Fusion Message Board

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: Re: More bad news for fusors
Date: Jul 18, 10:37 am
Poster: Richard Hull

On Jul 18, 10:37 am, Richard Hull wrote:

>Richard maybe A lot of the heat you have been talking about, on the fusor shell, is coming from
>the bremstrathlung radiation being absorbed.


I suppose you might want to call it that, but I look at the main case heat mechanism as simple electron-case-shell collisions. The copius source of electrons is the nearly white hot inner grid (tantalum). These accelerate towards the positive outer shell and impact it. X-rays, bremstrahlung, a few nuclear impacts, etc are the result.

Remember we often think of bemstrahlung as a penetrating radiation but in this case it is only the lowest and cruddiest form of IR radiation.

A good reference on X-ray production (tube manufacture) notes that most X-ray tubes of the best type are only about .01% efficient in the production of X-radiation at or near the full acceleration potential. It is readily stated that Bremstrahlung in a heat production mechanism in X-ray tubes.

I say this due to many folks having an idea of the word "bremstrahlung" as being a super potent radiation or it evokes images of horrid nuclear slow downs with lethal consequences. In a 30kv fusor it is crap lucky to make low grade IR range. RH


>On another subject. Do you think the QF type vacuum flanges will work on my SS fusor shell?
>I'm worried about the O-Rings outgassing and maybe getting to hot. The QF's are simpler to make and the O-Rings are cheaper to replace. I
>need flanges to join the two shell halves together and the prices for commercial flanges seem to be in excess of $200 for the 6 in. Id units. Any help based on your experience or judgement will be appreciated.

QF or KF flanges are fine for all but UHV applications. I would not hesitate to use these flanges to 10-6 torr. I would also never use a quick flange of more than 2" diameter and prefer QF-16 and QF-25. I would never use some kludged up 6" QF gasketed system to hold fusor halves together!

For fusor halve joining use only conflat or ASA fittings. The $200.00 for both 8" rings is a deal.

Basically, over broad surfaces use a metal-metal contact gasket seal ONLY! (conflat-copper or flats -indium). Use viton gaskets only on small vacuum fittings or inlets. If going deeper than 10-6 torr, use all metal to metal seals throughout high vacuum side of the system.

A lot of this technique stuff in on the new tape.
You really want to go no deeper than about 10-4 torr on the simple fusor system. This can be easily accomplished with a superb, clean, two stage vacuum pump and a micromaze.

Richard Hull
>Don Harris