Stopping X-rays
Posted: Fri Jun 22, 2001 2:46 pm
I recently spoke to this question on the old intranets site, but it was not posted in the radiation forum. So here goes another pass in the proper forum.
X-rays are the first major radiation to issue from the working fusor and continues to get worse as the applied voltage rises.
Most amateur fusor demo models never produce a single x-ray and are therefore pretty benign in this area.
A deuterium filled fusor operated above 10kv will not only start to produce neutrons, but x-rays as well.
It is rather difficult to get a serious neutron flux from any amateur fusor operated under 30kv. Thus, the neutron hazard from short period runs in fusors up to 30kv is not a serious or immediate hazard.
X-rays, are another matter. They begin to spill out of viewports at about 12kv and the intensity grows to a dangerous level by 18kv. A geiger counter placed near a viewport at 20kv will usually saturate the entire counter and stop it from working, temporarily!!!
Ionization counters are best to sniff out x-rays and obtain a quantitative exposure. However we don't care about quantitative. We only care about detection. So most any low cost geiger counter will serve to alert us as to where x-rays are leaking out.
X-rays in the 15-30kv range are, for the most part, "soft" and are, therefore, considered "burning rays". They will be stopped totally in the first few millimeters of flesh and do maximum damage. (burn) by the same token they are easily stopped dead or shielded totally out of the picture. If you are not using your view port, cover it with a 1/16 inch thick sheet lead cover or a 1/4" thick aluminum disk. continuously sniff around this area with a geiger counter when the fusor is running to check for x-ray leaks at the edges.
Most of you will want to stuff a camera into the viewport and remote view the opertion on a video monitor. Make sure the area around the camera's lens and viewport is shielded to avoid scattered radiation.
Most metal fusors will have a lethal x-ray problem emerge when the entire shell becomes transparent above 70kv, but that is another issue and no one is likely to be there any time soon.
Remember, the eye is one of the most sensitive organs in the body to radiation. Never stare into a view port with high voltage in excess of 6kv applied.
Richard Hull
X-rays are the first major radiation to issue from the working fusor and continues to get worse as the applied voltage rises.
Most amateur fusor demo models never produce a single x-ray and are therefore pretty benign in this area.
A deuterium filled fusor operated above 10kv will not only start to produce neutrons, but x-rays as well.
It is rather difficult to get a serious neutron flux from any amateur fusor operated under 30kv. Thus, the neutron hazard from short period runs in fusors up to 30kv is not a serious or immediate hazard.
X-rays, are another matter. They begin to spill out of viewports at about 12kv and the intensity grows to a dangerous level by 18kv. A geiger counter placed near a viewport at 20kv will usually saturate the entire counter and stop it from working, temporarily!!!
Ionization counters are best to sniff out x-rays and obtain a quantitative exposure. However we don't care about quantitative. We only care about detection. So most any low cost geiger counter will serve to alert us as to where x-rays are leaking out.
X-rays in the 15-30kv range are, for the most part, "soft" and are, therefore, considered "burning rays". They will be stopped totally in the first few millimeters of flesh and do maximum damage. (burn) by the same token they are easily stopped dead or shielded totally out of the picture. If you are not using your view port, cover it with a 1/16 inch thick sheet lead cover or a 1/4" thick aluminum disk. continuously sniff around this area with a geiger counter when the fusor is running to check for x-ray leaks at the edges.
Most of you will want to stuff a camera into the viewport and remote view the opertion on a video monitor. Make sure the area around the camera's lens and viewport is shielded to avoid scattered radiation.
Most metal fusors will have a lethal x-ray problem emerge when the entire shell becomes transparent above 70kv, but that is another issue and no one is likely to be there any time soon.
Remember, the eye is one of the most sensitive organs in the body to radiation. Never stare into a view port with high voltage in excess of 6kv applied.
Richard Hull