PS 253 Lecture Notes - Lecture 1: Embry–Riddle Aeronautical University, Standard Deviation, Strontium

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Published on 7 May 2020
School
Course
Professor
Radioactive Decay Process and Shielding Tests
Pakshal Shah, Dominic Perito, Hallie Jenkins, Audrey Buehler
PS 253, Section 01, Kaydian Quintero, Department of Physical Sciences,
Embry Riddle Aeronautical University, Daytona Beach, Florida
March 2020
In first part of the experiment, emissions from a sample of 8*1011 atoms
of Co-60 (Cobalt-60) are measured in short time intervals. The histogram
created from the 300 counts of data gives the value of mean and standard
deviation as 199 and 14 respectively. In the second part, lead (Pb) and
aluminum (Al) sheets are used to stop gamma rays and beta particles emitted
from Cobalt-60 and Strontium-90 (Sr-90) respectively.
Statement of Purpose
To measure the number of
emissions from a sample of 8*1011
atoms of Cobalt-60 (Co-60). To test
the efficacy of lead and aluminum
in stopping C0-60 gamma rays and
Sr-90 beta particles.
Experimental Method
To detect the emission, a Geiger-
Muller (GM) tube is used which
excites an electron of a neutral gas
atom using gamma rays. GM tube
is connected to Pasco interface and
pulse detector with voltage set to
450V. In order to obtain 300
counts, the emissions are recorded
for 25 minutes in total. At the end
of this part, a histogram is created
to obtain the mean and standard
deviation. For the second portion,
emissions from unshielded Co-60
are measured first. And then the
emissions are recorded with
2,3,4,6, and 8 sheets of Pb. It is
repeated one more time with a 10-
layer aluminum foil slide. The
same process is repeated for Sr-90
with first unshielded condition and
then 1 Pb sheet and 1, 2, 5, 10, 20,
25, and 30 layers of aluminum (Al)
foil slides. Since both Co-60 and
Sr-90 were tested with no
shielding, 1Pb sheet, and 1 10-layer
Al foil slide. The effectiveness of
lead and aluminum sheets are
obtained by comparing the number
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of emissions obtained with and
without shielding.
Results Part I
From the 300 data points, the
mean value and the standard
deviation of the Geiger Counts
(counts/sample) was found to be
199 and 14 respectively.
Analysis Part I
A Gaussian distribution
statistical model can be prepared
from the results obtained. The
standard deviation, or uncertainty
of the data points can be obtained
by the following formula:
R = 
R =  = 14.1
As per the expectations, 68%
of data should fall under R, while
95% of data should fall under 2R.
Results Part II
All lead sheets are measured
to have a thickness of (1.50.05)
mm. The 10-layer aluminum foil
slide has a thickness of
(0.0130.05) mm.
The mean values of the
number of decays obtained with
shielded and unshielded Cobalt-60
(Co-60) are as follows:
# of Lead
Plates
Total
Thickness
±.005 mm
(mm)
Mean
Baseline
511
1
1.5
580
2
3
504
3
4.5
453
4
6
396
6
9
323
8
12
260
10 Al Sheet
0.013
511
Table 1: Pb and Al shielding tests results on Co-60
The mean values of the
number of decays obtained with
shielded and unshielded Strontium-
90 (Sr-90) are as follows:
# of Al foil
slides
Total
thickness
±.005 mm
(mm)
Mean
Baseline
1272
1
0.013
1169
2
0.026
1208
5
0.065
1098
10
0.13
1039
20
0.26
930
25
0.325
866
30
0.39
773
1 Lead Sheet
1.5
23
Table 2: Pb and Al shielding tests results on Sr-90
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