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ANALYSISCompare 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! CONCLUSIONDoes 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 long-term 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 30.1-30.3 & 30.9. EQUIPMENTYou 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.WARM UP1.Draw a diagram with a source of radiation, a detector, and several identical sheets ofequal thickness material between them.2.Imagine that you measure the amount of radiation incident on the first sheet ofmaterial and the fraction that passes through that sheet. The surviving radiationnow passes through a second sheet of material. Based on your first set ofmeasurements, write an expression for the amount of radiation that passes throughthe second sheet. Continue this procedure for a third sheet. You should be able tocontinue for any number of sheets.3.Try some numbers. Suppose that the initial radiation was 1000 particles and onlyhalf of the incident particles pass through each sheet of material, calculate thenumber of particles that survive the first sheet. How many survive the secondsheet? The third sheet? On what quantity(ies) does the number of particlessurviving a sheet of material depend?
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