Effectiveness of Absorber as a Function of Location


Your goal in this experiment is to check the relative effectiveness of an absorber material placed between paddles or off to one side of the setup, as shown in the diagrams below.White boxes are paddles, black boxes are absorber material.



Horizontal detection













Vertical detection














As you can see, there are at least two ways of doing this experiment:one where the paddles are set to detect horizontally, and one where they are set to detect vertically.You may decide to test one or both of these situations.Before you begin, you should spend some time thinking about what results you might expect.It might be helpful to draw on the diagrams above as you do this.†† Using a ruler and a pencil, sketch the possible paths that muons might take as single-headed arrows.Remember that muons will pass easily through the paddles, but many of them will be stopped by the absorber.This means that



An effective absorber to use is lead, but any material available can be used. You should obtain enough lead (or whatever) so that you can make two bundles about 10 cm thick, though this is also variable depending on what is available. If you are testing in the horizontal detection setup, you can C-clamp pieces of absorber together so they will stand on edge in a fairly stable way. You should secure the detectors, so that you will not change their separation as you try the various configurations. Perform coincidence runs with no absorber, and with the absorber in as many different positions as you would like to test (to either side, on both sides, between, above, below, etc.).



Calculate the muon rate for each of the arrangements and the uncertainty in these values of count rate. To find the uncertainty, just divide the square root of the number of counts obtained by the time you counted.Find the percent reduction (Assuming there was one!) for each of the experimental runs as compared to the control (absorberless) one by subtracting the count rate with the absorber from the rate without and dividing this difference by the unabsorbed count rate, then, of course, multiplying by 100.


Compare your results in the different positions.Look for patterns.Discuss your findings with others.


Donít be surprised if you are surprised. There may be more going on here than first suspected. If the behavior is not as you first suspected what reasons can you think of that might cause departures? What ways can you think of to test those reasons?