Matt Gibson Fusor

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John Futter
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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??
Matt_Gibson
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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
Matt_Gibson
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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
Matt_Gibson
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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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Rex Allers
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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
Matt_Gibson
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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
Matt_Gibson
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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
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

More Glassman frustrations today:

I decided to check the current meter vs the current monitoring output terminal (0-10v equals 0-15mA) and found it was off. I adjusted a trimpot and got the meter to closely match the monitoring output terminal.

I then checked the voltage meter and found it was spot on, so left it alone.

Now the problem:
At max voltage (-40kV), the psu kicks itself down to 3mA once I try to go beyond 6mA. It’s very deliberate and consistent so I’m guessing there’s some pesky circuit doing this. I’m not really great at reading 20+ year old schematics, just recognize a number of trimpots and op-amps, one of which, is probably my nemesis.

For a bit of sanity, I decided to plug this psu into my watt meter. Instead of seeing something in the realm of 250w (accounting for 14w of the fan and circuits running in the psu), I see I’m approaching 450w.

So now I’m completely confused at what is happening and what direction to take at this point. Who do I believe? The psu metering or my watt meter? Sadly, I didn’t work on any other dedicated metering because I planned to go off the Glassman metering.

-Matt
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

I would rely on the Glassman metering. You tuned it up. Go with it. Forget the external wattmeter.

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 »

At least I can put metering away then…

This leaves me with figuring out what on earth is causing the psu to buck the current each time I try to approach 6mA once I’m up beyond -30kV

Edit: Looks like the fun is over for now. PSU won’t even allow 1mA beyond 15kV. Instantly kicks it down and then completely out of I try to push it.

So now I’m at a crossroads. Do I spend $1k on an identical one on eBay that is in who knows what condition, and still needs to be converted to negative (what a pain that was) or do I attempt to build something that will probably burn the hell out of me :-)

Final edit: Decided to whip out my Dmm and test the VM. I found what I believe to be two bad diodes. I didn’t expect my meter to be able to test a HV diode, but low and behold, two of them in one of the final stages tests 0.6v forwards and backwards. I’ll replace these tomorrow and see if I’m back in business.
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Bob Reite
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Re: Matt Gibson Fusor

Post by Bob Reite »

An ordinary DMM will be able to detect a totally shorted diode, but not an open. Please refer to viewtopic.php?f=29&t=9549&p=64313#p64313 for how to test high voitage diodes, to which I will add that the military surplus ZM-11U bridge can also be used.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Bob,
Looks like you just beat me to it…I decided to move this back over to my Glassman psu thread in the new user chat section.

Just quickly, replacing the two diodes helped, but I’m still hunting for what I think will be some open circuit diodes. I’m going to cobble together a higher voltage psu later to test.
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Figured I’d start working on a new PSU in tandem with my current efforts to fix the Glassman. I already have a jumpstart:

4 stage, half wave, CW multiplier using wima fkp1 capacitors (2 in series for 12kV and 0.034uF). Diodes are 2CL2FM (20kV, 100mA, 100nS). I put this away after a quick test showed that it was awfully dangerous! Accidental discharges sound like gunfire. Multiplier is under oil.

Transformer is a high frequency ferrite on monster sized cores that I got from Steve Haid (a member here).

Resistor string came from years ago. 18 200Mohm 2w resistors. I’ll use this (probably remove/jumper some resistors based on what uA meter I can find) for voltage measurement. Current will be measured on the high side, suspended in air.

Per https://www.extremeelectronics.co.uk/ca ... alculator/, I should be able to push 20mA and have under 600v ripple. I’ll probably push these capacitors higher by 30% and still have thousands of hours of run time.

To do: I need a good driver that offers easy to control current and voltage. Probably some PWM IC and half/full bridge IGBTs or MOSFETS. Will also need a good isolation transformer (1500w toroid maybe?)
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Finn Hammer
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Re: Matt Gibson Fusor

Post by Finn Hammer »

Matt,
Looking as a good start, however:

Current is current, and it is the same everywhere in the circuit.
Can you give just one good reason for measuring it on the high side, when it can be measured as a voltage across a resistor in the ground leg of the multiplier?

Cheers, Finn Hammer
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Finn,

Trying to get wires in and out of the multiplier enclosure with oil and all seemed like a bother. I have a lightweight 100uA analog meter that “hangs” nicely in between my ballast resistor and my feed through toroid. Only drawback is that I can’t feed this into any sort of recorder or use something digital since it’s at high side, but that could be for later down the road.

Trying to measure current via the ground from my fusor chamber gave me a “0”. I think this is because I have multiple paths to ground due to me using a metal frame with multiple equipment that all have their own grounds?

Edit: Thinking it over, I may just fit a sense resistor in there for current, that way I’m not trying to eyeball things in multiple places :-)

-Matt
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Now!!! This is a real supply!!!! If this gets implemented, you are good to go! You have assembled the right stuff there. It has a good bit of ass behind it and it is ready to go to work. HF supplies are not the problem, it is the components often used in them. I would stick with 25khz and under. Those caps ought to be suitable filtering for even 10khz or less at the current you might need. Be careful! "You are not in Kansas any more"

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 »

Thanks, Richard!

I think I’m going to try to fit the HF transformer in with the multiplier so that it’s all under oil…Just need to get a bigger box and more gallons of mineral oil. Tractor Supply already thought that I had one sick horse after I bought several gallons before…

Gonna get some G10 boards on order to start mounting stuff to.

While I work out the driver details, I’ll go back to using a car amp and signal generator for testing. I blew up the last one…

Still not giving up on my little Glassman. I’m bound and determined to make it work for Silver activation and keep me satisfied until I can get this big boy going…Got to get my daily fix in now that I got a taste!
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