NSCL Cosmic Ray Experiment

Originally a Word Document, PDF form: cosmic_directions.pdf

How the CRD Works | Operating the CRD | Experiment | Analysis

Analysis:

Graph with error bars
Figure 4   a chart with error bars for the
y-variable

In your table, you have recorded the number of cosmic rays that struck the detector in a three minute interval.  We are interested in how often an event occurs, so we calculate a count rate.  Divide the counts by 180 seconds to get the count rate and record it in the table.  Do this for each angle.  Next, record the error in your count rate.  The error is given by the following formula:

error equals the square root of the count divided by time
where σCR is the error in count rate,
N is the number of counts,
and t is the time (180 seconds).

 

 

Now that you have the count rates, plot them on a rough graph.  The x-axis should be the angles and the y-axis should be the count rate.  Make error bars for the count rate by drawing lines in the positive and negative y direction on each of your points.  The length of the each line should be the size of your error.  Then, answer the following questions.

  1. Does the curve look like any other graphs you’ve seen?  Sketch a continuation of the graph from 90˚ to 180˚.

 

 

  1. Are count rates higher for small angles or large angles? 

 

 

  1. From which direction are the cosmic rays coming most often?  Perpendicular to the earth, or parallel?

 

 

  1. Was your prediction correct?  Does the data support your hypothesis?

 

 

  1. Why do you suppose they would come from that direction?  Hint: what are the effects of the atmosphere?