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: Pesky ole X-rays
Date: Nov 01, 09:23 am
Poster: Richad Hull

On Nov 01, 09:23 am, Richad Hull wrote:

The Fusor III is now working regularly at 25 KV and the X radiation from the port sides is really getting up there. It makes my Eberline "cutie-pie" ionization meter really cook at about 50mr/hr. These are rays of extremely low penetrating power, but capable of causing rather severe skin surface burns. This thin disk of rays are totally stopped by a thin 1/4lb bar of solder which was simply bent around the port edges.

It was determined that the exposed edges of the port glass were the source of the rays as they scatter over a wide angle as the electrons pound the silicon atoms in the glass.

My view port, was never meant to be for the human eye, though it can be used for inspection that way at voltages under 10kv. Even at 1.5", it is way too big as I have a micro single board video camera doing the looking for me as many have seen in the photos on a number of sites. Since Stephen Coley's new site is down or not up yet in its new form, the best source of images, (although older), of my stuff remains Jochen Kronjaeger's web site at the Univ. of Marburg. Stephen has his web site's front door up though and a really good image of my star mode adorns the intro page.

For those with simple demo fusors, X-rays are no problem, but let 12 KV be the limit to carefree, non-radiative systems. You simply must have some form of radiation instrumentation if you fiddle around above 15kv. Real metal fusors will afford great protection up to about 30-50KV with only window ports being a source of dangerous X-ray beams. These can be planned for and the xrays easily dealt with, but you have to know about where the radiation is, how much of it there is, and whether your efforts to stop it have met with success. Only a Geiger counter or ionization chamber type survey meter will help.

A word of warning to those buying off E-bay. Almost nothing works which is purchased off E-bay. It is junk with a capital "J".

90% of the ads are jokes with a standard cover of "unable to test"....Sold as is.....Didn't have batteries...Worked when last tested, etc., telling you "IT'S BROKE!!".

Also, 90% of the items are Civil Defense ionization chambers which have a high end of 500R! Even if working, these babies wouldn't read until after a total, all out, nuclear exchange and then you would need to be in the crater!

Most folks really don't know much about nuclear instrumentation and suffer mightily at the hands of E-bay hucksters. A lot of the older geiger counters/survey meters/scintillation counters require (2) 67.5 or 45 volt bateries, some also need a 30 volt bias battery. Some even require the large long discontinued RM-4 mercury cells. The 67.5 volt battery costs about $25.00 each. So, a $35.00 win with a "Lucky Strike" gieger counter off E-bay means you are still about $55.00 away from getting it to work. (assuming perfect condition after 50 years!)

Be careful and only shoot for true geiger counters (with hand piece) or an eberline type ionization survey meter with a top range of 5R and a low range of around 5MR. Also make sure the thing works and uses only common "D" cells and or the normal 9 volt transistor batteries. it would be nice to have the ad say that the thing works or is warranted to work. (fat chance).

Good luck on getting intrumented for X-rays.

Richard Hull