FINAL REPORT
From MariachiWiki
Cosmic ray particles are material that originate somewhere within the universe and travel through the vacuum of space. They are so small they generally can move through any substance without much difficulty. These particles can be detected by scintillators. The signal is then picked up by a tube which amplifies the signal and sends it to an oscilloscope or computer. By using two of these detectors, the level of noise detected can be decreased. The reason for this phenomenon is due to the fact that if there is a particle detected at the same time by the two detectors then the chances that it was actually a cosmic ray particle is extremely high. Using three detectors would decrease the level of noise even further. Another variable that can be changed is the voltage that the tubes within the detectors can utilize. However, as the voltage is increased the noise levels also increase as well, so there is a tradeoff between the efficiency and noise level as demonstrated by this graph.
Cosmic ray particles have various sources. Low energy particles usually come from the sun and are very frequent due to the fact that the sun is relatively close to the earth. Also compared to other sources of energy, the sun produces a small amount. The higher energy particles come from high energy sources such as supernovae. As for the highest energy level particles, their source is a mystery to researchers. As part of our research in Mariachi Laboratory, we were concerned with the properties of comic ray particles. We were specifically curious about two different factors: the relative direction the particles come from and the speed in which they move. By finding out these different properties, it is believed that a great deal can be learned about the composition and properties of the universe. This is important to understand so that human kind can better explain incidents that occur here on earth, as well as, properties of the earth itself. For the first experiment, we tested the effect of the distance between the detectors in comparison to the rate at which the particles were detected. Our prediction was that as the distance increased then the rate of detection will decrease. We used two detectors, a ruler, and a specialized computer program to calculate the number of coincidence at several distances. We obtained the following results.
It appears to have an exponential relationship. To test this hypothesis, the distance was graphed compared to the natural log of the rate.
There is no doubt that this shows a trend. Even though some of the error bars tend to overlap, the highest and lowest values do not, and a clear linear trend can be seen. So as a result the distance between detectors and particle detection rate has an exponential trend in which as distance increases, the rate decreases. The explanation for this is that fewer coincidences can be detected at the larger distances.
When they are close together then there is a wide variety of angles that the particles can hit the detector. However, as the detectors move farther apart then there is less of an angle that that the particles can hit the detector and still be detected by both. This leads to the conclusion that particles do not hit the surface of the earth at ninety degree angles, but actually they hit the earth at an infinite number of different angles.
For our second experiment, we tried to figure out the velocity of the particles. We used two detectors again and observed the difference in time between the detection of a particle. For the first trial we used the oscilloscope and for the second we used a computer program. We obtained data from two points. This was when the detectors were a distance of zero meters from each other and the second time was when the detectors were a distance of 2.6 meters.
These are our results.
The slope of the graph tells us the velocity of the particle. For the first trial we found the velocity to be 6.3 E8meters per second. This is amazingly the same magnitude as the speed of light; however it is also twice the speed of light. There is no possible way anything can be faster than the speed of light, so another trial was done with much more data. The velocity of the second trial came out to be 2.79 E8. This is extremely close to the speed of light, and the error shows that this result is very accurate. Also we could only measure the vertical component of the velocity and since not all particles move perpendicular to the scintillators, the velocity will naturally be smaller than the predicted value. Yet, it is safe to say that cosmic ray particles do move at the speed of light.
