Page 1 of 1

Is bigger better?

Posted: Sat May 17, 2014 10:29 am
by Russ Gaines
I ditched the freon tank, it would have been cheaper to have a chamber custom made. I am now shopping for a chamber and was wondering, when it comes to chamber size, is bigger better?

Russ

Re: Is bigger better?

Posted: Sat May 17, 2014 11:30 am
by Richard Hull
No, it is worse! Bigger is very bad.

6" to 10" is ideal. Smaller and you might have high voltage electrical arc control issues, melting of smaller grids, etc. Larger and you will have to pump forever with a really good pumping system and waste a lot of valuable deuterium in such a huge volume.

Richard Hull

Re: Is bigger better?

Posted: Sat May 17, 2014 1:23 pm
by Russ Gaines
Thanks Mr. Hull, that will be very good to know when searching for a chamber. That being said; one more question, would I have arcing issues in a real fusor with a chamber like this one? Image Its 2.75"

Re: Is bigger better?

Posted: Sat May 17, 2014 3:49 pm
by charlie_mccartney
I am using that for my demo and I have had no melting issues with my SS grid or arcing issues at all.

Re: Is bigger better?

Posted: Sun May 18, 2014 1:30 am
by Richard Hull
Charlie is not doing fusion either, where voltages soar to 3 or 4 or more times the voltage in a demo device. Demo devices rarely exceed 50 watts while fusion devices often hit 300-500 watts. A big differrence on grid heating.

I do believe we have had a person do fusion in a 2.75 cross, but at a very low level due to all the constraints I mentioned.

If you are serious about fusion use 4" as a bare minimum and 10" as a working maximum diameter. The best fusors ever built here are 6" and 8" models. That speaks volumes.

Richard Hull

Re: Is bigger better?

Posted: Sun May 18, 2014 12:15 pm
by Alexandru_Calburean
Russ,

I will also say this: my current setup is that of a conflat cross and I find that not even 20kV at ~30 microns will get it to light off. Unless there is something wrong with my data it seems that crosses are much harder to get lit because of the PXD part of Paschen's law and the how that plays with the long arms on the chamber. Fusion has indeed been done in such a setup by two people: Chad Ramey and Will Jack, so look them up if you want to see how they arranged things in their chamber. Such chambers are a minimum needed for fusion and as Richard said will only be doing fusion at a lower level, but for the amateur with a tight budget, the 2.75in CF cross is a godsend. Good luck in your attempts.

All the best,
~Alex Calburean

Re: Is bigger better?

Posted: Sun May 18, 2014 5:49 pm
by Richard Hester
Actually the second amateur fusor (right after Richard Hull's and with a remarkably short assembly time,as all the bits were pretty much at hand) was done in a conflat cross ( a 6" cross, which would have a ~4" diameter tube) - check out Scott Little's archived data at earthtech.org. He used a small power supply (Plastic Capacitors, 20kV/10 ma), and got an estimated 10^4 neutrons/sec.

Re: Is bigger better?

Posted: Mon May 19, 2014 9:11 am
by Richard Hull
It must be remembered that in our early efforts, both Scott and I had very good neutron measuring instrumentation, something most amateur attempts today never have. The low neutron numbers of small or ill-run fusors typically demand superlative detection gear to prove fusion.

The number one failing of amateur fusion attempts is a failure to prove fusion and this, in turn, usually translates into poor to virtually non-extant neutron detection gear or very bad data collection techniques if such instrumentation is at hand.

Richard Hull

Re: Is bigger better?

Posted: Mon May 19, 2014 9:41 am
by Russ Gaines
I found a good 6" chamber on ebay I'm going to try to get, providing I can borrow some money from my dad.