Radiation counting variability.

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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Frank Sanns
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Radiation counting variability.

Post by Frank Sanns »

Getting a good average count rate is not as trivial as it would seem. Taking too long a count rate can miss variability that is happen on a shorter time scale. Sampling for too shot a period and the result may not be representative of a longer counting time.

Of course the overall time of the count is really not really the critical factor. This seems counter intuitive. A longer count should give a better average with a smaller standard deviation. Excluding background, noise in the detector, efficiency of the detector, dead time, and everything else other than the source can reveal what is really going on.

What we are really doing is not counting radioactive emissions. We are not interested in neutrons or gamma ray counts.

We are actually counting time intervals. Time intervals between received ionizing radiation photons or neutrons, etc. Once you can see that the measurement is about the time interval between clicks, it is easy to see how variability plays out.

A low emitting source can have multiple seconds between clicks on the counter. It can also have two clicks falling seemingly at the same time. This is because of the variability of statistics of counting a small number of samples. There are ways to resolve this variability. One is to do a count time that is so very long that the long term average can be determined. Drift and changes to background may adversely affect that. Shorter counts can be stacked and that improves the signal to noise ratio and will take into account drift.

The simplest answer though is to just get more interval counts. Bring the source closer to the detector or increase the strength of the source. Both will give more statistical counts in a shorter period of time. After around 10,000 counts, the number will yield a good repeatable average.

Counting time is not the important factor. It is only how many statistical data points of the time intervals between clicks that there are.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Richard Hull
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Re: Radiation counting variability.

Post by Richard Hull »

The fusor, especially the spherical fusor has many fusion modalities. One may be dominant but there are many more modality fusions of a variable nature occurring at the same time.

Nuclear disintegration results from a single modality of a single nuclear atom with a specific half-life. The decay is statistical and exponential in nature. This will never change. The process is singular in nature and fixed. Therefore, counting and statistics here are easily dealt with.

Fusion is a quantum statistical driven thing. It is not exponential in its action. Nor will stable driving energy at a given cross section in a spherical fusor produce a stable fluence of neutrons. The spherical fusor is a device that does fusion by several different modalities with none of them producing stable fusion within a volume of fusible gas, even with fixed input energy, and fusion conditions operating at a fixed cross sectional point will be warranted to ever be a smooth fusion device. What's more, the various modalities can even interfere with each other especially in velocity space. Such modalities and interrelated interferences will vary moment to moment. Some precision count is possible only within an instant in time. Over long time intervals of even seconds to minutes wild variations in the number of fusions can be expected in a spherical fusor. (Continually shifting modality prominences and velocity space cross interferences within these modalities)

Spherical fusor fusion modalities suspected and most likely in play during operation.

Beam on target....
Wall fusions due to direct deuteron impact on wall loaded deuterium.
Wall fusions due to fast neutral impact on wall loaded deuterium.
Grid fusions based on fast deuteron impact on grid loaded deuterium.
Inner grid fusions due to fast deuteron mutual collisions (recirculation)

Velocity space fusions.... This is partially due to idealized deuteron production at the optimum large surface area of the sphere due to massive electron bombardment of the surface of the sphere popping out an ionized deuteron from surface buried deuterium. This allows a possible full acceleration of said wall created deuteron to the inner grid and recirculation and or collision through velocity space....

1. Mutual fast deuteron collisions
2. Fast deuteron fast neutral collisions
3. Fast deuteron slow neutral collisions
4. Fast deuteron slow deuteron collisions

Some of the above fusion events with emit neutrons isotropically, some will not, adding to varying neutron detector intercepts.

Thus, regardless of methodology of measurement, fusion within a larger (>5") spherical fusor will be in constant variation.

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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