will Attach 2 things below,
1- The lab manual, “For this report you only need submit the data analysis attached below and answers to the 6 questions”.
2- Nuclear radiation data
the lab should not be too long, 3-5 pages is okay.
The report should be done within 12 hours.
Temple university physics
At the surface of the Earth, we’re under constant bombardment from ionizing radiation from sources all around us such as naturally occurring radon gas and cosmic radiation. Ionizing radiation includes alpha, beta, and gamma particles and is contrasted with non-ionizing radiation such as visible light and thermal radiation. When we think about the dangers of radiation, in general it is the damage done to DNA by ionizing radiation that we are concerned about. The sources used in this lab have extremely low activity, so they are safe for use in the teaching lab.
In the following experiments, we’ll use a Geiger-Muller (G-M) particle counter to detect the particles emitted when various nuclei undergo radioactive decay. When a decay particle passes through the G-M counter, we get a pulse output which is counted by a simple electronic circuit.
Learning Goals for This Laboratory:
· Practice quantifying radiation using counts, rates, energy, and logarithmic relationships.
· Know what types of shielding will absorb beta, and gamma radiation.
· Understand how half-life is calculated and how counts change with time during exponential decay.
Part I. Counting Radiation over Time
The G-M counter logs ionizing radiation events vs. time. We will run a continuous data collection recording the number of counts in consecutive 5 second intervals.
Figure 1. G-M counter setup.
1. The counter rests above the sample as shown at right. Plug the G-M counter into the proper port on the interface and make a display of counts vs. time.
2. Adjust the height of the G-M counter and sample holder so that samples will sit 1 to 2 cm below the G-M counter. In Capstone at the bottom of the screen, set the sample rate of the G-M counter to 5 sec.
3. Click Record and let data collection run for 90 s.
4. Examine the data for counts over time. For the data section of your report, describe qualitatively how the counts for one interval compare to the next. For example, were any trends noticeable? How much variation was there across the data set? Is there noticeable decay over the course of the 90 seconds of data collection?
Question 1. Why aren’t the counts exactly the same for all of the 5-second intervals?
Part II. Radiation Shielding
Alpha, beta, and gamma particles interact with matter in different ways. Watch the video demonstration here to see how different types of shielding work for the different types of radiation.
Question 2. Watching the video, you notice that the beta source has much more activity than the alpha source. Why is it problematic to conclude that the nuclide in the beta source decays more readily than the nuclide in the alpha source? See Equation 1 below to help you answer.
1. Activity data was collected for different amounts and types of shielding for beta and gamma radiation.
2. Examine the data. What conclusions can be made assuming this data is reliable? Include these observations in the data section of your report. Be sure to comment on how the type and amount of shielding affected the detected radiation.
Question 3. Which type of radiation was most penetrating according to the data?
Part III. Radioactive Decay
The activity decreases with time because every time a radioactive nucleus decays, the is one fewer of the original radioactive nuclei remaining. The probability of a decay event occurring depends on the nucleus in question as well as the number of nuclei present. This allow us to derive the decay equation (see derivation in your text)
where is the number of nuclei remaining at time and is the decay constant for the particular radioactive element in question. The decay rate (a.k.a. activity) also follows the same functional form of exponential decay, so the data we are collecting in counts per minute can be directly fit to an exponential decay function. The sample in this experiment is barium-137m. It is a metastable isomer of barium with a half-life that is short enough to easily measure in the teaching lab.
1. The instructor will provide a sample of 137mBa for this experiment. The sample is very weakly radioactive; nevertheless, care should be taken in handling it. If you should come in contact with the liquid, wash your hands with soap and water. The experiment is time sensitive – you will get better data if you begin measuring the radioactivity as soon as possible after receiving the sample. To this end, make sure your setup is ready before you get the sample.
a. Have the Geiger counter positioned so that when you place the sample on the lab bench, it is within 1-2 cm from the Geiger counter.
b. Adjust the sample rate of the data collection to 5 seconds if it is not already. To capture the full decay, you will need to collect data for at least 10 minutes. Once you hit Record, the computer will generate a data point every 5 seconds.
2. Fit the exponential decay to an appropriate function and display the trendline equation on the graph.
3. Use your fit and refer to the equations from your text to find the decay constant and half-life from your data.
4. Also plot the natural log of the count rate vs. time.
Question 4. What is shape of the curve when plotting the natural log of the count rate?
Question 5. What is the meaning of the slope of the natural log of count rate vs. time?
5. Compare your value of the half-life to the established value for Ba-137m by calculating percent error.
Question 6. The average natural background radiation received for a person in the U.S. is about
3.5 x 10-5 rem per hour. (rem is a unit useful for radiation dosage).
Calculate how much radiation a person could receive in this lab if they held one of the 0.1 Ci Cs-137 sources in their closed fist for 1 hour and all of the radiation was absorbed (100 % efficiency). Assume the mass of the hand is 2 kg. The gamma radiation produced by Cs-137 is 662 keV (i.e. each decay releases a 662 keV photon). How does this compare with the average natural background radiation received in the same amount of time?
Use the following conversions to obtain your answer:
1 Ci = 3.70 X 1010 decays per second
1 eV = 1.6 X 10-19 J
1 J/kg = 100 rem (for gamma rays)
For your lab report: For this report you only need submit the data analysis and answers to the questions.
7/23/2020 2:43 PM