New Fusor Project

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Mark Rowley
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New Fusor Project

Post by Mark Rowley »

After reading about the successes of the 2.75” 4-Way cross fusors, I decided to pattern my next build after Robert Dwyer’s success. As of now, I’m in parts gathering mode and have currently assembled what’s shown in the picture. For vacuum, I currently have a Yellowjacket roughing pump and a Varian HS-2 diffusion pump. Both have been successfully tested on the bell jar Fusor I recently posted about. Deuterium will be supplied by a PEM Cell / Drierite arrangement which I purchased a few months ago. For neutron detection I have a Ludlum 2221 / Remball arrangement, a host of BF3 tubes, and some other odds and ends. HV, like many others is my weaker area. I do have several 70’s era dental type X-ray transformers, a 30kV / ~20ma Universal Voltronics transformer, and a 40kV /7.5ma GHVR supply (needs work). Ultimately, after everything is dialed in, I’d like to try getting a precipitator psu to generate some neutrons.

Aside from needing more fittings and misc hardware, I have a ways to go before getting air plasma in this thing.

Looking forward to the fun and challenges!

Mark Rowley
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Richard Hull
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Re: New Fusor Project

Post by Richard Hull »

I, too, have thought about giving this a whirl. Still just musing over it.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: New Fusor Project

Post by Dennis P Brown »

Sounds good overall - I too have a 2.75 system (complete relative to parts) that I will assemble late fall when I have time - I'm in no rush since I've done fusion. But I was forced to get a new power supply; my old one had to be returned but I really liked it. While only capable of 32 kV, it could handle surges of over 100 ma with no issues. Now the new supply (70 kV) will be lucky to handle its full 15 ma. It will have to be under oil as well unlike my old supply.

Definitely use a proper power supply first (i.e. when everything is all dialed in) - then after generating and detecting neutrons do try the precipitation style supply. Just realize that it is very likely that the Chinese supply will only allow/enable very low level neutron production so a good, proven detector system will be needed.

Creating your own deuterium gas (remember, needs to be super dry) will only supply a very limited amount of gas - so good control of the vacuum system flow rate via a main throttle valve will be essential for the DP to camber so you don't consume your gas too rapidly.

Best of luck and I hope you get your system up and running very soon.
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Mark Rowley
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Re: New Fusor Project

Post by Mark Rowley »

Thanks Dennis.
I like Rex Allers and Rich Feldman’s idea about using a new, never before inflated, Mylar balloon as a gas reservoir. Once full I can isolate it from the PEM cell cell and connect it directly to either project. And as stated, Drireite will be used.

Being that the PEM cell arrangement is unique, I’ll generate a dedicated post once I start assembling it.

Mark Rowley.
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Re: New Fusor Project

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Just a brief update on the project status and my current assemblage of parts. I still need a couple more fittings before vacuum testing begins. So much to do! The big to-do list includes:

Vacuum testing the HV Feedthru and repairing any leaks.
Assembling the HV power supply (inc ballast resistor)
Wiring up voltage, amperage, and vacuum meters
Building the tungsten grid assembly
Assembling the Deuterium PEM Cell and gas collection / handling system.

And of course there is the usual time consuming minutia in the midst of all this.

Mark Rowley
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Re: New Fusor Project

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Looking very good! Slowing to a pace that warrants the best form of assembly and testing in a good and proper order.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: New Fusor Project

Post by Mark Rowley »

Performed a little more work on the Fusor today. Assembled the chamber, routed the bellows hose to the diff pump, and vacuum tested the system for the first time.

The first problem seen were leaks along the HV Feedthru weld. I halfway expected this so I know what I have do.

After replacing the feedthru with a cf blank )as shown), the chamber did much better but far from where it should be. I’m having issues with the Ritchie 6cfm Yellowjacket. It just won’t pull below 45-50 mTorr on in its own. When I first bought it in 2003 it could easily pull 10 mTorr after about 45 mins of pump time. Overall it has about 25hrs of run time so I’m not sure what the deal is. I’ve vented the ballast for awhile as well as changing the oil. I’ll probably switch over to the 1402 sometime tomorrow until I get this sorted out.

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Re: New Fusor Project

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A few updates. Rectified a slight leak issue with the HV feedthru, cleaned the HS-2 tree, and had an annoying issue with overall vacuum bottoming out at ~25mTorr. Come to find out it wasn't a leak, it was a faulty DV-6M TC. Now I can move on to gas handling, power supply, and other matters.

Mark Rowley
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Re: New Fusor Project

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That is one beautifully clean stack! Keep up the good work and reports.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: New Fusor Project

Post by Mark Rowley »

Today I conducted a preliminary test of the entire system up to 17kV. By doing so I learned quite a bit, especially regarding a few design flaws. I’ll outline them individually:

HV Power
So far I’m very pleased with the transformer. It’s endured several hours of tests at various power levels, including amperage inducing pressure burps. As long as I keep the power levels 10ma and below, I think I’ll be fine. During the end of today’s tests I noticed some very slight arcing towards the edge of the ballast resistor. Totally my fault as I used a 50 watt wire wound as opposed to a 100 watt. Upgrading will be the next step.

HV Meter
I’m using the free meters from Harbor Freight. The milliamp meter works perfect but for some reason the volt meter begins to go wild and flicker over 15kV. I’m using two 2.5 watt 100meg ohm 20kv resistors in series and they are contained in oil. This shouldn't be a difficult problem to solve. Thinking it’s possibly related to the grumpy ballast resistor.

Neutron Detection
Although today’s test was done with air, I wanted to see how electrical noise and xrays interacted with the CHM14 / Ludlum 2221 arrangement. As expected, no issues with the xrays, but electrical noise caused some problems. Placing the 2221 directly on the Fusor cart seemed to be the cause of the noise. If I put the 2221 on the adjacent wood table and run the CHM14 to within 7–10” of the Fusor, noise problems ceased.

Inner Grid
At 14kV and up, I noticed some intermittent flash over near the alumina grid stem and the nearest part of the chamber wall. Probably needs another layer of alumina insulation. Also, compared to other 2.75” systems, my grid is a bit bigger at around 0.75” dia. When I address the arcing problem I may replace it with a 0.50” dia version.

Chamber Pressure
Ive read tons of posts here about how pressure, voltage, and milliamp adjustment is an art form. And as I’ve learned, it sure is! Since getting the the transformer working a few days ago (and before with an NST) I’ve been practicing quite a bit. It also served to condition the chamber via glow cleaning as well.

Xrays
Always keeping a safe distance to the side of the viewport. I’ll eventually hook up a video camera but for now it’ll be a mirror and a selfie stick. I did have some fun with a refurbished / vintage PRI 111B scintillator with audio squealer positioned across the room and in direct line with the viewport. It provided a nice audio alert when xray emissions began. In addition to that I used an Eberline pancake and a digital GammaGuard CT007-N scintillator.

Shown is a pic of the Fusor in its current configuration and a 15kV plasma.

I’ll post another update when I get all this sorted out.

Mark Rowley
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Re: New Fusor Project

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Note the harbor freight meters, especially in voltage mode are high impedance and they are not noise shielded internally. This may explain the volt meter going nuts.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: New Fusor Project

Post by Cai Arcos »

Following from my own personal experience regarding those cheapos, I would second what Richard said. Noise is quite an important issue, specially in your setup where everything is packed close together. Sparking between the contacts of the rotary switch might also be a problem (as it happened to me). What's worse, the noise will show incorrect and inconsistent issues (see my recent threat in the matter).

I have since changed to a much simpler voltmeter like this one (https://www.amazon.es/MakerHawk-Voltmet ... ols&sr=1-1) and adapted it's impedance. Still sensitive to noise, but when it fails it stops working completely, thus letting me know something is wrong. Ultimately, I will move to analog metering I picked up in the recent HamFest.

I do not see the entire wire set up, so this might not help, but I often found that noise happened much more frequently when the wire coming from the resistor to the multimeter itself was close to that of the HV PS. Might be spacing them more (using separate tubing or similar) would help. I definitely do not see how the ballast resistor is at fault here.

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Re: New Fusor Project

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Thanks for the response Cal. After yesterday I’ve been considering going full analog. I’ve have access to quite a few 50uA meter so I may be testing one in the near future. Being an aficionado of vintage electronic gear, I’d like the appearance as well.

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Re: New Fusor Project

Post by Richard Hull »

Analog is fine if you have the old meters. The Harbor freight meters are great for pure DC and 60hz AC, and in relatively noise free environments. Digital meters will always read easier provided your voltage is not bouncing around. If it is moving about a specific voltage, an analog meter will be easier to read as its response is poor and will give you an average around the voltage present.

For the fusor, an analog voltmeter really needs to be a 20ua or 50ua meter movement to keep the power requirement of the dropping resistors low.
An analog current meter can be 500ua or less, although 1ma is OK.

For older meters made before or during WWII, make sure they are accurate to full scale as magnets weren't all that stable then. Used a harbor freight meter in series with you analog meter under test along with a variable power supply and a suitable dropping resistor. You might be surprised at how far off older d'arsonval meters might be.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: New Fusor Project

Post by Mark Rowley »

Deuterium Star
27.5kv / 2.85ma / 35mTorr

My corona tube seems to do well with a PoBe source but the electrical noise from the Fusor is wreaking havoc. Since I want to move forward with the Columbus-1 pinch tube project, I'll just bite the bullet and get the Bubble Detector. I'll need it anyway.

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Re: New Fusor Project

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Noise seems to be and has been an issue with the Corona tubes. Some folks seemed to have licked the issue. Nothing reports like the Bubble dosimeters or activation techniques.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: New Fusor Project

Post by Dennis P Brown »

I got around this problem by encasing my detector tube in a copper pipe with soldered end caps (one cap had a high voltage coaxial connector); of course, co-axial cable for all devices including the power feed. My power supply was an isolated battery/inverter/high voltage supply so noise from the fusor via the house wiring wouldn't create any issues via ground loops. Worked extremely well.
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Re: New Fusor Project

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I was just about to do something similar. Last night and this morning I spend several hours going through the forums and found some good info from Lukas and Carl. Instead of going for the standard bias of 700v, I set it just for the cusp of corona mode at 670v (as suggested by Lukas). I then cleaned up my connections and swapped in a much heavier shielded cable. That was the fix. Practically removed all noise. And you’re not kidding, once dialed in, these corona tubes work good.

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Re: New Fusor Project

Post by Richard Hull »

"dialing in" is the issue with Corona tubes and boron lined tubes. They do not operate correctly, unless fine tuned by a careful hand. Like any such electronic adventure in neutron counting, once "dialed in" you can replicate it at any future time. You have learned what is good and what is bad in the process due to a good bit of hands-on effort. You know when it is right by the application of artifice as much as science.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: New Fusor Project

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After multiple fusion runs, I can see that the following modifications will have to be made before I can proceed much further.

-Reduce grid size from 0.50” to 0.30”-
Uneven heating on the grid seems to suggest half inch is still too big. The outer ring seems to get red hot long before the inner ring which may be due to its slightly closer proximity to the shell. I’ve been told 0.30” dia is probably the best size for a 2.75” system.

-Pot HV supply in oil-
It’s totally clear 30kV is the corona ceiling for the precipitator supply which totally limits any performance improvements. At just over 30kV corona losses are huge.

-Increase deuterium purity-
My Horizon PEM cell tends to slow to a snails pace after 2 minutes. One 100ml charge currently takes over two hours to fill. The plastic syringe I’m using as a reservoir only lasts about 3-4hrs before air totally contaminates the deuterium. I’m considering a glass syringe or revisiting the Mylar balloon idea. Direct feed doesn’t seem feasible with the higher deuterium pressures and my oversized and thirsty HS2 diff pump. Regarding it’s slow production rate, the manufacturer recommends cycling it back and forth between generating electricity and gas about 6 times. Seems to help, but it’s still a far cry from when it was new.

-Install additional xray shielding-
Just a necessity. I already have shielding via the heavy bricks, but I’d like more. 1/8” lead sheeting is on the way.

-Install video camera-
Ive learned that operating the Fusor solely on IFR is pretty easy. There’s almost no requirement to see the plasma but not having the visual removes a lot of the fun! Its also probably good to monitor the integrity of the grid as you push the system.

-Install analog milliamp meter-
The cheap DVM I’m using for amperage monitoring does way better than the free HF units but it still gets a bit fluttery over 25kv. Ultimately I plan on using a good digital system but for now I’m going to install an analog milliamp meter.

Mark Rowley
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Re: New Fusor Project

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For me, the only reason for a view port is to monitor the grid heating as you push the system. I have long ago gotten rid of the "oh, look at the pretty star" fascination. Video monitoring is both safe and allows you to view the grid on a 50 inch flat screen is that is your "thing".

Analog metering is fine, but by 2004 I went all digital, when I could buy 4 digit bright red LED 200 millivolt, fixed panel meters for about $20.00 each. I tuned them into my system with dropping and shunting resistors and they are still there today. Such really good 1" tall LED digital panel meters are rare today and when found are more expensive.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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