Search found 422 matches

by Jim Kovalchick
Tue Jan 19, 2021 1:13 am
Forum: Images du Jour
Topic: Six Inch Cross Fusor
Replies: 16
Views: 1008

Re: Six Inch Cross Fusor

Come on guys, give me more credit than that! This was just a vacuum test. I have plenty of experience with voltages to 40 kV. The fittings you see in the photo are for a seal only. When I apply voltage, i will add features to prevent corona. Regarding the length, as I said, my tube fitting has a sto...
by Jim Kovalchick
Mon Jan 18, 2021 7:30 pm
Forum: Images du Jour
Topic: Six Inch Cross Fusor
Replies: 16
Views: 1008

Re: Six Inch Cross Fusor

I am adding a Liam David style feed through to allow boosting my voltage. My vacuum test is okay, but I holding off on properly sealing the feedthrough end until I get a grid installed that I'm happy with. The big disappointment is my tube fitting has a stop in it and is therefore inadequate. I don'...
by Jim Kovalchick
Fri Jan 15, 2021 8:09 pm
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: Extremally cheap HV feed through (if you have a lathe in hand)
Replies: 5
Views: 156

Re: Extremally cheap HV feed through (if you have a lathe in hand)

I tried my hand at making my own feedthrough from a big standoff. I brazed its skirt to a CF flange. I can easily get it in the 10‐⁵ range but it leaks easy too much for my taste. I'm not sure where it's leaking. I baked it the oven for a couple hours but that didn't help. I am looking at making a L...
by Jim Kovalchick
Tue Dec 29, 2020 4:22 pm
Forum: Fusor Construction & Operation (& FAQs)
Topic: 125kV Fusor
Replies: 13
Views: 1178

Re: 125kV Fusor

I wonder if hitting those kind of neutron numbers emitted from a small chamber like that would allow low resolution neutron radiography. I think high res requires 10⁹ n/cm²-sec, but maybe an accumulated exposure could be done on a gadox screen and a properly shielded camera with the numbers you are ...
by Jim Kovalchick
Sun Dec 20, 2020 12:49 pm
Forum: Fusor Construction & Operation (& FAQs)
Topic: Progress Update
Replies: 22
Views: 1376

Re: Progress Update

Joe,
Thanks for sharing. Yours is certainly a premium, benchmarkable setup. Do you use any shielding?

Jim K
by Jim Kovalchick
Thu Dec 17, 2020 11:58 pm
Forum: Images du Jour
Topic: Six Inch Cross Fusor
Replies: 16
Views: 1008

Re: Six Inch Cross Fusor

Update:
This evening's run: -38 kV 6.8 mA. A count rate of 5700 cpm was observed for the first 5 minutes after which the count rate steadily dropped to below 4000 cpm when I shut it down.
by Jim Kovalchick
Thu Dec 17, 2020 9:47 pm
Forum: Images du Jour
Topic: Six Inch Cross Fusor
Replies: 16
Views: 1008

Re: Six Inch Cross Fusor

First real fusion run on this fusor iteration today. Before I could get to fusion relevant voltage I had to remove the alumina from the stem. I'm not sure why I bother putting it on in the first place because I don't have the best of luck with it. The alumina tubes seem to cause a lot of sparks. My ...
by Jim Kovalchick
Wed Dec 16, 2020 2:37 pm
Forum: Images du Jour
Topic: Six Inch Cross Fusor
Replies: 16
Views: 1008

Re: Six Inch Cross Fusor

The tungsten carbide ring is too small and caused control problems. I may buy a larger one, but in the mean time I substituted a singled braided tungsten wire ring. The larger diameter improved my ability to control at lower currents that make conditioning easier. Symmetry is a little better this ti...
by Jim Kovalchick
Wed Dec 16, 2020 12:09 am
Forum: Images du Jour
Topic: Six Inch Cross Fusor
Replies: 16
Views: 1008

Re: Six Inch Cross Fusor

Mark,
I had previously tried Ti plates at the beam ends. It outgassed terribly.
by Jim Kovalchick
Tue Dec 15, 2020 5:18 pm
Forum: Images du Jour
Topic: Six Inch Cross Fusor
Replies: 16
Views: 1008

Re: Six Inch Cross Fusor

My small fusor was arc limited at 38 kV. The arcs were ferocious and destroyed instruments. . The tungsten carbide ring is a wedding band. They cost about 11 dollars on ebay. I will probably go with a larger size than the one in the picture because the control characteristics are rough. It's too har...