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BASE - DePauw

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BASE Project
DePauw University
Ruizhe Ma, Mark Tolley,
Professor Brooks
BASE
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The Balloon Assisted Stratospheric
Experiments (BASE) project is operated under the
Physics and Astronomy Department at DePauw
University.
Presently, the program uses helium filled weather
balloons to carry scientific experiments into the
stratosphere.
The communications and support system was
purchased from StratoStar Systems of Upland,
Indiana.
BASE – Summer 2010
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Our project this summer aims to measure
cosmic activities in the atmosphere by
flying Geiger counters through the region of
the stratosphere where these particles are
produced.
-Inside a
Geiger counter
Cosmic Rays and Energetic Particles
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Cosmic rays are continually
bombarding the stratosphere and
produce energetic particles
Ionizing radiation: Beta particles
and Gamma rays
Geiger counters record the number
of particles detected
Ionizing Radiation and Secondary Particles
Reference: http://www.ams02.org/what-is-ams/tecnology/ecal/
Cosmic Rays and Energetic Particles
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Number of particles is positively
related to:
- density of air molecules
- intensity of cosmic rays
We expect to see the counts
increase first then decrease after a
critical altitude
Lead Shielding
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Lead shielding is a commonly used form of
protection from radiation such as beta
particles and gamma rays because of its
high total mass per area in the path of
radiation particles.
We have adopted this form of shielding to
our experiment. We expect a decrease in
counts due to the lead shielding.
Equipment
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Latex weather balloon
Parachute
GPS and Radio
Geiger counter
Tilt
Camera
anchored in styrofoam boxes
Geiger Counters
Geiger Counters
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attached to BASIC Stamp microprocessor
a simple 555 timer circuit processes the
raw information into readable data
Geiger Counters
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programmed to record the total
counts for every consecutive minute
or 30 seconds up to sixteen hours
shielded with different thickness of
lead
Data from BASE 41
- counts per minute against time
BASE 41 - March 18
1000
900
800
Counts per minute
700
Counter 1 - nonshielding
600
Counter 2 - 3 partial
wraps of lead
500
400
Counter 3 - 1 partial
wrap of lead
300
200
100
0
40
60
80
100
120
140
160
Data from BASE 42
- counts per minute against time
BASE 42 - April 29
800
700
Counts per minute
600
500
Counter 1 - nonshielding
400
Counter 2 - 2.3 mm lead
Counter 3 - 4.1 mm lead
300
200
100
0
60
80
100
120
140
160
180
Data from BASE 43
- counts per minute against time
BASE 43 - June 10th
4000
3500
Counts per minute
3000
2500
Counter 1 - 8.31 mm
2000
Counter 2 - Non-shielding
1500
1000
500
0
0
20
40
60
80
100
120
140
160
Data from BASE 43b
- counts per minute against time
BASE 43b – June 23rd
3500
3000
Counts per minute
2500
2000
Counter 1 - 8.31 mm
Counter 2 - Nonshielding
1500
Counter 3 - Nonshielding
1000
500
0
0
20
40
60
80
100
120
140
160
Data from BASE 44
- counts per minute against time
BASE 44 - June 30th
1600
1400
Counts per 30 seconds
1200
1000
Counter 1 - 8.31 mm
800
Counter 2 - Nonshielding
Counter 3 - Nonshielding
600
400
200
0
0
50
100
150
200
250
300
350
400
450
Data from BASE 45
- counts per minute against time
BASE 45 - July 6th
1800
1600
Counts per 30 seconds
1400
1200
Counter 1 - 2.9 mm tube
shield
1000
Counter 2 - 2.7 mm box
shield
800
Counter 3 - Nonshielding
600
400
200
0
0
50
100
150
200
250
300
350
400
450
Data Analysis
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“M” shape
Critical altitude
at the top of “M”,
known as the
Pfotzer maximum
800
700
600
Counts per minute
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Critical
Altitude
500
400
300
Burst
200
100
0
60
80
100
120 - April
140
BASE
42
29160
Data from BASE 43
- counts versus altitude
BASE 43 - Counts vs Altitude
35000
30000
Altitude (m)
25000
20000
15000
Non-shielding
10000
5000
0
0
500
1000
1500
2000
2500
Counts per minute
3000
3500
4000
Summary of Critical Altitudes
Critical Altitudes
76
•Average: 67.6 ± 2.2 k feet (68% significance)
•82.6% of our data are within one Standard Deviation
74
72
Kilo Feet
70
68
66
64
62
60
0
50
100
150
200
Calendar days (ddd)
250
300
350
Crossover Altitudes
3500
BASE 43b – June 23rd
Counts per minute
3000
BASE 43b – June 23rd
2500
2500
Counter 1 8.31 mm
2000
1500
2000
Counter 2 Nonshielding
500
Counter 1 - 8.31
mm
Counts per minute
1000
1500
0
20
70
120
Counter 2 Nonshielding
1000
Flights
Altitude
(Feet)
43
31k
43b
32k
44
39k
500
0
30
40
50
60
Data Analysis
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The “showering effect” of the lead shield
800
4000
700
3500
600
3000
500
Counter 1 nonshielding
400
Counter 2 - 2.3 2000
mm lead
300
BASE 43 - June 10th
Counts per minute
Counts per minute
BASE 42 - April 29
Counter 1 8.31 mm
2500
Counter 2 Nonshielding
Counter 3 - 4.1 1500
mm lead
200
1000
100
500
0
60
110
160
0
0
50
100
150
Ground Tests
Shield
Counts w/
Thickness Shielding
Counts
w/out
Percentage Percentage
Shielding
Decreased
per mm
1.64mm
27.64
31.67
12.71%
7.75%
2.69mm*
28.16
30.87
8.78%
3.26%
4.77mm
26.57
31.07
14.51%
3.04%
5.62mm*
25.90
30.87
16.09%
2.86%
8.31mm
25.47
31.37
18.81%
2.32%
*Had only one run
Ground Tests
Shield
Shield
Counts w/
Counts w/out
Percentage
Type
Thickness
Shielding
Shielding
Decreased
Tube
2.9 mm
26.22
34.19
23.29%
Box
2.7 mm
31.46
34.19
16.65%
Geometry of the Shower Effect
Geometry of the Shower Effect
Low
Energy
Case
High
Energy
Case
Geometry of the Shower Effect
Data from BASE 45
- counts per minute against time
BASE 45 - July 6th
1800
1600
Counts per 30 seconds
1400
1200
Counter 1 - 2.9 mm tube
shield
1000
Counter 2 - 2.7 mm box
shield
800
600
400
200
0
0
50
100
150
200
250
300
350
400
450
Data from BASE 42
- counts per minute against time
BASE 42 - April 29
800
700
Counts per minute
600
500
Counter 1 - nonshielding
400
Counter 2 - 2.3 mm lead
Counter 3 - 4.1 mm lead
300
200
100
0
60
80
100
120
140
160
180
Conclusions
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1. The number of energetic particles
increases as the altitude increases until a
critical altitude beyond which the counts
start to decrease. No seasonal variation has
been seen.
2. A lead shield of a given thickness can
only provide a protection from energetic
particles of up until a particular energy. If
the particles are too energetic there exists
the “showering effect” which increases the
number of energetic particles.
Conclusions
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3. The enclosed volume and the shield
thickness both affect counts. With the same
shield thickness, more volume enclosed by
the shield leads to more counts. With the
same enclosed volume, the thicker shield
leads to less counts on ground but higher
counts at high altitudes.
Further Work
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Try to find a quantitative
relationship between counts and the
enclosed volume/shield thickness
Floating valve
Hydrogen
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