Ionizing radiation as a function of time

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
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Kuba Anglin
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Ionizing radiation as a function of time

Post by Kuba Anglin »

I recently finished editing the 5+ hours of raw video I had recorded constructing and operating the fusor into a 15-minute video. When I was editing, I decided to graph the Geiger counter data that was picked up by the camera. Here is the data:

Image

During this test the voltage in the reactor was stable (around 26 kV). This data clearly shows that the ionizing radiation produced by the reactor increases linearly with time. The first minute of operation is not included in the trend line as it represents the period where the digital counter was adjusting to the new radiation flux.

I understand that the fusor increases its rate of fusion as it runs due to deuteration of the chamber walls, but those few gamma rays shouldn't account for such a significant increase in ionizing radiation. Can someone explain this increase in ionizing radiation?

Thanks,
Kuba
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Richard Hull
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Re: Ionizing radiation as a function of time

Post by Richard Hull »

You have just learned how to apply for a job as an x-ray technician in the 20th century teens and early twenties!! Early cold cathode x-ray tubes relied on critical gas control and this control was the job of very specialized technicians. As the tube aged in use, it got "hard" (vacuum got better). This was very bad. A technican heated a palladium arm in the tube via bombardment and this outgassed the trapped gas molecules, softening the tube. (Decreasing the vacuum level) This restored the tube to operation at a fixed voltage of its supply.

Once the heated cathode appeared in the 1920's, (GE's "Coolidge tube"), and had a stable electron source, the x-ray tube could be made very, very hard with a deep vacuum and remain perfectly stable forever. X-ray Technicians lost their jobs and any untrained country doctor or nurse could work his x-ray system after a few days simple training.

You have effectively done this ancient artifice by working the vacuum either by running the pump, valving or burying and regassing the demo device. It seems you improved the demo system's operation as an x-ray tube quite unwittingly which is often the case in demo systems. You are learning via study and the doing. This is always the best way to learn and own concepts. You could have read this in a book and quickly forgotten it a few months ago......Now you own it.

A far more important graph would be one of current against vacuum level with increasing radiation. (this assumes not one quiver in the applied voltage)

Voltage current and vacuum are the keys to x-radiation from the fusor. In a real fusor, when run properly, as the voltage is brought up on a variac and long before you get a gas discharge, a GM counter will go nuts as the fusor is a cold cathode x-ray tube. Once the gas discharge occurs it is a fusor, doing fusion and is, still, an x-ray tube.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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