Matt Gibson Fusor

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Finn Hammer
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Re: Matt Gibson Fusor

Post by Finn Hammer »

Just a short note, the above post of mine, boasted 45kcpm, but that was wrong, it was 4.5kcpm, my bad.

This has been edited in the original post.

Cheers, Finn Hammer
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Richard, Finn - Thank you very much, excellent news! I am excited!

I definitely couldn’t have done it without the help from you guys and many others that came before, succeeded, and provided their results, knowledge, and expertise to this forum…I’ll be sure to well document my future efforts as I continue on!

Next up will be the silver activation and then rhodium (I’m watching for some good deals as the price of rhodium looks to be down). I need my Hdpe to hurry up!

After that, I need to upgrade me PSU. I have plenty of current capacity left, but find that the fusor really starts going once I break past 35kV. At 40kV, it’s begging for more volts!

Also need to get some air moving across this thing as it heats up FAST.

Edit: Now I need to look into calculations for TIER for this fusor/scintillator combo.

-Matt
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Matt, Your fusor has a wire grid if I remember. There will be hot spots, (good neutron emission), probably near the central region of the cross. This is where you need to put your moderator when activating and the Ludlum when counting. I bought my tiny Rhodium strip of foil when Rh was only $10,000/troy ounce. I paid a bit over $600 for it. I plan on buying a larger Rhodium target, but will wait until Rh drops well below $4000. Good luck on the Rhodium.

Definitely stick with 999 pure Silver for a while to get your "activation legs" on a firm footing. Sheet pure silver can be had from Rio Grande. Just make sure not to purchase Sterling silver sheet for it is not pure. (8% cooper content.) Coin silver is only 90% silver. Stay with "fine silver" .999pure.

Indium is also good. Go to Roto metals for small pieces of Indium and you can pound the stuff out with a hammer to sheeting. It is like play-dough. If you get a big chucky piece, melt it in a small pyrex glass or porcelain dish, it is easy. Get a flat piece of sheet steel and kind of sling-pour the metal out onto the sheet this should freeze into a longish slender mass that is less thick. A thin portion off this pour will respond much faster to being pounded out to a sheet-like activation target.

I appreciate your broad thanks for the help you have received. I am thankful for all that I have learned over these many years from others as well. It is well to realize that much of what you have read in the old posts and replies from others, perhaps long gone now, was of real value. Even though I have written the bulk of all FAQs, the responses from others in those FAQs have added much of critical value to them. That is the value of the term "open source" in this forum.

Recently due to a number of factors, the forums are alive with information and folks like you getting stuff done. This is always a good thing. We keep growing, learning and teaching.

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
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

I see what looks like two very very faint, purple, beams going side-to-side within the chamber, through the loop openings that make up the cathode. I don’t see any other beams. This looks a lot like what I see in the ring cathode design…Is this normal for a three ring wire cathode?

Anyways, putting the hammer on the side of the chamber produces the highest detection. No room for improvement there.

I am seeing plenty of condensation in my syringe, so I assume my fuel cell is producing “wet” deuterium. I will get some drierite on the way home today and add some to the syringe to see if this makes a difference. If so, I’ll plan for a better way of drying my deuterium rather than a half assed approach :-)

My system seems to be happy at 18.1 microns, 40kV-ish, and 7mA. If I raise the pressure, my voltage drops (and stays lower) while my current rises higher. Neutron production drops. I’m already at my max voltage so I can’t lower the pressure without tripping the psu off.

As I understand it, higher current will also increase neutron production? I have more than double the capacity available…Am I tapped out based on my chamber/cathode configuration?
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Liam David
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Re: Matt Gibson Fusor

Post by Liam David »

Your chamber is cylindrical, so there will be a preferred plasma formation axis even with a spherical grid. Since your grid isn't perfectly symmetric, this effect is exacerbated.

Higher current for a given voltage = more neutrons, almost exactly in a linear relationship. Double current = double neutrons.

If the Glassman is cc/cv, I don't see why raising the pressure at 40 kV / 7mA drops the voltage unless you're current-limiting the supply via the front-panel knob. Raising the pressure should raise the current to 15 mA, only after which should the voltage drop.
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Matt,
What you are telling me leads me to assume that your supply impedance is the limiting factor here. Beef is needed and it ain't there. Regardless of the supply ratings and claims, it is folding up with the addition of gas. This is actually quite the norm, however, with beefiness in the supply the voltage can be raised and the current will rise as well after adding more gas pressure. You have discovered your classic "rope limit" with your supply. Reducing the pressure should allow more voltage to be applied, sliding you up the cross sectional curve, but the current will be limited in the end, I would think. More of a watt limit maybe, at this point. Our supplies regardless of beefiness limit all but the most well heeled. Those with the ultra beefiness in their supplies will hit a voltage limit as some point where breakdown in the reactor will be the limit. Let us hope they have a more than adequate ballast or fabulous protection electronic guard dog for arc level protection. Even a 150kv 50ma supply coupled with a fusor, will see their combined limit due to any number of possible limiting factors.

I have 45kv as my voltage limit with an almost unlimitied current. However my ultimate limit in the heating at 45 kv @20ma and its 900 watt heating effect on my uncooled fusor will, in short order, create electron runaway with my tungsten wire grid. Please note the following realities I am faced with. My input 60hz AC current to the x-ray Xfrmer for smooth operation is about 250 volts (variac boost) at 4.5 amps and this happens at about 38kv out of the rectified DC supply. However to get the huge core saturation needed to claw my way to 45 KV @20 ma (900 DC watts) requires the AC input to be 250 volts @ 8 amps or 2000 RMS watts!!! Limits are limits and we learn to live with them. My poor X-ray transformer core and primary take it on the chin over about 41kv. The poor transformer hum in protestation is easily heard at my rope limit. Naturally 2000 watts in to get the 41kv @10.5ma 430 watts in my most recent run is fine with me and especially my power company, but I really feel for my poor transformer.

As I have said for years with the Tesla coils at 12,000 watt draw of Nemsis at its peak and now my fusor wasting energy......The power company and I have a deal going between us. They agree to give me all the power I am willing to pay for. At about 8.5 cents per KWhr, coupled with short burst usage, I do not see this in my monthly billing.

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: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Liam,

I may need to check this to see if my current knob is fully rotated. I usually just rely on the indicator light that lets you know which is limiting the output (voltage or current can be set). It’s disappointing to have 600w available and only be using half.

Any thoughts on “wet” deuterium? I know that in general, anything else getting into the chamber will get in the way of the deuterium, but has anyone shown just how much wet deuterium affects operation?

How about temperature of the chamber? I’m hitting over 200F. At what temperature does performance begin to suffer?

Edit: Richard, does the load matter all that much to a supply like this? Seems it should be able to handle whatever is thrown at it up to its current/voltage limiting circuits. Maybe I should use a backup current meter to see if the PSU current meter is accurate?

-Matt
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Liam David
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Re: Matt Gibson Fusor

Post by Liam David »

I'm not familiar with Glassman supplies but the light probably comes on relative to the knob setpoint and not necessarily the absolute limit. Check the knob!

I'm not aware of any quantitative studies on how wet deuterium affects operation (anyone?). Nonetheless, it's obviously best to have minimal water vapor. One would have to look at the charge exchange and scattering cross-sections to get an idea of the magnitude of the effect.

A hot chamber will outgas more water and other gases, and will reduce deuterium absorption which reduces beam-target fusion. I tend to stay below 100C, but more for my o-ring seals. I see a noticeable drop in performance above ~80C.
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

I am with Liam! I will usually end all running of my fusor at about 80 deg C as wall unloading coupled with electron runaway lay ahead. In a well adjusted fusor V I am usually up to about 800,000 TIER at this point, but it varies. After shut down the other night at 85C, with zero power applied it coasted nicely up to 98C before cooling in my 33 deg F lab. I assume this is stored thermal energy in the giant 8" CF rings.

If and when I do another fusor, I will endeavor to actively cool it in some fashion.

Yes, as Liam suggests, monkey around with you supply to see if you can do better. Claims by manufacturers will forever be just that. Read my neon transformer post. 15 kv @ 30 ma is a joke and an impossibility. 0.1 microns on a mechanical pump is a dream, as well.

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
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Sounds good guys…I’ll work on cooling, drying the gas, and may reach out to Glassman (they’ve been recently responsive) if I can’t get current to increase. I can’t imagine a multi thousand dollar (when new) psu would cut out at half the advertised specs without some other issue in play. Fingers crossed!
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Re: Matt Gibson Fusor

Post by John Futter »

you will find that your supply is responding to little arcs that are hitting the current limit so short in time that you are not seeing it on the current limit led.
You need to delve into the Glassman current control circuit and scope it. What value is your ballast resistor??
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi John,

I’m using a 50kOhm ballast resistor.

Would I be able to see anything happening in the chamber? It looks pretty stable to my eyes…

Every now and then, I do see the current flicker (very briefly drop low and immediately return to 7mA).
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Okay, so while I haven’t solved the issue with current, I did find a potential issue with the MFC…It leaks!

I let the syringe run out and saw that I’m still getting around 4 microns with the MFC valve open. Closing the valve allows me to run down below 0.1microns. Assuming it was the syringe, I removed it and put my finger over the hole to the barb. Still 4 microns. Taking off the barb and trying to plug the Kf25 to vcr4 adapter, 4 microns. I removed the MFC and twisted the adapter a litter harder…

STILL 4 MICRONS!

Do I have an internal issue at this point? Or are these vcr fittings just tricky to get right?

I then took off the adapter and tried plugging the hole directly to the input. Still leaks. The rate of the leak increases as I open the valve more and more, decreases as I close the valve.

What’s going on here?
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Liam David
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Re: Matt Gibson Fusor

Post by Liam David »

MFCs almost always have a slow thru-leak and are not meant to be shutoff valves. If I leave the reservoir behind my MFC pressurized, it will cause the chamber pressure to rise to dozens of torr of deuterium overnight. Your finger won't be a good enough seal at 4 mtorr, and even if it were, the residual air upstream in the MFC will buffer the leak for a little while. Unless you have messed up sealing surfaces and gaskets, VCRs are hard to get wrong. Alternatively, are you sure it's related to the MFC?
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Liam,

If that’s true, then maybe I overreacted…I was surprised to see my turbo unable to pull below 4 microns with the valve open and syringe connected…

While I don’t use the MFC as my main valve to the chamber (there’s a bellows valve connecting it to the chamber), it does hold pretty well on its own when closed. I can pull below 0.1 microns pretty quickly.

Is there a proper way to check that it’s functioning properly then? While it was stuck at 4 microns, I took a can of duster and sprayed it directly at each connection along the way to the MFC. I didn’t notice any jump in pressure, would this be acceptable?

What a long day it’s been…
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Turbo won't pull below 4 microns??!!! Something is wrong there. For a turbo, that is more than a slow leak.
Like Liam noted MFCs are not valves. I once thought this, but tested some of the ones I have. A learning experience for sure. One might think they are valves, but no, sorry.
I have had ten MFC's in a box in the attic of the lab for years and never had the slightest inclination to use one. Long ago I decided to control my flow rate against the secondary pump with a superior manual bellows valve. The gas lines now have a superior sapphire control leak valve. Adding this leak to my gas system two years ago was a godsend. This combination, artfully operated, allows for great control.

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: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Richard,

With the syringe connected, and empty, MFC valve still open as if I were operating, the turbo won’t pull lower than 4 microns. As soon as I close the MFC valve, it quickly pulls it down.

Let’s assume this is an actual leak during operation. Would I be able to operate the fusor? 4 microns of air seems like alot to get in the way of the deuterium, no?

How about a test: I’ll disconnect the syringe, set the MFC to allow 4 microns of air, then connect the syringe and operate as normal. Would this completely inhibit operation, or just reduce output?

Edit: I realized that my test is a little more complicated as my system would quickly remove the air…
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

I wish I could help here. But I worry that this is not air, but water vapor perhaps now in the gas system. Condensation in the syringe is very, very bad.

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: Matt Gibson Fusor

Post by Matt_Gibson »

Yeah, I’m still working on a simple way of drying my deuterium. Putting Damprid directly into the syringe just clogged the syringe. It did dry it up though, but made gas delivery very erratic. I’m now cobbling together some hose barb fittings and large diameter tubing to put inline with the fuel cell and syringe…
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Small update: I was able to push more current though the plasma. At 16.8 microns, which required a flow rate of 5sccm this run, and 39-40kV, I was just under 12mA. As I pushed further, the PSU kicked it down to around 7mA. Backing off the dial, and then ramping back up, I could approach 12mA again, but not exceed it. This run got me up to 10mR/hr.

At this point, the tungsten cathode is so bright that I can’t see any hint of plasma anymore. I think that one of two things is occurring:

1-Temperature is so high that I’m having issues with electron emission/thermal runway problems as I have yet to get a fan blowing across this thing.

2-12mA is actually 15mA and the psu is current limiting. I had to replace the mA meter and adjust an internal trimpot. It’s possible that I didn’t adjust correctly and my meter is indicating 12mA instead of 15mA.

Edit: Looking over the data-sheet for this psu, I overlooked a critical spec! While it can do 15mA and 40kV, it limits at 500w, not 600w. Dern…Now it appears that I am probably maxed out and that’s why I can’t get beyond 12mA when at/near 40kV…
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Re: Matt Gibson Fusor

Post by Rex Allers »

Matt, I thought I remembered the 15 mA not being available at the high-end voltage output, so I looked at the data sheet. Then I noticed your edit on the last post so I see you already figured out why you can't get 15 mA.

Here's more detail...
I think I remember you have an EW 40kV supply.
Here's the 1st paragraph from the datasheet you already found,

"The EW Series is a 500 watt regulated high voltage DC power supply with an important difference...maximum current ratings are equivalent to a 600 W supply! This maximum current, which is available for all output voltages up to 84% of rated voltage, should be of significant interest for many applications."

So sounds like there's change from 600 W to 500 W at
40 * .84 = 33.6 kV

Above that it becomes a 500 W supply so current at max HV is
500 / 40 = 12.5 mA

So what you are seeing is as it was designed.

But now that I think about it, when is it a 600W (!) supply? Checking the math, Never.

500 / 15 = 33.3 kV , which is about the .84 of max voltage, so it is always a max of 500W. I guess the mention of 600 W is just nonsense marketing BS. In fact the beginning of that paragraph and the title of the datasheet says it is a 500 W supply.
Rex Allers
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

All in all, I guess 500w and -40kV isn’t bad for now…Wish there was a way to push it to 600w.
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Matt, you are doing fusion, good fusion, experiment capable fusion. Play with what you have a bit. Learn as you experiment, not only the physics, but the operation in great detail. There are always future possible supplies once you have plumbed the limits of what you have. Too many often go off in the search for the better, before they have fully secured the benefits of the good.

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: Matt Gibson Fusor

Post by Matt_Gibson »

You’re right, Richard. I tend to have a lead foot and love pushing things harder and harder once they get going!

So which direction should I be going in (as far as maximizing performance goes) at this point? Should I work on a better cathode? It’s pretty large (had to push it through the conflat opening to get it into place). Cooling seems like a low hanging fruit…

-Matt
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

All of it is your play ground. I would really concentrate right now on doing great activation. You are not super limited, just hobbled a bit. Silver and indium are going to be easy for you right now, at your level. Play with these. Try varying the neutron oven thickness between your fusor and the elements you activate..

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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