Demo Fusor close to first light

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Larry Upjohn
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Re: Demo Fusor close to first light

Post by Larry Upjohn » Fri Sep 12, 2008 9:29 pm

Thanks to everyone for your thoughtful input. My powersupply is only partially wired so the ground through the ammeter is not evident. The caps are wired in parallel and as noted were in a circuit with a sparkgap to provide highfrequency high voltage AC coupled to an arc welder output for "cheep" no touch TIG arc starting. It did not arc over in that application so hopefully will not arc in DC mode. BTW I have dremeled off most of the unecessary copper on the backside of the board to prevent arching. The stalk will be insulated with ceramic tubing when it arrives. The teflon plumbers tape is an admitted cludge. I will probably retain it only on the base joint, the TC guage coupling. I will probably seal the remainder using silphos or silver bearing solder. If nothing else I hope my efforts lead to reproducing the fusor experiment. I am after all standing on some tall shoulders here. Larry Upjohn.
Larry Upjohn

Larry Upjohn
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Re: Demo Fusor close to first light

Post by Larry Upjohn » Mon Nov 10, 2008 6:10 am

Tonight after a flight home from Seattle I have applied voltage for the first time. Vacuum is noted on the photos below. The lowest is just chamber pump down with no power to the grid. The second guage photo represents pressure increase with grid power. First two grid photos are the early scintillation noted when power applied. This started to appear when the voltage was around -1100 volts. My ammeter circuit is not working as connected so will need to revise it to a properly shunted analog ammeter movement. Final photos are of the grid glow. Got several beams which heated inner grid on one side to redness with formation of distinct intense blue plasma inside the grid. I switched off the variac to avoid melting grid or glass globe. Finally I ran the power at a lower level, scintillation gradually disappeared and glow seemed to focus inside inner grid. No finally focused poissor appeared but this is only my demo plasma to begin with and I shut everything down for the night. The glass globe is now nicely coated with a deposition looking similar to carbon that we used to coat transmission electron microscope samples with. Glass was slightly warm on the side of the grid that got incandescant. No radiation instrumentation used as total voltage never exceeded -4.5kv. I appologize for the quality of the photos as taking pictures and keeping clear of the HV in the relative dim lighting was enough to handle right now. More later, Larry Upjohn.
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Larry Upjohn

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Steven Sesselmann
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Re: Demo Fusor close to first light

Post by Steven Sesselmann » Mon Nov 10, 2008 7:16 am

Larry,

Congratulations on first light!

I am no expert on regular Farnsworth fusors, but to me it looks as if your vacuum gauge is showing a better vacuum that you are achieving.

Some of the other guys might confirm this, by the appearance of the plasma.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

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Richard Hull
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Re: Demo Fusor close to first light

Post by Richard Hull » Mon Nov 10, 2008 3:21 pm

Larry, Your name is added to the plasma club listing.

Nice first light. This is always a major moment

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.

Larry Upjohn
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Re: Demo Fusor close to first light

Post by Larry Upjohn » Mon Nov 10, 2008 9:49 pm

Steve;
I have already budgeted a Baratron style capacitance manometer for my "real" harder vacuum guaging. This TC sending unit has been rehabed after oil contamination so it a qualitative guage right now till the Baratron is on board. More later, Larry Upjohn.
Larry Upjohn

Larry Upjohn
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Re: Demo Fusor close to first light

Post by Larry Upjohn » Mon Nov 10, 2008 9:52 pm

Thanks Richard. There is much more to do, starting with a cleanup of my limited work space, improvement of my project realization and etc. I am still working two jobs so time is much at a premium as well. I am threatening to retire to just one job here soon. More later, Larry Upjohn.
Larry Upjohn

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Re: Demo Fusor close to first light

Post by Larry Upjohn » Wed Jul 22, 2009 4:02 pm

Have refined the Demo Fusor to eliminate the Glass Globe. I replaced the silver soldered inner grid as well. I managed to deposit molecular silver over the interior of the globe internal components including the insulator of the Sparkplug. It cleaned right up with silver polish. Inner grid is all stainless now with an thick walled aluminum pot serving as the bell jar now. Larry Upjohn.

Pictures include the new chamber, new inner grid and yellow teflon tape I have found that seals NPT fittings quite well.
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Larry Upjohn

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Re: Demo Fusor close to first light

Post by bk8509a » Mon Dec 07, 2009 8:26 pm

How did you make that beautiful inner grid?

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Re: Demo Fusor close to first light

Post by DaveC » Mon Dec 07, 2009 10:24 pm

Larry -

Nice work!. I was also going to compliment you on the beautifully done inner grid. A definite work of art!

My only caution is about your ball valve on the vacuum line (unless I've misunderstood what I see). The in- line seal around the ball is probably fine for these purposes, but I wondered about the stem seal, it could leak enough to add to your residual gasses.

Dave Cooper

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Doug Coulter
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Re: Demo Fusor close to first light

Post by Doug Coulter » Tue Dec 08, 2009 12:41 am

Very nice, this is a great start!

I admire your cool grid as well, but here haven't had much luck with spirals, for whatever reasons, I've not pursued them. I'm the cylinder grid guy here.

What struck me right off is the use of the sparkplug backwards -- that's smart. It can be real hard to keep a discharge happening on the other end in low pressures indeed, and hard to fix once it's happened, the long insulator in the vacuum is the way to go for sure.

It is getting tough to find non resistor plugs, and the ones that have like 10k R in them burn out very easy, especially the way yours is -- no good way for heat to get out. BillF found us some really really old ford plugs, like for model T or something, that not only have no R but are simply huge on both ends (Standard NPT on the engine side as a bonus) and for those I was able to find some ceramic tubing to extend the insulator on the "inside" side after welding (not brazing) a longer wire to it, and it's still in service on his machine as a feedthrough for the ion source.

I used an oldie but goodie glue formula for that -- sodium silicate with talc made into a slurry. It gets hard like epoxy, but it takes a looooong time, as in a few days to do so. A few more days at sub boiling heat and the water if finally gone and it will then stand yellow heat, and sticks really well to these things. If you heat it too soon -- it goes bang, the hardening process is not the same as getting the water out.
Why guess when you can know? Measure!

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