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: X-ray Hazard
Date: Mar 08, 11:53 am
Poster: Richard Hull

On Mar 08, 11:53 am, Richard Hull wrote:

>Below 11 KV, it just ain't an issue, pretty much as Richard said. However, between 11 KV and about 35 or so X-rays are actually MORE of a hazard than at higher voltages, because at lower energy they are absorbed entirely in the body and at higher energy a significant fraction just pass on through.

These are the so called "soft x-rays" I have mentioned them a long time ago in an older post on x-ray hazards. These are burner rays!!! They are not hazardous to deep tissue. Basically they are about as bad as a real bad sunburn and will cause cancer at about the same level of exposure per watt-cm. I consider soft rays ending at about 20-25kv. The hazards to fusor operators in the 15-20kv region approach zero even if the port shines right at you from two feet. Such a test of this theory would be silly when it can be easily aimed away. lead foil stops this stuff dead and I used bar solder to stop the stuff. At 30kv there is still no measurable output from any part of the fusor here, unless I uncover the port in some fashion or the x-ray shield moves to expose a crack. Point blank, port uncovered, with an Eberline cutie-pie at 30kv and 10ma. I get about 6R of rays. This is dangerous from any point of view.

I remain stunned and yet gratified that the CCD of the video camera permenantly looking into the chamber has no bad pixels yet! A lot of sparkly flashes are seen as the little guys discharge due to x-ray hits, but they come back for more. The lens undoubtedly filters out 100% of the low end and soft rays.


>Now, legal stuff: we apparently need a certified health physicist to review our specs and give us a letter on what is safe and what isn't. Several mm of lead is recommended, or its equivalent (which the healthy physicist must look up and certify).
>Yes, the nanny state is alive and well in America. On the other hand, when it's my son, I have a tendency to be real, REAL paranoid. It's just my nature, and he doesn't like it one bit (he's 16, but then he'll get over that eventually).
>When I get more info than a 10 minute call over my cell phone when I couldn't take notes I'll post more. Don't rely on the above figures since my recollection of the conversation could be faulty.
>Bottom line: X-rays at 15 KV could be more than a sunburn. Also, as my radiologist friend reminds me, a sunburn IS a radiation burn.


Absolutely Radiation is radiation and the beach bunny's will look like old burned out alligator bags in their later years, too. They are the same fools who demur at the horrible difference in a 1/4 second exposure to x-rays over a 5 second one while baking their entire carcasses year round under sun or in tanning salons. Go figure. The stigma cachet is on X-rays. Nearby stellar fusion reactors are OK.

The eye is the organ to watchout for in fusor work. It is the weakest and most radiation sensitive organ we have. Simple protection is all we need unless probing the 50kv and above regions.

Richard Hull