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New Fusor Project

Posted: Fri May 24, 2019 12:02 am
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

Re: New Fusor Project

Posted: Fri May 24, 2019 3:43 am
by Richard Hull
I, too, have thought about giving this a whirl. Still just musing over it.

Richard Hull

Re: New Fusor Project

Posted: Sat May 25, 2019 11:15 am
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.

Re: New Fusor Project

Posted: Sun May 26, 2019 12:08 am
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.

Re: New Fusor Project

Posted: Sun Jun 02, 2019 1:27 am
by Mark Rowley
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

Re: New Fusor Project

Posted: Sun Jun 02, 2019 9:13 am
by Richard Hull
Looking very good! Slowing to a pace that warrants the best form of assembly and testing in a good and proper order.

Richard Hull

Re: New Fusor Project

Posted: Fri Jun 14, 2019 5:48 am
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.

Mark Rowley

Re: New Fusor Project

Posted: Wed Jun 19, 2019 7:41 pm
by Mark Rowley
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

Re: New Fusor Project

Posted: Wed Jun 19, 2019 8:16 pm
by Richard Hull
That is one beautifully clean stack! Keep up the good work and reports.

Richard Hull

Re: New Fusor Project

Posted: Thu Jun 27, 2019 5:56 am
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