Matt Gibson Fusor

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Matt_Gibson
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Matt Gibson Fusor

Post by Matt_Gibson »

Hi everyone, figured I’d start my own build…

Here is my current setup. I am waiting on gaskets and hardware to start sealing everything up…

Pictured is the start of the fusor project. Specs so far:
Foreline pump: Edwards e2m2
Turbo pump: Pfieffer TMH 071p (not shown)
PSU: Glassman 40kV @ 15mA (I converted it to negative)
Chamber: 4 way cross, 6in by 2.75in.

Deuterium: Reversible PEM fuel cell and SGE glass 100mL syringe.

As I test, acquire, I’ll take better pictures and give more details.

Let me know if anything stands out as problematic, please! :-)

-Matt
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

Nice looking rig. All the best in doing fusion in future.

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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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

Curious, why the large metal torus on the high voltage feed=thru?

Also, what is the unit on top of the power supply?

Good start on your build. Are you going to add a manual gate valve for the pump connection to the fusor?
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

The toroid is to cut down on any corona discharge from the -40kV. The feed through is rated for 20kV, so I’m hoping this lets it get to 40kv…

The box on top of the Hv psu is a 100kV, 1mA multiplier from Glassman. It isn’t part of this system (yet) just needed a place to rest (running out of space).

I have three valves total. One will be for the fusor chamber, another for the foreline, and the third for the deuterium feed from the 100mL syringe.

UPS didn’t make it, so I won’t be able to hook up the turbo to the e2m2 until next week sometime. Once I confirm that the turbo spins up under proper vacuum, I’ll begin bolting everything up and then it’s full steam ahead :-)
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

You might try raising that toroid up a bit. A healthy fan blowing horizontally over, across the insulator at about 1 to 1.5 feet will served to whisk away coronal ions which might support an arc rising due to natural heat convection. This summer I used a huge box fan on high at a range of 6 feet to do the job. It worked wonders....Zero arcs.. and in my hot lab keeps me cool as well.

Richard Hull
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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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Re: Matt Gibson Fusor

Post by Matt_Gibson »

I’m hopeful that this extra bit of field control works at 40kV. If not, I’ll see about getting it raised up. A fan will probably get mounted on the rig no matter what as I expect this thing to get hot seeing as I have 600w at my disposal :-)
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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

A toroid might help but if it was me, I'd remove that toroid and simply buy a few sheets of window glass (squares are fine, 8" x 8".) Next, cut clearance holes through the plates (excellent and inexpensive diamond hole saws can be obtained on line). Cut the holes so they can just permit the upper part of the ceramic stand-off tower to pass through these holes. The plates can then rest on the first ceramic "fin". These plates will then stand between the fusor and the top most part of the HV metal electrode. Then add a good thick silicon bead around the ceramic/glass plate interface opening to further insulate and hold the plates in place. This will prevent arc over to the fusor from the HV tip. The toroid could still be put back in place if you desired. An idea just in case the toroid does fail.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Dennis, I’ll keep that in mind.

I am leaning towards going with the 30kV insulator that everyone seems to be having success with. I am worried that my internal clearance may not be enough. Here is the shot of its underside. The alumina tube doesn’t extend very far…

This leads me to another design choice: To ballast or not. My glassman has overcurrent protection built in, but I don’t know just how “fast” it is or how well it works compared to a ballast resistor.
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Re: Matt Gibson Fusor

Post by Liam David »

I don't think you'll have issues with the shorter vacuum-side alumina at 40kV, but that does depend strongly on how you interface the feedthrough with the grid (i.e. alumina stalk vs. not, geometry, how centered your conductor is, cleanliness, etc...).

I'd recommend at least starting with a ballast resistor. You'll lose a little voltage but plasmas can be punishing to power supplies, especially when the discharge first establishes.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Finally was able to test the turbo.

Turbo went below what my Pirani can measure and rpm went to max of 90,000 (10v is max rpm).

Getting closer!

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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

As for the lack of ceramic extension into the vacuum system, that isn't as bad as you might suspect - the plasma is both very conductive (over a volume) but has limits in any given small volume at low pressure (under 100 microns); so it is partly self limiting in the normal vacuum range that a fusor operates: 5 -20c microns. All bets off if you go a good bit above that pressure. Then the plasma can focus and support a considerable current. and at near torr range, support an arc.

If your worried, adding a glass tube extension that fits inside the ceramic tube and affixed with some furnace grade ceramic adhesive should work to insulate the rod.

Your turbo had better zero out a micron gauge for your system; an ionization or cold cathode will be required to determine the lowest value. Anything in the mid 10^-5 torr is good for a fusor as "clean" and vacuum tight.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

So I think that I might have a leak…The new bspp to Kf25 flange didn’t come with an o-ring, so I took one off another fitting. This definitely helped things as before (no o-ring) I was pulling in the Torrs. After this improvised o-ring, it pulls into the mTorr, but now only gets down to 45mTorr after 10mins.

I’m guessing that while the o-ring helped, it’s needing something better. What else can I do? Better o-ring? Teflon tape on the bspp threads?

As of now, I’ve added a 8.5in length of steel tubing (Kf25 ends) and the turbo. I know that I shouldn’t expect the same performance as before these additions, but I expected better.

I have yet to hook up the chamber, so I’m expecting worse after that.
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Re: Matt Gibson Fusor

Post by Richard Hull »

Every addition to a piecemeal tested vacuum system will suffer a reduction in performance due to any number of factors. Most often it is something stupid, poor sealing, ill suited additions, etc. The number one issue is that you brought you entire system up to air. Even with valves to close off a tested, partially assembled vacuum system, the new part will be loaded with all manner of water vapor and other vaporous materials that will either require many hours of system pumping or a tedious bake out to bring to a suitable vacuum level.

You are wise in following my vacuum system advice to assemble and test a system step by step. In this manner, you are confident in all the work done up to a point. (Seals are good and the system thus far assembled is good.) Each new addition imposes a trial period of sealing and pumping.

If you get a great idea and go back into the already tested system to add something great like a valve or a new fitting, you fight the battle all over again. Without a whole bunch of heat tape to bake out with, you are subject to long pumping periods and a lot of leak testing. Even technical vacuums can be frustrating to achieve. Scientific grade vacuum levels demand a special level of cleanliness. A good scientific level vacuum system, especially a complex one, is just never brought back up to air unless it is absolutely unavoidable. Such systems are loaded with top grade and expensive valving all along the vacuum path and all pumps are left on 24-7.

A good fusor needs a minimum of three vacuum valves, though two bellows seal valves will do in some cases. The fusor is trapped between a technical and scientific vacuum. Technical vacuum levels, (10 microns), just will not cut it and scientific level vacuums, (10e-6 torr), while nice, are just ridiculous over kill.

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.
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Richard,

I have a valve meant to isolate the turbo from the foreline pump, just waiting on more Kf25 clamps :-)

I removed the turbo from the system and found that I can quickly (20 seconds or so) hit 12 microns at the end of the 8.5in steel tubing. I gave the bspp to Kf25 fitting a tighter twist and then reconnected the turbo to the system. It’s better (38 microns after 10 mins) but still not great.

Would this point you towards a better bspp to Kf25 seal?

All in all, the turbo is still able to rapidly drop to “zero” microns, I just can’t stand knowing something can be improved :-)
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

Don't over react to out gassing. What you describe sounds a lot like it. Don't assume a slow leak automatically. Just a minor aside, we tend to use microns here to be consentient.

When you can read below 10^-3 torr (using a vacuum gauge for those lower ranges), you can do real testing for small leaks and certainly determine if it is just out gassing or not.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Dennis,

Got my units mixed up after looking at the Pirani so much lately…

I looked back at MTI site and see they sell a gasket meant to go with this converter. They didn’t include it, or make any mention of it. Despite it weighing like a gram, they want $23 to ship it. I’ll see what McMaster has.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Update:

Finally got my system bolted together and did some initial testing.

I am pretty limited in what I can determine right now because I don’t have any high vacuum gauges (any recommendations?). I have the Lesker Pirani and the MKS901 (needs to be installed still).

I am able to get to 0.1 microns (the limit for the Lesker Pirani) in under 10 mins (I need to actually time this). After 10 hours, my pressure creeps up to 252 microns. I tried spraying dust off into each and every connection point to see if it caused any jump in pressure, but it didn’t.

Haven’t done any baking…Would this pressure rise indicate moisture and not leaking?

Edit: Should add that there are a lot of loose ends and work to be done :-) I know I need to add an alumina tube to my feed through and some space on the main valve to the chamber, for example. Not thrilled having my hands so close to the frame, grounded or not.
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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

First off, very professional looking system.

Second, searching for a real leak when your system climbs just 250 microns in 10 hours is an utter waste of time; that isn't a leak at all - that is very little out gassing from a rather clean system. Baking would be of little value.

Your getting 0.1 micron (1 * 10^-4 torr, bottom of the reading) so are more then likely getting to 10^-5 torr and sufficient for a fusor (starting pressure.) Considering how very clean your system is and the gauge reading to 0.1 micron (bottomed out - likely much lower), you really don't need to measure below that value if you don't want to add another gauge/system. Again, you are essentially there.

If your power supply goes above 30 kV, that steel chamber can start to become dangerously transparent to x-rays; that window -depending on thickness/type of glass - could be a significant x-ray source even at 30 kV. Consider shielding if you determine these parts can't stop the x-rays. To be on the safe side, assume they will and just add sufficient extra shielding. Slate tiles would work nicely.

Remember, x-rays will travel 4Pi steradians so coverage below the fusor is important too - i.e. your lower body will be exposed in that setup too without proper shielding. Think of the fusor as a light bulb (ignore the metal) and that is where the x-rays go. That determines your shielding areas - the threat areas are places that you would be exposed by the 'light' (no shielding) when operating or working around a running system.

So, it looks to me that beside shielding, you just need deuterium and a neutron detection system and you could start doing fusion.
Last edited by Dennis P Brown on Fri Dec 10, 2021 1:47 pm, edited 1 time in total.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Dennis,

Good to know the system is clean! I spent some time wiping down as much as I could (pretty much everything minus the turbo innards) with 99.9% isopropyl alcohol and handled everything with cotton gloves.

I was a tad worried that my chamber was a bit large for my relatively small roughing pump, but it seems like it’s fine actually.

My psu can go to 40kV @ 15mA, so X-rays are definitely a concern. The viewport is a Lesker Kodial glass type, which I don’t know much about…I’ll probably find some leaded glass to put on the outside. I’ll use my Ludlum to sniff out X-rays very early on so that I can avoid them.

-Matt
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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

Your entire fusor could be transparent to x-rays at 40 kV and significant current. You might very well require extra shielding. Just look up penetration depths of x-rays @ 40 kV and you'll know if the steel case can stop that energy. Unlikely the view port glass will but again, look up the values for those energy x-rays.
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Re: Matt Gibson Fusor

Post by Richard Hull »

A GM counter will scream at the viewport often before 20kv. It is the real danger for X-rays. A proper calibrated ion chamber will tell all about X-rays. Barring a proper ion chamber instrument. A good group of 3 dosimeters placed next to the fusor and at various ranges from the fusor will tell of total dose. Use only 100mr dosimeters. The yellow CD types are to read max doses of 600R! (Use the yellow dosimeters only after a total, world-wide, nuclear exchange as you venture out in the smoking rubble.)

My 100mr dosimeters read about 10mr when 1/2-inch from the fusor after about 1 hour of fiddling and doing fusion. At 2 feet, just off zero and in my shirt pocket 5 feet away, zero. This readings are taken at 40kv+
I shield only the viewport area very well with 1/8-inch lead. The fusor, I leave naked and unshielded.

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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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Richard,

Thanks for the tips! I’ll admit, physics wasn’t my strongest in college (I did electrical engineering and focused on power), so I’ve been wracking my brain trying to look for x ray penetration formulas!

I’ll grab some lead next time I order from McMaster (I bet they love me by now) to fix around the viewport.

Speaking of deuterium…I plan to use a 100mL syringe made for gases to capture the deuterium production from a fuel cell. I need a way to regulate the gas into the chamber still…Other than a bellows valve that I have installed, do I need to worry myself with needle valves or MFC’s?

Thanks!
Matt
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Richard Hull
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Re: Matt Gibson Fusor

Post by Richard Hull »

When it come to lead sheeting try Rotometals.com. They have a full x-ray penetration chart and shopping page at the URL below. I see 1/16-inch thick should do you, but I would opt for a bit thicker. 1 foot square sheet of 1/16" is $23. (1/8" is $36 is Overkill). The issue with all metals is that sheet and wire are the most expensive forms of any metal and often command prices 5-20X the market price of bulk metal ingot. Lead is currently just over $1.00/lb on the market at 1000lb lots. The 1/8" square foot is 8 lbs. 36/8 = 4.5X. This is because lead is easy to work.

https://www.rotometals.com/lead-sheet-plates/

They are listed in the primary sources for any and all metals. I rarely have to order metals, but I always find them my best buy in small quantities from 8 ounces up to 100 lbs of metal, especially in rare or oddball metallic elements. Use the primary source forum.

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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
Retired now...Doing only what I want and not what I should...every day is a saturday.
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Dennis P Brown
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

To control deuterium into a fusor a 'leak' valve of some type is absolutely essential - standard vacuum valves (like bellows) simply do not offer enough control. A leak valve can be made or bought. High quality leak control valves are expensive even compared to vacuum valves but are available from vacuum supply companies. Making a valve that can perform in a somewhat similar manner has been done by people here. If I recall correctly they use a type of fairly inexpensive needle valve (AC grade) and add a very small capillary tube; one could also use a special micro-pin hole (companies make these for the medical industry applications.) Search the Fusor construction FAQ for leak valves - I believe that topic is covered there.
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Re: Matt Gibson Fusor

Post by Finn Hammer »

An MFC is the gold standard of flow control.
I use one of the 10CCM variety, and it gives superiour controll of the flow, and thus the fusor pressure, which can easily be regulated to less than a microns presicion.
Get one, you won't regret it if you do.
And if you should ever contemplate to create an autotuning fusor, you will need one anyway.....

Cheers, Finn hammer
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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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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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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
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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
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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.
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Re: Matt Gibson Fusor

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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.

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Fusion is the energy of the future....and it always will be
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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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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
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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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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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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
Retired now...Doing only what I want and not what I should...every day is a saturday.
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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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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.
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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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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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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.
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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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Post by Richard Hull »

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

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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.
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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
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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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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.

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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Richard,

I think that this detector actually measures in mR/hr with a conversion of 350cpm/1mR/hr. I used the Matlab code provided in the thread dedicated to these detectors to generate the background and the run with deuterium.

Looking at the raw data, many 1/2second hits were over 2mR/hr.

Maybe the actual CPM should be 100*350?

Edit: Here is a graph of the data
1_1_22_run1.jpg
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Re: Matt Gibson Fusor

Post by Richard Hull »

Matt, I tend to agree with you here. Others who read this please chime in I think 35,000 CPM is within reason for the stated run data and I think I fully understand Matt's logic and reduction here.

If other users of this specific counter system agree, I will put Matt in the neutron club. Matt, You need to grab some pure silver, slap it in a moderator and a GM counter, if this is real.

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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Hi Richard,

I have some 999 silver sheet left over from my ruby laser project, guess that ought to work? As for a moderator, I don’t have anything handy. Where is everyone getting their HDPE from? Would two 1” pieces of HDPE be sufficient for activation?

-Matt
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Re: Matt Gibson Fusor

Post by Joe Gayo »

Are you using Andrew S.'s code as is? I think he may already be converting the mrem value to counts.

I'm also surprised by the 0.5 sec intervals with no measured counts.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

I am using Andrew’s code…

There were a few instances where the plasma went out while I was playing with the pressure, maybe that’s the cause of the zero counts?
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Update:

I’ve been playing with the deuterium flow rate and found that cranking it up and opening the chamber valve (to maintain a pressure in the 14micron range) more than doubled the reading.

Before, I was hitting over 2mR/hr on the meter. Now I am hitting over 5mR/hr. Using Andrew’s Matlab code, I am getting a CPM value of 183 (up from 114).

So how do I rule out x rays and noise? Should I split some de-ionized water and run hydrogen to see if I still get readings?

Not sure how to interpret what I am seeing…Neutrons? If so, what do these readings actually translate to? I am maxing out at 39/40kV at 7mA and around 14 microns. Not sure how to get my current draw up. My psu can go to 15mA.

Maybe I need to dry my deuterium?
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Update:

Some more playing around. This time, I hit over 8mR/Hr (Ludlum value) a few times. This occurred at 40kV@7mA and 15.2 microns. In order to achieve this combo, I have to have my system running at full tilt (Deuterium flowing at 10sccm and chamber valve full open with the turbo going at 100%).

Here is a graph of the raw data from the Ludlum. X-axis is time in 1/2 seconds and Y-axis is mR/Hr from the Ludlum. You can see me adjusting/fidgeting with the Deuterium flow and the chamber valve. As I crank up the Deuterium, the mR/Hr drops and then gradually climbs again. The large drop in mR/Hr occurred when I just decided to go for broke and janked it up to 10sccm (Max flow). Run time was a little over 16 mins. At this point, the Ludlum is sounding irate…If not neutrons, what could all of this be?

I have some HDPE coming...Hopefully I'll be able to active some silver and then call this a success?


Best_Run.pdf
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Re: Matt Gibson Fusor

Post by Richard Hull »

Matt,
What you are measuring are 100% neutrons! Welcome to the neutron club! I will log you in. These Ludlums have proven themselves in reports here and your results are so close to mine that they could only be neutrons you are seeing! Read my report of my run on the same date as you ran your system and my comparison of our results, bolstering my variability FAQ in the neutron and radiation forum.

I hope this is not comparing apples and oranges. I run a sphere. I am back in the biz to compare various methods of measuring and I am happy to say that within 10% or more they all agree. I post here as the conditions are similar in some ways to Matt's work with a totally different measuring scheme. I was amazed at the close similarities of our results, considering the difference in devices and methods of measurement.

I will add a modified, combined reply relating Matt's reply above and my own here to my FAQ on the variability of fusion rate in a fusor in the neutron and radiation forum FAQ I recently posted.

I now have my Rem ball and my PNC-1 working along with my normal 3He detector.

Last night's run topped out at a bit over 500k n/s based on the 3He calibration. I activated Rhodium to 22 times background (background here is about 4 times most folks GM background) both the mrem/hr reading of the Rem ball and the PNC-1 block moderators were varying over 10 second intervals, up and down as noted in other recent postings by me. This matched Matt's wild second based insane variations and his more moderate time averaged variations. My analog variations, (real time needle swings), were on the order of his moderated average variations in mrem/hr.

My Data: 41kv, 11ma, 10microns D2,....At this operating point PNC-1: 6.8 - 7.4 mrem/hr.....Rem ball/PNR-4 lin-log reading: 6.6 - 7.8 mrem/hr....Both the ball and the PNC-1 block moderators jammed against the fusor. 3He count was 86,205 cpm (translates to over 517,000 n/s TIER).... Rhodium peak activation was ~1300cpm (rhodium's very small surface area foil exposed 2pi to GM tube = ~6 sq cm).

1. I have to believe Matt is doing fusion and that his posted reduction above proves my point that all fusors are not steady fusing entities but have, on the micro time scale, immense fusion output differentials. (Matt's and other's data)....New Ludlum micro dose delivery detectors.
2. However, when analog averaged over10-20 seconds, a net emission of fusion neutrons swings about a common point +/-10%.....(Remball/PNC-1)
3. One full minute hard digital counts can vary about +/-2%.... (3He).
Activation over time and bubble dosimeters would be the pure net emission or dose total indicator.

As noted before and stated in my FAQ....

The fusor due to its simplicity with many modalities with cross interference between them is not a steady fusioning system on extremely small time scales but over a number of minutes can be reduced to a reliable net dose device if all of the parameters in its operation are held steady. Even a morass of confused emission with steady parameters feeding it will , by statistical analysis over time, settle into a usable average emission rate and TIER, in our case.

Note: all of this valuable neutron radiation data on this new Ludlum system should never appear in images du jour or in the construction forums. It belongs in the neutron and radiation forum... Oh well, we do let such things smoothly flow from one thing to another, quite innocently I might add. I hope all this good stuff related to neutron counting and measurement is not lost in future buried hopelessly in the images forum here. It is for this reason that I will edit this into the neutron variability FAQ post as a reply...

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Re: Matt Gibson Fusor

Post by Finn Hammer »

As promised, here are data from my cube, as recorded with the Ludlum 2363, at 40kV, 7mA, same as Matt's fusion claim run.
It will be noted that the cube reaches higher numbers than Matt's fusor does, but then the pressure is also so much higher, 28 microns as opposed to Matt's 15.

Parameters at running time
Parameters at running time

Here are the recorded numbers, from the first 10 minutes of a 13 minutes run:

Matt1.JPG

Doing a bit of calc on the numbers: there is an average of 25mRem/hour multiplied by 350 gives 8750 cpm. Divided by 5670 to get "x"e5n/s, gives 1.54e5n/s
I recorded the activation result with silver, 45kcpm, as seen on this short video clip:

EDIT!!! The cpm recorded was 4.5kcpm, I got the multiplier setting wrong.


https://youtu.be/9d-5uwQ-caA


Matt, welcome in the neutron club!

Cheers, Finn Hammer
Last edited by Finn Hammer on Tue Jan 04, 2022 4:58 am, edited 2 times in total.
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Re: Matt Gibson Fusor

Post by Richard Hull »

Nearly double the fusion fuel in a smaller chamber that is known to do significant BOT via concentrated end plate wall loading and you are doing about three times more fusion. I believe it.

I also believe you are doing far over a mega fusions/second at this level. If you get the bubble detectors I think you will find this to be the case.

I see it is now almost 5AM in the morning....Now out to the lab for a fusion run, then back into the house for bed time at about 7AM.

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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
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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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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.

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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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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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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.

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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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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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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
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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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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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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
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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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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
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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.
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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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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.

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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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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..

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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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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.

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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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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.
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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.
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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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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
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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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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"

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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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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Is there any reason to submerge the entire transformer in oil vs just it’s secondary side? If not, I’d have the primary sticking up and out of the oil. This would let me use a shallower box and less oil :-)
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Re: Matt Gibson Fusor

Post by Richard Hull »

An odd question to all but the inventive and impoverished. Sure! Dunk the nasty end of the thing. The low voltage end may rise above the waves. Make sure to send a photo of this curiosity for all to enjoy.

Odd looking things can be flawlessly functional but induce a bit of humor to those use to specific methodologies.

A true story:

I started the Richmond Robotics Group back in 1982. In those days you took a 6502 @ 1mhz, added an EPROM, about 4 k of memory and the 6522, its' peripheral port IC. This was to make an assembly language based micro controller for your robot. Most of us were used to point to point wire wrap and would choose a suitable length of wire and wrap to the IC sockets in a nice flush manner routing the wires not directly, but in a serviceable manner around the bottom of the PC board. Needless to say, this hand-work produced well over 200 individual connections and 100 or more wires from about 2-40 pin chips, 3-24 pin chips and about 7-16pin chips. The wire layout was confused but very neat and laid flat along the bottom of the board, often held in, well routed and flat bundles with a dab of glue once the board proved itself working. They were works of wire wrap art. A just and well deserved pride in such efforts were well received.

One of our non-electronic members also made a board that worked great, but used all precut 4" wires that he bought to avoid the hundreds of precise wire cuttings and strippings needed as the rest of us had struggled through as a love's labor. He came to a monthly meeting with his functional pride and joy. The moment he presented it from within the box in which he had brought it, laughter erupted from every member of the group, tears of mirth ran down the cheeks of the hyper amused. He presented his board with a perfectly symmetrical hemisphere of about a 3-inch radius done in a myriad of blue 4-inch wire wrap wires. A board atop a 6 inch diameter hemisphere of insanely close, knotted wires. Comments like... "Light will not penetrate it!".... "Only a wire wrapping spider could do that!".... and "Where is the socket for that ball joint?", were elicited. It was a marvel to behold! Reference to it was made all throughout the meeting. How one would mount such a finished processor board also was a topic of discussion into hyperbole with more mirth.

Alas, upon leaving that meeting, the poor guy never returned. We were laughing, not at him, but his unusual creation born out of a work-around to save time and use pre-cut and stripped fixed length wire. Sometimes we are all laughed at for what we say or do. The key is to learn when the laughter is directed out of friendship and in the spirit of the moment and not as a derisive shame upon you, as a person, by a mean spirited person or persons. Learn to laugh at yourself. Enjoy life. Thin-skins are not the ticket for engineering or scientific teams for at some point, everyone is laughed at or found in a faux pas.

The lesson is something functional may look odd and elicit some humorous comments from your peers, but do not let it bother you if it works.

Richard Hull
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Richard, you should have seen how I constructed my projects during HS and college! Functional, but ugly…

I tend to ease into something and then improve it as I succeed.

A good example of funny looking but working is my 20kV feed through sporting a “top hat”. The 20kV feed through was on eBay for less than half the price of a 30kV one…Looks funny but I haven’t had a single arc over nor do I see any corona discharge (lights off) at 40kV.

I’ll definitely take plenty of pictures as I progress! Going to put a bit of work into form as well as function, as I’m pretty well twitterpated by this project now.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Silver activation claim:

https://youtu.be/mdqt3ac6p1E

Ran for about 6mins, -40kV, 5mA (I think), 14.3microns.

Before anyone says anything, yes my probe has been contaminated. I have ALOT of uranium minerals and didn’t realize what I was doing. Background is 1200cpm because of this contamination. Silver activation is hitting just over 2200cpm, so 1000cpm.
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Re: Matt Gibson Fusor

Post by Richard Hull »

Great work Matt you are in the elite fusioneers.

How did you contaminate the probe?
It can be easy to do by leaving the probe a very short distance from a very strong alpha emitter like radium for a protracted period. The radon production with radium decay and other of its daughters decaying in relative equilibrium will recoil and load up the mica with the various daughter isotope atoms that slam into the mica and bury themselves in it.

Leaving a probe in a grossly unhealthy atmosphere or radon gas will also do this. Keeping a probe free of this involves merely capping it when not in use. When in use, a 10 mil poly bag cover will keep the alpha and daughter recoiling atoms off the mica and still detect the beta radiation and some limiting gamma as the probe is not too sensitive to gamma.

Most of the contamination will go away in a few days or weeks and you will still have a slightly elevated background that is not significant due to the small number of the late lead and polonium 210 atoms of long half life debris still trapped.

Needless to say, never leave the probe facing upwards and open or when measuring ore samples due to microscopic ore debris falling due to gravity onto the mica during handling. Always measure face down over any source and never let the wire guard mesh touch any radioactive.

Richard Hull
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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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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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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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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.

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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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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.

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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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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.
348C6B49-EF66-4223-814B-9EFB20439025.jpeg
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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!
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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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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.
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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…
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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.
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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:
6890D7AF-8439-4421-BDAB-A9E212A044A8.jpeg
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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.

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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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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.

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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?
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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.
FDBAAC55-F519-47CA-B126-ED50C4033B11.jpeg
3 more stages to go, need the rest of my capacitors to be delivered (weeks out).
E4E0F0AD-F4D8-4588-9243-AC6D8E8950BF.jpeg
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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.
DB023823-9565-4217-A6A9-3FE4229612BB.jpeg
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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.

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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.
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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
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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
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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.
4EC3AE3A-79B7-4DA3-A8E6-780CCEACD060.jpeg
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Re: Matt Gibson Fusor

Post by Richard Hull »

You have done a great job on removing the deposition products. It is about as clear as it will get. The brown-purple tint is solarization of the glass and is there pretty much forever. It is caused by penetrating radiation, in this case x-rays and absorption of "vacuum UV" created while running the fusor over time.

This is a long known and studied process and is due to various tramp inclusion in glass manufacture. Manganese, titanium, arsenic, and antimony creeping into the glass mix is considered one of many elements and compounds that contribute to this malady. I have several old, used x-ray tubes and all have this brown solarization with a tendency in some to even be a pure purple solarization. Again, this depends on tramp clear chemical inclusions becoming colored under short wave radiation bombardment over time.

I have cleaned ports for years and this is the very best you can do.

There are a number of scholarly papers written on this phenomenon.

http://maajournal.com/Issues/2009/FullTextAbdAllah.pdf

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Re: Matt Gibson Fusor

Post by Matt_Gibson »

At least they are easy to clean up…

I’ve found another issue. I seem to have a really bad leak: I’m up over 2.5 torr in less than 24 hours. I began isolating every section by moving my gauge around. I wound up all the way down to the main pump and figured it must be the gauge itself. I swapped it out for another gauge, put everything back together, and found the same leak rate.

So now I’m wondering if something made it’s way in during all of my swapping around with the cube that could be outgassing this bad instead?

-Matt
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

I wouldn't call that a bad leak - also, since you likely opened your system to swap the gauge around, you most likely added water vapor. Its possible that is just out gassing. Time will certainly tell - out gassing will decrease in time as you keep the system closed and pumped.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

I guess I’m just used to only going up 30-40 microns after 24 hours then…I’ll try doing some heating runs once I’ve got my doodads switched over to swagelok.

How does leaking and outgassing affect wall loading? I know that letting the system reach atmospheric pressure pretty much requires you to start over again…

-Matt
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Post by Richard Hull »

I, long ago, gave up on leaks in fusor IV after it proved itself a good performer in the 1million neuts/sec mark. Its average leak rate after the end of a run, sealed- off, while still hot was 1 micron every 90 seconds!! For the picky vacuumist this is untenable! However, I proved it is not a big deal for 17 years. The diff pump could still take the system in the 10e-4 torr range and that was good enough to admit D2. If you have a good turbo or diff pump that can do this, then you are fine.

I figure it was my welds but I used up and breathed in over what seemed like a gallon of acetone vapor! Over the years, I would get a "wild hair" and hunt for the leak again and again, but zip...... Just a lot of vapor to the lungs.

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Re: Matt Gibson Fusor

Post by Matt_Gibson »

My turbo rips it down from 20 microns to 0.01 microns before it even hits 50% speed, so this “leak” isn’t affecting things from that end…I may even enable to the 66% mode to lessen wear/tear and shorten the spin down time.

I’m just concerned over losing any loading, but it doesn’t seem to be a problem?

-Matt
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Re: Matt Gibson Fusor

Post by Richard Hull »

To avoid hi-jacking this thread about Matt's fusor, I moved my reply originally posted here to a separate thread related to my issues with leaks and pump down rates in answer to Matt's posting above.........

viewtopic.php?t=14499

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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Minor update:

Swapped out my vcr4 to kf25 adapter on MFC to a swagelok fitting. I’m now able to pull the d2 line down to .01microns when I plug the polyethylene tubing, in just a minute or so. With my gas syringe, I can get down close to 1 micron. This is a huge improvement! So, swagelok from here on out…

Also, I’ve noticed that my “leak” rate is back to around 0.15 microns per minute…

As for my psu upgrade (driver portion) I’ve got a cm300dy half bridge IGBT module coming. I plan to use some gate driver ICs to drive it (via gdt) directly from my signal generator. Seems like major overkill, but it was cheap ($60) and I like overkill. Hopefully this lets me push my run times way beyond what my car amp can do and at much higher frequency (35khz vs 18khz).

-Matt
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Re: Matt Gibson Fusor

Post by Dennis P Brown »

Maybe a leak but more likely just typical out gassing. For instance, my system after pumping for two days took 90 minutes to reach 110 microns; however, after 24 hours it only rose to just 350 microns (after a few days, still only a few torr.) This is what out gassing does - it can be somewhat rapid at first after closing the system off (for a fairly clean system) but rapidly slows as the pressure rises.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Outgassing makes sense. If I close down the pumps while the chamber is hot, I’ll see pressure rise much faster than if I leave the pumps running while it cools off.

Evacuating the deuterium feed line and the MFC before operation seems to have tremendously boosted operation. I am now able to go from start to full blast in just a few seconds. I am also able to go much longer before my car amp overheats…

Btw- I enabled the turbo standby mode (66% speed) and it worked very well, so I’ll leave it like that.

-Matt
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Post by Richard Hull »

You are finding or have found your niche of operation. It takes time and relates to my recent FAQ on operation. It is an art that is homed in on by understanding all the sciences and technologies of the fusor system. Yes, the fusor might be a "stupid simple device" so far as doing fusion is concerned. However, this very simplicity and its operation on a razor thin edge between glow mode and total arc-over conditions, requires a lot of finesse and artistic skills. The science and technology of the device is a must to understand before you can do the art work to make it go and do fusion really well.

It all seems so easy and natural, once you get there. The win is not the fusion. The win is the knowledge and understanding obtained over the entire process. Sadly or blessedly, (your choice), once you have done amateur fusion really well, no one will ever be able to "pull the wool" over your eyes related to nuclear fusion, regardless of your take on its future in our lives.

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Re: Matt Gibson Fusor

Post by Dennis P Brown »

Good idea on the turbo - if reduced speed works it certainly extends the life of the pump. This also indicates your system really does not have any significant leaks.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

So I’m trying to figure out if I’ve exceeded the mega neutron mark yet. So far, there hasn’t been alot of work done with the Ludlum Priscilla probes that everyone jumped on last year. This is what I’ve been using for my neutron detection.

My best results to date:

Setup: Ludlum Priscilla probe face placed 32cm from center of fusor. Neutron oven placed 8cm from center of fusor.

13 microns, 57kV, 10mA, 4 minutes. I averaged around 7mR/hr with quite a few moves into the 8mR/hr range and a brief 9+mR/hr hit.

Silver activated to 11,000cpm on my Ludlum 44-9 probe.

Going by Ludlum’s figures, that 9mR/hr hit translates into 3150cpm. I believe a TIER number would then be 3150*12861 = 675,226n/s. Seems low to me for pushing up towards 600w into the fusor and seeing 11,000cpm silver activation.

-Matt
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Re: Matt Gibson Fusor

Post by Jim Kovalchick »

Matt,
I find it very likely that you passed the mega mark multiple times over at that voltage, current, and silver activation level.

You should able to activate some other elements too.

Nice work,

Jim K
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Re: Matt Gibson Fusor

Post by Jim Kovalchick »

How is the Ludlum giving dose rate? Is it based on thermal neutrons or is it corrected for energy?
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

What I know is that it detects fast neutrons. What it does after that, I don’t know…Above my current level of understanding :-)

Ideally, we would have a correction factor based off a bubble detector or other known detector.

I know that we probably bought the majority of these Ludlums, come on guys!

-Matt
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Jim Kovalchick
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Re: Matt Gibson Fusor

Post by Jim Kovalchick »

Dose rate in rem/hr should equate to a neutron flux that is a radiation protection standard independent of the detector assuming it is properly calibrated. There is also a difference in quality factor depending on the neutron energy.

In general one can assume that a fluence of 25 million neutrons need to come through a cm² to equate to a rem. Assuming 8 mrem/hr at 32 cm away, that equates to about 715,000 neutrons a second by my calculation.
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Re: Matt Gibson Fusor

Post by Richard Hull »

I am sure that you have exceeded the mega mark. Remember, if you are not near a beam impact on the fusor with a spherical grid, (multi-beaming), you are not getting a strong fluence as non-beam points would be more isotropic velocity space fusion which we more or less know that is not the ideal point. We live, and do, and we learn.

A large moderator on activation efforts will tend to intercept, collect and make use of more fast neutrons to thermalize and, thereby, 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
Retired now...Doing only what I want and not what I should...every day is a saturday.
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

I should be inline with a beam impact point, but should try moving the probe around a bit to see how things are affected. Looks like I have an experiment to do, after work!

-Matt
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Re: Matt Gibson Fusor

Post by Richard Hull »

A cube has two beams to split the energy of fusion into with only moderate velocity space fusion around it. The sphere or cylinder of some size with a spherical grid has many beam points to split the energy up into. These latter fusors need a huge moderator for both detection and activation.

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.
Matt_Gibson
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Re: Matt Gibson Fusor

Post by Matt_Gibson »

Got ahold of a bubble detector (23b/mR) thanks to Anze. Did a few runs today, the best one:

Using my new transformer with my 6 stage CW full wave multiplier:

66kV and 10mA at 11.66microns. Bubble detector is 35cm from the chamber center. I got 18 bubbles in 60 seconds. My Ludlum PRESCILA probe was averaging 105mR/hr at 7.6cm from chamber center.

The BTI bubble detector calculator is giving me 5.6E6 n/s! Looks like I’m well beyond the mega mark now. My multiplier should be good for 72kV but I’m hearing popping coming from it at 66kV :-(

Here’s a picture of the bubble detector. A few bubbles are on the other side and not in the photo.
CB9E5423-3CCF-47A5-B307-9A3F787FF636.jpeg

-Matt
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