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: X-ray penetration of fusor
Date: Nov 02, 1:09 pm
Poster: Richard Hull

On Nov 02, 1:09 pm, Richard Hull wrote:


I was deleting old e-mails and found an e-mail from early 99 when Scott Little was working on his fusor and we were in daily contact.

X-rays are the most serious radiation in any amateur fusor and will rise to be the predominant health risk long before the neutrons pose a genuine hazard.

Scott has many years of experience with x-ray detection instruments, having been employed in that area.

He supplied some data regarding pentetration of a standard .090 SS wall of a fusor for ever increasingly energetic X-radiation which I post below...........

Scott wrote:

I calculate the following attenuations for
your 0.090" SS walls:

Energy (keV) Fraction transmitted
20 10^-20
30 10^-7
40 10^-3
50 10^-2
60 10^-1

Of course, this doesn't really tell you what the exposure rate will be but
it gives you some indication. Also, you need to remember that, at 40kV
example, only a very few of the x-rays produced have 40 keV of
energy....most are about half that in energy.


From the above it can be seen that X-ray shielding is not a real issue until 50-60kv is applied, which I don't think anyone has approached.

I have never quite hit 30kv on my best runs, but that is due to poor vacuum control. (dirty system). The glass port is a dangerous area to approach above 22KV and using the human eye to observe here is a big no-no as it is one of the most sensitive organs in the body to radiation.

Use a cheap B&W video camera to observe the poissor. I have never looked with my eye into fusor III since the low voltage test phase in Dec 1998. X-ray leaks around this area are the big problem with fusor operation from a radiation stand point. Point this region away from you and onlookers when running fusors.

Richard Hull