In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.Subject: Weekend fusing
Date: Jan 10, 3:26 pm
Poster: Richard HullOn Jan 10, 3:26 pm, Richard Hull wrote:
All,
Well, I worked about 16 hours total this weekend on the fusor III infrastructure and fired the fusor up for fusion about 3 different times.
The system is growing and improving, mainly in the instrumentation area. The new fully digital metering of high voltage and fusor current is in place and works fine.
At first run of the newly grided system, I reached near fusion levels and then the vacuum went to hell.
I had to dismount the fusor and go back inside. It turns out that a hairline weldment crack occurred at one of the hemisphere/flange sections. It was only 1/2" long and was invisible to the human eye. I found it only due to the signature glow observed from within the chamber. I went to the spot with a 40X microscope and spotted the hairline. I wound up going over the entire hemispheric weld with the TIG setup and made the whole thing more robust. I remounted the grid and resealed with a new indium gasket.
As I took the system down in pressure I noted a reluctance to go as fast as normal near 10 microns. I checked for leaks with acetone, but the system was tight. I found out that an errant E beam was partially splattering at the edge of the viewport seal. As the seal and view[port are homemade, I used a viton gasket. The E beam was vaporizing a tiny portion of it!! I merely took a nice sized NIB magnet and carefully positioned it near the window until the beam deflected back onto the wall away from the window seal. I now have it mounted as an assembly for permanent location. The pressure then fell like a stone into the submicron range.
Fusing commenced in minutes and I now have the technique so refined that at our physics group's Sunday meeting I was able to fuse on command. (3 separate times.)
With a valved off and sealed system, I can start the operation up and be fusing in under 15 minutes. Heretofore, it was a delicate and tedious one hour "pump and grind".
The whole thing is an "artful science". Moreso with my modest homemade setup which gets better with time as old "jack-leg" materials and equipment are upgraded and or replaced.
Naturally, a "run for th' money", (critical data acquistion), requires a minimum of 2 hours preparation due to critical radiation background data collection prior to such a run.
I now have two modes I can show. The first is what I call Q & D (quick and dirty) or "qualitative" mode where the witness is treated to a rapid, but instructive startup and run with neutron detection via the victoreen/nuclear associates neutron survey meter (BF3 based). All at the meeting were most impressed. As new and late arrivals showed up, the system was cranked up again and again.
The other mode is the data collection or "Quantitative" run here I usually require an adroit assistant to manage some of the time critical details, however, I can sweat it out alone if need be. The vastly more useful, efficient, and accurate Bicron proton recoil neutron detector makes this method truly quantitative. No quantitative runs were made this weekend, due to the leak and outgas mess taking the bulk of Saturday to straighten out.
Fusor IV already has, in its parts bin, a sapphire windowed, professional, conflat viewport.
More modifications and upgrades are just weeks away. Amoung them are my capacitive electronic manaometer pressure readout. Auto current monitoring electronic feedback system, etc.
Richard Hull