Matt Gibson Fusor

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Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

I’ll go the MFC route…I have been trying to keep ease of operation in mind over simplicity and cost. I quickly lose interest in a project if I have to hassle with it too much :-)

Any really good brands to look for other than MKS?

I’m going to hook my grounds and psu this weekend. Hoping for a plasma club entry soon.
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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

MKS are excellent flow control devices. I've used them in the past with great success. But in buying any flow controller be aware they come in many flow volumes so get the right one. Besides the actual flow control unit, some require a separate power and readout display is also required. These devices have various connector options so if you use swagelok get that type.

New flow controllers are not cheap. Consider a good quality manual valve flow control valve for deuterium gas. These work very well (Yes, manual) and might be a good option, too.
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Finn Hammer
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Re: Matt Gibson Fusor

Post by Finn Hammer »

Trying your luck with making an offer on this unit might be a good idea.
Factory refurbished is the way to go with this kind of hardware, which is impossible to fix, for the average joe, if broken.
https://www.ebay.com/itm/304230386834?h ... SwHXlhlrcb
It is a helium calibration, but it should still work ok with H2.
You will need a + -15V supply to power it, a panel meter readout to read it, preferably with floating meter unit, we have been talking about them in another thread just the other day, and a 5-10 turn pot to controll it.

Good luck,

Cheers, Finn Hammer
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Finn,

Looks like we’re thinking the same wavelength. Here is one I placed a bid on:

https://www.ebay.com/itm/MKS-Instrument ... 632-2357-0
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Alright! First plasma (no deuterium).

Strikes at 30kV (on fusor meter) and 5.5 microns. Immediately drops to 10kV and pressure climbing quickly.

So I’m confused here. The meter that I have connected from ballast resistor to ground shows 30kV but my PSU meter shows 34kv-ish. How can there be this much voltage drop? I’m using RG213 (3ft) as my HV wiring.

On the positive note, no sparking on the inside or the outside despite me putting 30kV+ on a 20kV insulator.

Edit: My Ludlum 3 with pancake probe starts screaming at 22kV (fusor) and almost maxes out at 30kV. This is about 2’ from the viewport. Time to get some shields in order.
061E8ED4-E926-44A5-B48A-B8D8EA8890B5.jpeg
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Not a word about your current!!! Why bother reporting anything and then ask questions when you refuse to give all data. you gave two voltages, pressure and other details. Current is key!!! Why not multiply your current times your ballast resistor value and see what the answer is?? Data! Data! data! All of it!

I tell everyone all the time that at about 20kv a viewport will scream with nasty flesh burning x-rays. These x-rays are easily stopped dead in their tracks.

After my many FAQs dealing with construction, I can't understand why folks insist on pointing the viewport right at their gonads, or chests or much worse, at face level. The most sensitive organ in the body to radiation is the eye. Point all view ports to an outside wall or at the floor or anywhere where people aren't! View by point contact with a wide angle video camera or a less useful, mirror-telescope arrangement.

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, 3mA. Even down to less than 1mA, or as high as 10mA, the voltage at the ballast (50kOhms) is roughly 4kV less than the PSU meter shows. There shouldn’t be more than a few hundred volts dropped across the ballast…Something else seems off?

Edit: As for the X-rays, I’m off to the side when operating. I held the probe such that the head was in line of sight of the viewport. Same with the camera for the picture.
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

I would suspect inaccuracies in the homemade voltmeter at the wire going to the fusor. How did you calibrate it. Such HV meters need to be calibrated using an accurate source %5 accuracy in 100 meg resistors will be in tolerance at 95 and 105 megohms. Four or five in series could be far out of tolerance to 10% or more so calculation could easily seem good but at 35kv could easily be 3-5Kv in error. You need to trim the string into correct reading using an accurately known source.

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 »

Am I being needlessly redundant by having a second volt meter here? My max current from the psu is 15mA…That’s 750v dropped across the ballast if I ignore the resistance of the Hv wire to the fusor…Any reason NOT to go by the psu meter only?
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

That is fine +/- 500 volts is nothing at 35kv. Close enough for government work, as we use to say in the fusion biz.

If you lust for accuracy make up a little cheat sheet chart from 5 ma to 15ma with calculated drops for each current in your ballast and subtract the fusor operating current drop from you PSU meter reading. A much more accurate voltage to report.

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 »

Worry more about shielding rather then typical voltage drops; having your meter hitting high values (scale?) on the Geiger counter is not good with no shielding (yes, it is a sensitive pancake probe.) Standing off to the side assumes that only the view port is the sole dangerous radiation source. That might not be the case as your voltage climbs above 30 kV.

I warned you about that issue - especially the window. I would think suspending plasma's until proper shielding is installed would be a safe approach for now.

By the way, your local home depot hardware store carries very inexpensive slate 'tiles' and at 1/4 the density of lead so it would be easy to create good shielding quickly. Slate is very easy to drill or cut with proper dry bits/blades (inexpensive), as needed. Could get it done today while you wait for lead sheet you ordered if you go that route.

I posted a photo of my fusor with title plates as shielding and, of course, my view port pointed away from me. I use a mirror to see inside the fusor. A very simple but extremely effective methodology to deal with view port radiation.

Your pressure and voltage agree well with my results from my first fusor (though, I had to replace that TC gauge - in fusor 'three' it gives absurd results.).

By the way, this post makes you a candidate for the Plasma club, I would think? You should request that from Richard.


Aside: Thread that has pic's of my fusor - note shielding system and lower body protection lead sheet besides central tile shielding system. Also note mirror system for the view port: viewtopic.php?f=6&t=14261&start=10
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Richard,

I’ll stick with the Glassman meter and ditch the 100uA meter. Much easier/cleaner that way.

Dennis,

I’ll bolt a few tiles into the rig to help in conjunction with the lead sheeting that I plan to wrap around the various parts of the chamber.

The scale goes to 660kcpm (alpha, beta, and gamma). The reading was taken from the exposed side of probe. From the back side (shielded), the reads dropped dramatically. It was a hasty reading as I wasn’t too excited having my hand close to the setup as is. From the side, the readings were pretty minimal.

This was more of a test of the psu and the standoff, so data/results are crude. Once I have some shielding in place and a better way to view the plasma (mirror or webcam) I’ll get back on it. Plus, I need to open up the psu to see why the multiplier stack is stinking so much (smells like an old computer running).

-Matt
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Turns out I had a bit of 1/16” lead left over from shipping some ultra hot uraninite to Japan :-)

I ghetto laminated (spray on enamel and then scotch tape) the lead sheet to cut out lead dust and then went to work forming it around my viewport. Added another beam to mount a mirror or webcam in front.

How’s it look? Getting closer?

As a “test”, I placed a piece of hot uraninite inside. Before it reads 440kcpm and afterwards, 50kcpm.
487F1DB5-14E2-483F-8D5E-CAC97CFC5C57.jpeg
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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

Looks good; do keep the voltage down till you get the rest of the shielding in place. Below 30 kV the steel should be able to stop a lot of the x-rays.
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Any value in adding some lead glass?

Edit: Won the MKS GM50A (10sccm), no thanks to a random bidder, so will hope to use this for the deuterium.
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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

Well, stopping x-rays from any direction can be worthwhile but whether to do this is mainly up to you. I certainly haven't nor will I on mine since it is pointed away from me and I won't have any reason to get in front of it while running. But placing a leaded glass plate over the existing vacuum window would be trivially easy and add an extra element of safety.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

I picked up one (used on eBay) that is supposed to be the equivalent to 2.5mm of lead.
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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

As the saying goes* - when it comes to radiation safety: don't trust but do verify for your self!

*Ok, I made this up.
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Oh I’ll definitely stick my probe out before I step out…

The only other thing that has maxed out my 44-9 probe is a radium gauge from a Ukrainian (or maybe it’s Russian?) Geiger counter. These were known to have freakishly high amounts of radium paint. It lives in a plastic bag inside of a lead pig.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Plasma club submission and update:

Got my x ray lead glass installed …It was supposed to come from Ukraine but came from a USA address and only took a few days! I used some optical glue to glue to a 2.75” conflat blank and stuck it into place.

X rays before glass: 660kcpm (max for my meter) on my Ludlum 3 with 44-9 probe. Afterwards, background (varies around 100cpm).

Plasma club submission:13.3 microns, 24kV, 3mA.
04FD92E0-36DB-4673-AB89-1E53FF9C657F.jpeg
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Matt, you are in the plasma club. Good work.

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! Shouldn’t be much longer now…Need to get my MKS MFC online/tweaked and then make some deuterium via fuel cell.
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Another update:

Got my MKS MFC (GM50A 10SCCM). It booted up and I was able to open/close valve. Because Apple hates Ethernet connections, this is the extent of the testing that I can do until I get my work laptop next week (can’t believe I forgot to take it home). I was hoping to get it synced up to my Pirani for auto pressure control…

The MFC looks to be completely unused. I don’t even see marks where it would have been mounted. Not sure how these things wind up on eBay for so cheap?

Here is the deuterium section so far:
E4928874-6C17-4234-AB49-202E6D3B7661.jpeg
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Update!

I finally had a few runs with deuterium…I am using one of those Ludlum 2363 with the PRESCILA probe for detection, 1.5in away from the chamber.
097F704D-3803-4AAA-AF7E-385605B96D21.jpeg
Background count: 5.2cpm
Run time with deuterium: 6.5mins
Voltage and Current: 39kv, 7mA
Pressure: 10.7microns
Deuterium flow rate: 0.8sccm

I was able to achieve 100cpm with deuterium. The chamber got up to around 220F (IR thermometer) before I powered down.

It’s been said that this could just be electrical noise. Being that this probe and detector are new to the fusor scene, here I am asking how to interpret my results.
FFD8BD83-3A0D-42ED-8DF1-A4EB322267CA.jpeg
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

I do not know how to respond. With the data you give, you should have recorded thousands of CPM.

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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