A
NALYSIS
Compare your results for different types of radiation and different types of shielding.
Be careful with your logic since there are a lot of materials, radiation types, and
distances.
To be able to reach any conclusion make sure that only one quantity changes
at a time.
Be sure to take the statistical uncertainty in your data into account.
If you graph your
data (regardless of whether you used a spreadsheet), don’t forget to add error bars!
C
ONCLUSION
Does your data support your prediction?
Why or why not?
Does your data support the assertion that the position of a radiation shield has no effect
on the count rate? If there is an effect, how does it depend on the type of incident
radiation?
Does your data allow you to make any firm statements about whether
scattering or particle production occurs for each type of radiation?
196
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PROBLEM #3: SHIELD THICKNESS
You are working for a company interested in irradiating turkeys for longterm storage.
The management has asked your team for preliminary estimates of the minimum dose
of the radiation necessary to kill enough of the microorganisms to retard spoilage.
You
quickly realize that the radiation dose to be determined is the minimum necessary at
the center of the turkey.
Of course, turkeys come in different sizes so your first task is
to calculate how the radiation dose varies with depth inside the turkey. Your team
decides to test your calculation in the lab by modeling the turkey with sheets of
shielding material, as they are easier to handle than slabs of raw turkey meat.
Since the
company has not decided between using beta or gamma radiation for the process, you
will have to test your idea on both types of radiation.
Read Sternheim & Kane chapter 30 sections 30.130.3 & 30.9.
E
QUIPMENT
You have a Radiation Monitor (Geiger counter) connected to a LabPro Interface device
and the LoggerPro software. You will also have a shielding kit and different
radioactive sources: both a beta source, and a gamma source
If you need assistance, send an email to
[email protected]
.
Include the room
number and brief description of the problem.
W
ARM UP
1.
Draw a diagram with a source of radiation, a detector, and several identical sheets of
equal thickness material between them.
2.
Imagine that you measure the amount of radiation incident on the first sheet of
material and the fraction that passes through that sheet. The surviving radiation
now passes through a second sheet of material.
Based on your first set of
measurements, write an expression for the amount of radiation that passes through
the second sheet.
Continue this procedure for a third sheet.
You should be able to
continue for any number of sheets.
3.
Try some numbers.
Suppose that the initial radiation was 1000 particles and only
half of the incident particles pass through each sheet of material, calculate the
number of particles that survive the first sheet.
How many survive the second
sheet?
The third sheet?
On what quantity(ies) does the number of particles
surviving a sheet of material depend?
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 Fall '17
 Aaron Wynveen
 Physics

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