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: Fusor size
Date: Jun 23, 11:53 am

On Jun 23, 11:53 am, wrote:

>>It is a simple question, is there some real scientific reason why an amateur Fusor needs to be larger?
>>Engineering wise a smaller fusor seems possible just not as impresive to look at.
>>Nathan K.
>Again, this issue was dealt with in a post of about a year ago.
>I noted that the ideal size for an amateur fusor was in the 4-8 inch diameter range, with 6 inches being superb.
>It is correct that if you want to do the simplest and easiest fusion, which is glow mode fusion, the 4" - 6" sizes are about the only size you can make.

Another consideration is that very small fusors will have problems with HV breakdown along the insulators, and through the gas. As the system gets smaller, the field at the inner electrode gets higher (the voltage has to be high enough to impart enough energy for fusion (i.e. 20 kV)). Flashovers will be more likely.

The other issue, although I am not sure it is all that significant, is that the mechanical tolerances required are roughly a constant percentage, so if you make a 1 cm diameter fusor, you'll need to machine stuff to a much higher precision.

>As Nathan points out now and I pointed out a year or two back, the smaller volume will pump quickly and be less wasteful of the relatively expensive deuterium gas.

Of course, as you pointed out, Richard, a lecture bottle of D2 will last a VERY long time, no matter how big your chamber is. 2 scf in a lecture bottle will fill a 1 ft diameter chamber to 1 torr about 3000 times. At 1E-6, it's 3 million times... I don't think D2 consumption expense will be the budgetary constraint.
>The idea of an amateur fusor a meter in diameter is ludicrous as the support materials would cost tens of thosands.

Even if you got the materials for free, the electricity to run the pumps and the chillers for the cold trap would be a substantial expense.

A good practical size is one that allows you to use normal sized tools and not have to work with a microscope and a micromanipulator. Hmm, though, I have wire/ribbon bonders and other such stuff at work, maybe I could spot weld up a tiny, tiny sphere? Is there a minimum size that will work?