The Effect of Thorium
Note: Diagram not to scale.
Setup
In this experiment, the detector was run with the disc containing thorium in position and without the disc in position to test whether the presence of a radioactive substance affects the detector's results.
The detector was run in upper single mode with and without the disc and in coincidence with and without the disc. The detector was oriented horizontally in all trials. Each trial was run for 15 minutes.
Note: The error bar of the lower data point is covered by the data point's dot.
Results - Coincidence Mode
The graph shows a dramatic increase in the count rate when the disc containing thorium is in place.
This increase, however, does not actually signify that more cosmic particles are being detected.
What is happening is that the detector is misinterpreting the thorium radiation as cosmic particles!
Thus, when using the detector, it is important to remove all radioactive materials from the vicinity as they will affect the count rate without actually increasing the amount of cosmic particles going through the scintillators.
Note: The error bars of both data points are covered by their data points' dots.
Results - Upper Single Mode
The same results are shown when the upper single scintillator is used.
Even though the data collected without the disc containing thorium in place is drastically affected by phototube noise, this source of systemic error applies to all trials involving the use of a single given scintillator.
Thus, when the effect of the disc containing thorium was tested using the upper single scintillator, its natural effect was also affected by the same source of systemic error.
Since this factor is constant, it can be determined that the increase in count rate caused by the disc is not an extraneous measurement caused by a source of error.