Final Report:

From MariachiWiki

                                     Direction of Cosmic Rays: Experiment 1

Introduction

Cosmic rays are a form of radiation; they are high energy particles originating beyond the Earth during cosmological events. Cosmic rays were discovered by Victor Hess in 1912; at this point in time, the study of radioactive materials was of great interest, since very little was known about the structure of the atom. Electrometers, which consist of two thin ribbons of metal suspended in a vacuum bulb, which diverge when charge is present, were used in that period, and were able to measure only a very small amount of electric flux. Fortunately, more high-tech radiation detectors have been invented since then.

Scintillators are detectors that absorb high energy electromagnetic or charged particle radiation. A scintillator converts the energy it absorbs into light of a wavelength which can be detected by inexpensive or easy to handle detectors such as photomultiplier tubes. In our experiment, we used scintillators in order to determine from which direction the greatest amount of cosmic particles come from, (above, side, below, etc.). By strategically placing two scintillators in different positions in the classroom, we were able to effectively resolve at which angle the greatest amount of cosmic rays hits the Earth.

Procedure

• Use octagon-apparatus to hold the scintillators in place; use two scintillators at a time.

• Place one scintillator in the top slot, and one in the bottom slot; this has the advantage of putting a distance, d, between them, which controls for rays that come at an angle.

• Rotate octagon-apparatus. Perform three trials for each position, (scintillators at 0, 45, and 90 degrees), over two minute intervals.

• Graph the number of double counts, (counts that go through both scintillators), vs. their position.

We had to perform a second experiment. From our data, (see below for link), we determined that the greatest amount of cosmic rays either came from above or below. We used this second procedure in order to distinguish between the two options:

• We hooked up two scintillators, one above the other, putting as much space as we could between them using a lift, in an attempt to control for the direction of the rays.

• We hooked up a long cord to one scintillator, and a short cord to the other, and fed the lines to an oscilloscope after being put through an amplifier; we did this, anticipating that the signal coming from the scintillator with the longer cord would take longer to reach the oscilloscope than the signal coming from the other scintillator. The theory was that if signal one (with the longer cord) arrived before signal two or right on top of the signal, we'd know that the ray passed through scintillator one first.










Data/Results

First Procedure:

Here, you can see the all of the data we gathered, as well as the calculated average rate and accuracy.

Here, you can see a graph of the average rate of rays that passed through both scintillators per second vs. the position of the scintillators.

From our data it can be concluded that as the angle increases, the average rate decreases. Therefore, it is safe to say that most cosmic rays come from above or below.

Second procedure:

Below are Graphs 1 & 2. The blue line represents the signal from the top scintillator, the yellow line represents the signal from the bottom scintillator, and the green line is the signal coming from both (coincidence).

Graph 1:

Graph 2:

As you can see from the Voltage vs. Time graphs, the signal from the top scintillator always arrived first. When they were a smaller distance apart from each other, it was slightly hard to tell which signal came first, but when they are farther distance apart, it was easy to see that the ray passed through the top scintillator first. From this experiment, it can be concluded that most cosmic rays come from above.

Conclusion

During this experiment, we were able to determine that the greatest amount of cosmic rays actually come from above by strategically placing the scintillators in such a way that we could gather accurate data. Though there might have been some error, since we used a different length of cord for each scintillator, (it would have taken longer for a signal from a scintillator to reach the oscilloscope with a longer cord), the graphs from procedure two show without a doubt that the signal came through the topmost scintillator first. We were also able to prove that there is a direct relationship between the position of the scintillatos and the rate of cosmic rays that passed through the scintillator over time. Overall, the experiment was a success.

                                      Day and Night: Experiment 2

Introduction

Cosmic rays are constantly showering onto the earth. Given this fact then, are there more cosmic rays hitting the earth at different times of day? An experiment was done by taking two scintillators and putting them on top of each other.

Procedure

At first, it was decided that four scintillators should lie side by side in order to increase the surface area with the intention to gather a large amount of data. Yet a problem was found with this idea. The scintillators are not only able to detect cosmic rays; they also detect noise as well. Therefore, it was decided that the scintillators should be placed on top of each other to gather the largest number of coincidence counts of cosmic rays.

Data was taken over an interval of 2 minutes for five trials for two days. Cosmic ray counts were recorded at 9 AM, 12PM, and 9 PM. After analyzing the data by graphing the rate and its accuracy, no information was deduced due to the huge error bars.














Data

There seems to be a direct relationship between the number of rays and the time of day; cosmic rays seem to be in greater abundance at night. This is opposite to our original hypothesis. We should probably do more research on this topic, as well as take more data.

Results/ Error Analysis

When the graph was analyzed, it was determined that a trend line could be placed showing an increase of cosmic rays from morning to night, or the trend line could show a decrease of cosmic rays from morning to night.

Our error bars were so huge that our results were inconclusive. We could probably reduce the error by performing more experiments, for longer hours, for more days, and plotting the data points right on top of each other, until a definite trend could be seen.

Conclusion

From the data taken, it is concluded that more data should be taken by increasing the number of days as well as the hours per day. Cosmic ray detection data should be taken at every hour. Given this, the results should show us a better representation of whether the time of day affects the amount of cosmic rays.