Matt Gibson Fusor

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Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Richard,

Great to hear! It was definitely exciting to see.

I had a bad practice of laying uranium rocks (Autunite and torbernite included) directly on the probe screen. Since mine are all on the high end, I didn’t notice that I was contaminating the probe (my rocks all need to be on the x100 scale). Somewhere in there is a spec (- black light might help if it’s Autunite in there). :-( It’s probably risky to attempt to remove it, so I just keep it for my rocks. If I find a good deal on a new one, I’ll probably get it :-)

1000cpm is a start, I’ll keep working on the upgraded psu so that I can really cook it.

-Matt
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Subjecting a nice 2" pancake to a long 12 year period of even infrequent measuring of many hot rocks where the screen almost, but does not touch the screen from above, has my lab NIM based GM have a rather permanent background of 250 cpm. As you can see, the GM tube is in a very short piece of 3-inch PNC pipe which can be raised or lower over a specimen. the NIM modules make up the counter where I feed to both a Ortec rate meter and then a Tennelec digital timer-scaler. I use this system more than any of my other instruments for detailed quantitative data. The hand held portable stuff is for sniffing around and remote work. I have a couple of spare LND 7311 pancake tubes. I think it is time to retire this one and that I-Hop to slip in a fresh pancake.

Richard Hull
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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 »

Richard,

Any idea if contaminated probes are actually damaged by having a spec constantly blasting it? I’m thinking about how lung tissue would react to having alpha particles bombard it 24/7. I think I’ll look at my probe under black light later to see if I can find the spec. Autunite is the most crumbly that I’ve used on it…

-Matt
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

I can't image a long bombardment of Alphas killing a mica windowed probe. I can imagine very much a background of 8,000cpm or more in such an instance of a virtual forever bombardment due to daughter attachments. The counting gas could suffer a bit but not likely, especially if no voltage is applied to shock the gas into counting via gas multiplication. (Assuming the probe is halogen quenched)

For the same recoil argument sticking daughter atoms to the mica, so goes the counter argument that those second daughters, in decaying to a third, might free the heavy, original parent heavy nucleus from the mica. I am sure it happens, but one should not let it happen at all.

I have no issues with sticking a hyper hot rock under the head in the images I included and dropping and locking the head in place with the screen 1-2mm from the specimen or item to be measured. I did put a copper screen on my homemade GM detector head. However, If it is hyper hot, I might only freeze the count at 30 sec and double the count as it is usually well over 20,000 counts in 30 seconds. Doubling that would not rip my statistically laissez-faire doubling to bits so far as accuracy of the count is concerned at the single sigma level.

Bill Kolb, my good friend, and even Carl Willis said to me, "You should not count the alphas as it gives a wrong impression on how hot the rock really is" I say, "What!!" It gives a full impression of how hot the rock is! Why own a superb 2" mica-windowed GM detector and not let it count the alphas??? Why did you buy a mica windowed detector in the first place if not to make it sensitive to alpha particle radiation? Sure, at 3-inches from the rock, there are no alphas, The betas can go out to a meter. The gamma's which are barely detected can leave the lab and go through the neighbor's dog! My retort is why not the alphas?

I think this mind set was out of some false sense of honesty to the average person or rock hound purchasing one of their ore specimens. Bill and Carl realize the average no-nothing, if he has a GM counter, it will be a yellow civil defense type or one of the ubiquitous $90 Russian tubed GM counters, both having solid metal envelopes that will never count alpha. If you count the alpha like I do, and say your ore sample counts 80k cpm and the no-nothings get 35 K with no Alpha, they might feel lied to. I have no such qualms as I report the full radiation. If they have a crummy detection setup, it ain't my fault, I was honest with them.

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 used to use a CDV700 to give my uranium ore readings on eBay. I saw that competition was using pancake probes and made mine look pitiful in comparison. That’s when I decided to get my Ludlum with the 44-9 :-) It definitely paid off…

Most of my rocks max out the cdv700 (shield open) and a few max it out shield closed, so I really needed something with a higher range anyways.

A few of my rocks almost max out the Ludlum.

I’ve found that some rocks are much more alpha rich than others, so I’d agree that alpha should be counted.
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Good man! Why understate a quantitative reality. Even and especially with the big 2-inch pancakes, missed counts kick in at a bit over 50,000 cpm and as I have specimens that actually count to 250,000 cpm with the pancake probe, can you imagine the losses and counts missed there! Good, reliable counting at that level is just out of the window. 250,000 cpm is stunningly under counted.

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 always felt that the more information, the better. I do make sure to give the details of the reads so the buyer knew that his cdv700 wasn’t going to have the same reading. My rocks always max those out anyways, so they were always happy!

Decided to do some more work towards getting my own psu working. I ordered a 3000w rms car amp that can go up to 30khz. That should be plenty of power and frequency response to not clip when running where I want to be. I’ll feed a signal generator into it to control voltage and current.

Also reworked my resistor divider board so that my 25uA meter reads 75kV at full scale. I figured 75kV is the max that I’m going to ever be able to do anytime soon. This will get bolted to some plexiglass along with the meter for voltage and a meter for current. It’s probably massive overkill but I’ve had it for years and glad to finally show it a good time.
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Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Time for an update!

Managed to get my multiplier + HF ferrite psu going. Pushed my little 20kV feed through up to 57kV before flashing it over pretty regularly so I splurged on a new 30kV feed through. This got me to near 65kV before I blew my multiplier. I’m now waiting on some capacitors to swap out the two that failed.

Before blowing things up, I was able to push things pretty hard compared to my Glassman. My highest run (that I believe is accurate) got me to 60mR/Hr on the Ludlum Priscilla. This was pushing near 60kV and 7-8mA at 12 microns.

My best silver activation got me to 2800cpm (up from 1200cpm): 55kV 10mA 12 microns for 2.5 mins.

I had to add some layers of lead sheet all around the chamber as the x rays began pouring out once I broke past 40kV.

Future updates planned:

1-Build a new 6 stage full wave multiplier so that I can push higher voltages and not fry my multiplier.
2-Better driver. Right now I’m using a function generator, car amp, and 12v 83A dc psu. The car amp gets extremely hot, so I know it’s not happy. I’ll probably go the Chinese zvs plus variac route before I finally build something using a PWM and half bridge. At least the car amp is the only thing getting hot, so it would seem the rest has plenty of Hp left.
3-More lead/better shielding.
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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

Really nice build. Very impressive results for a home build Voltage Multiplier. One of the more practical builds I've seen. I have a Chinese ZVS but have been able to reborrow the x-former I used before (Really wish they'd just sell it to me - not like they use it … .)

Really happy Fusor is back on line. A huge thanks to those that put in the massive effort to fix it!
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Thanks, Dennis. I’m striving to keep this clean and simple looking, easy to work on.

Placed my order for the 6 stage capacitors (47nF 6000v wima fkp1) a 1500VA toroid transformer (Hammond 117v primary and 60v secondary to use for isolation) and have another Fibox enclosure coming to house the 6 stage multiplier. I have a 1500w Chinese zvs sitting in a box already…

Hoping to melt my grid down with this “round 3” for the PSU. :-)
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Rich Feldman
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Re: Matt Gibson Fusor

Post by Rich Feldman »

Nice work there, Matt. Very inspiring for HV power supply enthusiasts.

Off topic: looks like fusor.net is back in business. Time to check recent admin posts, and spot check some very old posts & couple-years-old posts.
All models are wrong; some models are useful. -- George Box
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Credit goes to Steven Haid, Mark Rowley, and Finn Hammer…Either got parts from them, and/or inspiration from them. Happy to add another proof that this is the best way forward now that the 1ton X ray xfmrs are gone…
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Got the multiplier repaired. I had to use some 47nF capacitors as the 68nF ones are back ordered for months. It fired right back up…

But then as I tried to push beyond 50kV, I heard popping noises again. I shut down, discharged each capacitor (learned the painful way that they hold a charge despite shorting the bank out) and then probed around. Each capacitor measures exactly its rated capacitance and each diode tested good.

Bolted it all back together and pushed it up a little over 45kV. No popping noises, current draw was 15mA, pressure is around 12 microns. Only drawback is neutron output is only 20mR/hr at this voltage :-(

Decided to order a few more of the 47nF capacitors just in case…

Still waiting on my big order of capacitors to arrive so that I can start constructing the 6 stage full wave version of this. Hoping this will let me run at 75kV all day long without any failures.
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

I have a quick question that is bugging me:

Where is the optimal placement for the deuterium entry into the chamber? Right now, I have it entering from below, where the turbo connects. I’ve been thinking about redoing this such that it enters directly into the chamber (from the rear). Here is a picture of the setup:
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

At our vacuum level it is of little importance but I always locate my gas inlet port as far distant from the large vacuum port as possible. Like I say, we are in molecular flow mode and the gas let in is not subject to the early stages in pumping of viscous flow. The admitted gas molecules are moving faster than a rifle bullet individually with a long mean free path and will instantly disperse all over the chamber.

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 »

Hi Richard,

Thanks for the reply, I can put my efforts back towards my power supply:-)

Looking for any low hanging fruit…

Another question that I have: Should I re-do my cathode? It’s almost 1.5in and has to be forced through the openings into the chamber. I’m surprised it didn’t shatter when I swapped it to the new 30kV insulator. Would a smaller cathode help with output?

-Matt
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

No hard data exists here on cathode grid size. I would think the large the better just for dissipation's sake. You are lucky for after long use such grids suffer extreme hydrogen embrittlement and work hardening. I had a tantalum grid shatter after 2 years of use back in 2001 just due to a bit of rough handling while outside for inspection and gasket replacement and it was no tight squeeze like yours. Most all metals suffer hydrogen embrittlement to varying extents, and work hardening due to the constant long term expansion and contraction via thermal cycling.

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 was definitely in “fear and trepidation” mode trying to remove it:

I had installed an o-ring with stainless mesh screen in the bottom of the chamber flange connection to catch shards before they made their way deeper. I also bought more tungsten wire and stainless hypodermic tubing to make a new cathode.

I took a swig of scotch, pulled gently…It flexed, dragged through the flange, and then popped out. I then took another swig, and pushed it back in after changing the feed through and gasket.

Beginner luck or just not enough run time?
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

And so it begins! My 6 stage full wave multiplier is under way. I have to glue 36 of those capacitors to the board.

Each capacitor is a Wima fkp1, 6kV 47nF. Each stage will be rated for 12kV and 23.5nF.

This will be going into another Fibox container filled with oil.
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3 more stages to go, need the rest of my capacitors to be delivered (weeks out).
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Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Figured it’s time for an update:

Got the full wave 6 stage multiplier all finished up and did a few upgrades to the layout of everything. My best run to date resulted in a 5000cpm (up from 3400cpm) silver activation using a 44-9 pancake probe with my Ludlum.

The details of the run: 12.5 microns, 54kV, 11mA for just under a minute. The Ludlum PRESCILA “Hammer” probe face is 12.5in away from the center of the chamber. The run stayed in the high 3’smR/hr and regularly peaked over 4.6mR/hr. Going to let things cool down and see if I can maintain this for 3 minutes.

Edit: Final run before I go on vacation:
3’45” run
54-57kV
11mA
12.7-13.5 microns
5.4mR/hr peak

6200cpm silver activation.
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Great results! I see you recognize ways to improve what you have, constantly. I would imagine if you were to do another fusor from scratch, you have good ideas on how to do it easier and better. It is always the way with the learning and the doing. You see better ways of the doing from many lessons learned by the doing.

Have a great vacation.

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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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

Excellent run - all the effort and work paid off - you have activated silver. Do publish the details when you get back so Richard can add you to the Activation group.
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Thanks Dennis! I actually already made the list awhile back. This is just me pushing the gas pedal.

Richard, I’ve always got my eye on improvements. Next up will be a cube, a better driver (PWM and half bridge) for my PSU, and some remote operating capabilities.

Edit: Meant to ask earlier: I’m using a reversible fuel cell to produce my deuterium. I am noticing condensation forming in the tubing and syringe on a few occasions. It doesn’t seem to be hurting operation, but I imagine that it could be better. What’s causing this? Is it a problem with the membrane? Most of the time, it’s “dry”…

-Matt
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

A few upgrades are incoming and then a complete shift of gears.

Decided to get a 50L lecture bottle of deuterium on eBay as well as a Matheson 3320 pressure regulator for control. The pressure regulator is rated for 3000psi on the high pressure (tank) side and 100psi on the low side. My MFC likes to stay below 120psi, so this ought to work great for it.

Once that is working reliably, I’ll shift gears to a cube. I got a 5 way 3.38in conflat cube made my MDC on eBay. There shouldn’t be too much modifications needed to make this work with my current setup. Just need a few blanks and a 3.38” to 2.75” converter. It has two 2.75” conflat ports already….

-Matt
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Anyone have any somewhat simple ways to clear up solarized glass? I swapped out my viewport with a spare so I could clean up the original (it was getting pretty bad). Using a dremel, a polishing brush head, and some 15000 grit polishing compound, it came cleanish after a few minutes.

Here it is, post cleaning, solarized. It’s not a big deal, but if there’s a simple way to remove this, I might as well go for it. If not, oh well.
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