Page 3 of 3

Re: Fusor progress, Finn Hammer

Posted: Wed Nov 22, 2017 6:30 am
by Richard Hull
Great work Finn! with pulses like that, you might get a regular counter to run it and accumulate for 20 minutes and take the average. My ten minute averages of 5-8 cpm using a tube with about 2-3X your volume sounds about correct. Many really good frequency counters have a count mode on their range knob.

I have several HP 10-50mhz counters purchased over the years. All have a count mode and a pushbutton for start and stop. (reset) I would hate to have to count scope pulses over that period. I have counted as low as 3 cpm and as high as 12 cpm over single minute intervals. The average always comes in between 5-8 cpm. During a significant solar CME, I have seen the local count double, and during the most massive of CME's, triple! That big one brought the aurora as far south as Richmond.............36 degrees latitude.

Richard Hull

Re: Fusor progress, Finn Hammer

Posted: Wed Nov 22, 2017 7:10 pm
by Peter Schmelcher
Finn I tested the same tube without any moderator (at sea level) some time ago and decided on proportional operation by using a 1000 volt tube bias.

One drawback you can see in the scope capture is that the neutron pulse output amplitude is smaller so shielding the electronics becomes more important.

The benefit I believe is the physics of proportional tube bias does not have a recovery time.

When you put a moderator (I used water) around the tube the initial kinetic energy gets stripped away before the neutrons enters the tube and the scope capture shows a more uniform tube pulse output (band) which you can use to amplitude calibrate your system. I do not have a scope capture with a moderator for this tube but you can see the band in the last scope capture.

The attached paper "Neutron flux variations near the Earth’s crust" pdf has a graph of neutron count rates verses altitude.

Have fun

3 minutes 1800 volt bias
CN19H 3min 1800V.JPG
3 minutes 1500 volt bias
CN19H 3min 1500V.JPG
3 minutes 1000 volt bias
CN19H 3min 1KV.JPG
1 hour 1000 volt bias
CN19H 1hr 1KV.JPG

Re: Fusor progress, Finn Hammer

Posted: Fri Feb 02, 2018 8:11 pm
by Finn Hammer
As I was walking around in the local recycling facility, also known as the scrapyard, my eyes glued themselves to a machine chassis sitting on the top of a 30 foot container, and I couldn't pass it up, because it was the perfect size. It is gross overkill, but I like that, and who can argue against a 50$ machine chassis?
Main view of future fusor layout
The presence of a chassis also prompted me to get around to performing another much needed task, the welding of a KF25 flange to the foreline of the diffusion pump.
foreline connection to the diff. pump
Another hurdle was the foreline trap. This is how it turned out:
The homemade foreline trap
This trap is filled with knitted wire mesh, which I have in abundance. I use it to make faraday suits:
Faraday suit when hit by 70kA strike
It is another story with the Faraday suit, but this one was tested at a windmill wing test facility, where they hit it with 70kA, and it stayed intact much to my own surprise, I thought it would have evaporated.
Anyway, the mesh was coated with some sort of lubricant from the manufacturing process, so I washed it out with mineral spirit (turpentine, right) and baked it with my 500deg C heat gun. This created a smoke exhaust like a small vulcano for 10-15 minutes, then it faded away, and I think the filter is fine now.
Perhaps with outgassing, perhaps due to a leak, it pressure rises by 2microns per second when I isolate it from the pump, but future leak tests will tell what is the cause. The pump is a good one, it goes down to 2 microns right at inlet, and with the filter mounted, 5 microns, so no real problem here.
Butterfly valve bypass
Calculating conductance is not yet my province, (but I am following Michael Bretti's thread closely, Thank you Michael) so in case the 4 inch butterfly valve is unable to close down with sufficient precision, I have added a bypass KF25 bellows valve so that I hopefully can get good controll of the deuterium flow into the atmosphere.
Merering side
As you see on this picture, the metering will be taken care of, by a 50 FS Micron Baratron for fusion pressure monitoring, and a 901P for the pre fusion pressure, prior to deuterium admittance. The white stick on the picture is a bar of Macor, which I will machine down to hold the extension from feedthrough to the Grid.

Sadly enough, this is going to be the only progress for quite a while, since I am moving to a new house that needs work, and this will take all spare time for half a year at the least, but who can argue against getting this view, only 60 steps from the front door:
View 60 steps from my new home.
Cheers, Finn Hammer

Re: Fusor progress, Finn Hammer

Posted: Sat Feb 03, 2018 1:33 am
by Richard Hull
Pausing fusion effort for making a livable abode in such a natural environment is a good cause. Good luck on getting things fixed up to live among nature.

Richard Hull

Re: Fusor progress, Finn Hammer

Posted: Sat Feb 03, 2018 4:03 am
by Rex Allers
Nice work, Finn. Good wishes on your move.

Rather OT for fusor, but your faraday suit image reminded me of this from the old silent movie, Metropolis.

Re: Fusor progress, Finn Hammer

Posted: Sun Feb 04, 2018 4:34 pm
by Dennis P Brown
Finn, extremely nice chamber and impressive build for a fusor so far.

You might want to consider for the chamber vacuum gauge, a wire mesh screen at its entrance to prevent the plasma from interacting with interior electronics of that detector gauge. This arrangement works extremely well for my gauge (previously, I had major issues.) Also, metal support structures always require a good, independent ground to be on the safe side (I use two independent grounds for my fusor system - two standard wall outlets ground points (each on a separate circuit) and one to a water pipe.) That way, the star system handles the electronics/transformer and I have another grounding point used by the fusor body (connected in three places to handle o-ring issues) and master power supply cabinet as well as its cable.

I too live in a very rural area and despite my extreme commute, have to say (at least for now), well worth it living in the woods near a lovely stream in an even more lovely valley. So, I tend to agree that your delay is well worth that end result - besides, it will give you time to consider issues for a fusor you might have overlooked.

As you will often sign off, cheers.