User:Brian P. Josey/Notebook/Junior Lab/2010/10/25: Difference between revisions

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Because she was sick the first week and I was sick the second, Kirstin and I will actually work from different data sets even though we worked together on the lab. So our individual data points will not be the same, but our end results should be very similar.  
Because she was sick the first week and I was sick the second, Kirstin and I will actually work from different data sets even though we worked together on the lab. So our individual data points will not be the same, but our end results should be very similar.


==Data Analysis==


==Conclusion==
==Acknowledgments and References==


==NOTE TO SELF==
==NOTE TO SELF==

Revision as of 10:37, 7 November 2010

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Poisson Distribution

This week, my lab partner, Kirstin, and I did the Poisson distribution experiment. This is a fairly straight forward experiment that is used to demonstrate the Poisson distribution. The Poisson distribution is used to describe when an event that occurs at random times independent of the last occurrence, but with an overall average rate. Examples of when this can be useful is counting the radiation off of a sample, or the number of births per day in a maternity ward. For this experiment, we counted the number of background radiation events in the lab. We used a combined scintillator-PMT to detect the events, and counted them using the UCS 30 software on the computer. From this, we were able to generate a series of data sets that contained the number of events in a given window of time, and then analyze them.

Equipment

Power Supply
Detector

Because most of this experiment was performed on the computer, there was very little equipment needed for the experiment. The first piece of equipment was the combined scintillator-PMT. We used this to detect the background radiation in the lab. When the scintillator absorbs radiation, it would fire a beam of ultraviolet light down the tube to the PMT. The PMT, then creates a signal voltage that is picked up by a card in the computer. The card then sends this information to the UCS 30 software, that then counts the number of radiation events in a given window of time. We also used a Spectech Universal Computer Spectrometer power supply to give a bias voltage to the detector. This voltage determines the sensitivity of the detector.

Set-Up and Procedure

The set-up was exceptionally simple:

  1. Turn on the computer and log-in if necessary,
  2. Turn on the Spechtech, it has to be turned on first before the software,
  3. Double click on the icon for the software on the desktop of the computer,

Like the set up, the procedure is pretty basic, the only issue is that the user interface on the computer doesn't make much sense. To set up the data collection, you want to set the cut off voltage fairly high before collecting the data. So the step by step process for collecting data is as follows:

  1. Under mode select "PHA (Amp In)"
  2. Under Settings Select "High Voltage On", and set it to an appropriate value, we used 1200 V. This value is used to adjust the sensitivity of the detector, and a higher voltage will decrease the sensitivity to only the most energetic radiation
  3. Under mode, select "MCS (Internal)"
  4. Under Settings, select MCS, and then pick your appropriate dwell time, which is how large each bin is for the number of events counted.
  5. To collect data, hit the green "Go button" and let it run its course
  6. When it stops, save it to a file or USB drive, but save it as a "comma separated variable (*.csv)"
  7. Import it into Google docs

From this point, the procedure is actually in the data analysis. We did every single dwell time between 10 ms and 1 second. The values for these are then, 10, 20, 40, 80, 100, 200, 400, 800 ms and 1 s.

Data and Results

Here is the data that I collected. Each spreadsheet contains all the individual data points per window on the first page, then the maximum and minimum values, number of windows with a given number of events, averages, and errors on the second page of each table. How I calculated this is described below in the data analysis section, but I included it on these tables for simplicity. The tables are arranged in increasing window size, starting at 10 ms, and concluding with 1 s at the bottom.

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Because she was sick the first week and I was sick the second, Kirstin and I will actually work from different data sets even though we worked together on the lab. So our individual data points will not be the same, but our end results should be very similar.

Data Analysis

Conclusion

Acknowledgments and References

NOTE TO SELF

Brian P. Josey 17:41, 25 October 2010 (EDT) Koch suggested that you could set up a random Poisson distribution on your computer to compare to the official data, as a way to compare with what we've done so far. It might be a good way to really learn the Poisson for your own good.