FAQ: X-Rays and the fusor

If you have a question about this topic, the answer is probably in here!
Post Reply
User avatar
Richard Hull
Posts: 11255
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

FAQ: X-Rays and the fusor

Post by Richard Hull » Tue Oct 14, 2003 3:18 pm

The fusor will make X-rays long before it does fusion! (produces neutrons)

Internal X-rays can begin at 10kv, but no real X-rays will exit of a significant or, often, even measurable amount until one reaches 15kv applied.

Bell jar demo fusors operated above 15kv are particularly nasty. DO NOT OPERATE A BELL JAR AT THESE POTENTIALS. X-rays are not attenuated well by common borosilicate glass.

The metal bodied fusors will leak X-rays at the view port at around 15kv applied. Shield this area with lead or point it away from the operator or bystanders.

The more the input voltage is raised, the more serious are the X-rays from a health physics standpoint and the more dangerous a view port becomes. At 25 kv applied serious health problems arise at the view port. SHIELD THIS ENTIRE REGION OF YOUR FUSOR.

If one increases the voltage to do fusion beyond 35 kv then the average .060" thick stainless steel fusor shell starts to become more and more transparent to the rays. Here and beyond, the entire fusor become a serious X-ray radiation hazard and MUST BE SHIELDED.

Shielding should be made of lead for X-rays. 1/8" to 1/4" sheeting is usually more than adequate. If the device is in a home or apartment then it should be shielded over its entire form. If in a garage or out-building then it only needs shielding to create a safe shadow cone for the operator and observers to stand in as the inverse aquare law will protect the neighbors adequately based on the very limited operation times of the average fusor. Still, it is best to even shield them as it would only require about a 12" square piece of lead to shadow cone an entire building next door.

Detectng the Rays and Quantifying exposure:

A geiger counter will INDICATE the presence of X-radiation.

To get a quantitative figure of exposure or accumulated dose you will need a "cutiepie" type ionization chamber meter or an integrating dosimeter of the pen or pocket pager type.

Again, none of this is needed at all when operating any fusor type device under 12kv.

X-rays are a serious issue with the fusor only if you are attempting fusion. With demo fusors and normal plasma based systems which operate well under 10kv x-ray protection and detection are a non-issue and need not be addressed at all. In such systems, coming into accidnetal contact with the high voltage poses the main danger.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Post Reply