor as a rather worthless project for a guy like myself used to 1 mega neut/s with no sweat and no hassles. As I already noted the cross might do great for newbies looking for a quick win. I am going back to a modified fusor IV which will now take on the fusor V moniker in replacement. No light at the end of the cross tunnel save for that due to arcing which limits the top end. Give me the HV clearances and even electric field distribution, large surface areas for D2 absorption and desorption found in a sphere.

Keep up the reporting Jim. I can feel your pain. Sadly, this was the fastest pumping and best sealed system I have ever worked with. From dead start of the mechanical pump to sub micron in under 60 seconds!!

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.

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Frank Sanns
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Frank Sanns » Thu Apr 09, 2020 3:39 pm

What is the goal here; high neutron numbers or understanding how these contraptions work? It is an important question.

In my iterations of multiple grid electrodes, needle points, plasma electrodes, reverse polarity, non symmetrical, and the like, there is a different set of operating conditions that gives the highest neutron output. Some are paltry outputs and some are much more robust.

The standard fusor, made in a reasonably large chamber, is a near foolproof way to get good neutron production. With it comes limitations. One is that there is a unique highest current that can be put out at a given voltage with a particular configuration. That in itself says that things are not a simple as they might appear.

In the smaller fusors, alignment of these non traditional setups are going to be super critical. A miss in a big fusor is nearly negligible. In these smaller fusors, alignment will need to be closer to laser cavity mirror alignments than the big ole wire grid fusor.

As for flash arcing, try rounding off some of the edges and cut them back a little to give more relief.

Don't give up. Be more observant and more meticulous in your methods and you might be rewarded some very good neutron numbers.

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Frank Sanns
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Frank Sanns » Thu Apr 09, 2020 5:08 pm

Jim,

Somehow my post response to you was lost. I think you may have deleted your post while I was responding. Here is another try.

No insult intended to you or Richard. My post was more directed at the new work that Richard is doing. I just did not want him to give up.

When I was out visiting Jon Rosenstiel a couple of months ago, we looked inside his cube. It was very clear that some micro mechanism was going on there that is not normally seen in a conventional fusor. I simply was trying to convey some of that info to add to the data base. I know you are Richard are extremely throughough. No insults or demeaning intended. None. Zero. Sometimes I just write and forget the "tone" on a technical forum. My bad. Keep up the good work!

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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick » Thu Apr 09, 2020 5:39 pm

No worries Frank. I reconsidered my response because I am aware that written posts shouldn't be looked at that way. I appreciate your contributions to my efforts.
Best regards,
Jim K

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Mark Rowley
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Mark Rowley » Thu Apr 09, 2020 6:15 pm

Fwiw, I went through a multitude of grid sizes before I found the sweet spot with one of 0.45” diameter. I started with one around 0.85” and experienced many of the problems you and Richard have pointed out. Once the 0.45” was installed everything began running smoothly. Other than that, I do use an alumina insulator for the stalk and my grid is tungsten. And of course it’s a classic grid and not a tube design.

Input power seems to be a bit different as well. 10mA input seems excessive, at least from what Ive learned with mine. 3.5mA at 45kV with ~35mTorr of D2 should easily put one at near or over the 500k n/s range. With my system, 10mA at 30kV would only serve to overheat the grid to astronomical levels. If you haven’t yet, try raising the flow and pressure of D2. Strive for higher voltages (40-50kV) with current draw below 5mA.

Mark Rowley

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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick » Thu Apr 09, 2020 7:19 pm

Mark,
In my fusor I dont bother looking at chamber pressure except to just double check every so often. I set my current using either my voltage or by adjusting my chamber goes ins and goes outs.

Yes, 10 mA is too much for mine if I run for much time at all. 5 mA is also depending on run length. I really want to try a section of tungsten tube for my next grid. Stainless cant hold the temp. I may shorten my grid a little to give a little more clearance. I had tried tungsten before, but I want to try again.

Jim K

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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Dennis P Brown » Thu Apr 09, 2020 7:51 pm

I've posted in two other threads on this topic today, which makes me think that the implications of my previous work wasn't fully understood.

What I am posting and trying to make clear now is that the dominate effect of a "small" chamber isn't its size (volume) so much as its higher operating deuterium pressure. As I showed in my posted experiment, a large chamber can easily be made into a "smaller" chamber simply by installing a wire cage to act as the primary grounding plane around the HV cathode.

This allowed me to operate my "apparently small" chambered fusor at far higher pressures in my existing large chamber machine as if it was really a small chamber. My 50% reduction in 'apparent' volume allowed my existing fusor (previously capable of around 250 K neutrons/sec) to increase its yield by also 50% (roughly.) This certainly was an advantage using my same power supply (identical voltages & current.) However, this increase neutron count wasn't due to a smaller physical chamber alone. Rather, just the obvious effects of operating at a higher fuel pressure.

Now, it is true that there are specific advantages to creating smaller chamber fusors - they can be lower in cost to obtain (a few vacuum components) and offers ease of little to no manufacture issues (off-the-self components); better still, for a given power supply, it can offer more neutrons (very useful, especially for a marginal supply.)

On the other hand, smaller chambers appear to offer more difficult design issues relative to the cathode (as posted by others here)and require very careful control of voltage (this I discovered after making my own, actually smaller chamber to test this experimental idea further.) I did not like operating that small fusor. It posed a lot of control issues and after many attempts dealing with those issues, I retired it as not worth my time (I had a working large chamber, anyway.)

Aside: sorry for posting so much but I do want new users to understand that small chambers aren't necessarily the best route to fusion. As Richard said, these machines do offer another method to reach the goal of creating neutrons. They aren't really superior to normal large chamber machines. Its what one is looking for - join the neutron club (and likely leave) or have a machine available that allows experimental versatility (like my large chamber that easily converted into a small one.)

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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Mark Rowley » Thu Apr 09, 2020 9:34 pm

Dennis,
I completely agree with your theory on D2 pressure. 100% concurrent with my findings as well as what others have said in other forums and groups.

However, your last two paragraphs are problematic, at least from my experience. Firstly, cube and cross Fusors have easily broken the mega mark and are deeply into the realm of being “research grade”. To say they aren’t is nothing short of inaccurate and misleading. Secondly, the difficulty of addressing the cathode issues are no more difficult than finding, assembling, and paying for what a large chamber device demands. The power supply alone for a large chamber device is a monumental effort just on its own. Yes, no one said this is easy but casting undue criticisms and stones at the smaller systems only serves to offer counterproductive doubt in the minds of new folks getting into the hobby (as seen in one very recent post).

It’s too bad the same enterprising and optimistic mindset the group had 20 years ago isn’t prevalent with the smaller systems. Highly likely if a cross or cube Fusor was introduced in 2000 the present day negativity would not be seen.

Mark Rowley

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Jim Kovalchick
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick » Thu Apr 09, 2020 10:39 pm

Dennis,
I'm not sure why you posted on the thread about my fusor that your earlier posts were being misunderstood. I fully understand that to take the same voltage position on the Paschen curve for a smaller effective plate difference means that gas pressure will need to be higher. The early successful small fusor builders well before me knew about it, and the extra pressure has been discussed by me and others in past posts.

Reading my posts, you will see that my issues are have been related to material and operation considerations.

I went after a smaller fusor because I was intrigued by the success of others. The smaller fusors have been putting out decent tier numbers and you can get cliserto a higher flux for the same neutron production rate because the fusion chamber is compact. Hence Jon R's crazy good silver foil activation to 5000 com. These devices work. There are design challenges as you pointed out, but people have found ways to make it work.

With regard to putting an inner grid into a larger chamber, of course it has the same Paschen effect, but I think it's only needed if the chamber is so big that to get to s desired spot on the curve you have to drive pressure to a point that small amounts of chamber outgassing will be significant in comparison to the amount of deuterium. Also taking closer tolerances with a secondary or inner ground grid can produce the same challenges to arcing as clearances in a small fusor does. Choosing an inner ground grid in a bigger fusor may work, but it necessarily will expose a lower workable flux for the same tier. Richard brought up that he is concerned about a small cross fusor not presenting a uniform surface for ion interactions. He may have a point, but again I counter that others have made it work.

To close my rant: my problems are not about understanding how fusors work. My problems are engineering related.

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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick » Thu Apr 09, 2020 10:42 pm

Mark,
Your post went up as I was drafting my last. I agree with your premise. Thanks for posting it.

Jim K

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