Calibration of Radium 226
Introduction to Radium
•
Discovered in 1898 by Marie Curie
•
Radium (chemical symbol Ra) is a naturally-occurring radioactive metal. Its
most common isotopes are radium-226, radium 224, and radium-228.
Radium is a radionuclide formed by the decay of uranium and thorium in the
environment. It occurs at low levels in virtually all rock, soil, water, plants,
and animals.
•
Early 1900s – radium was used in such products as toothpaste, hair tonic,
ointments, elixirs, glow in the dark watch faces, and was an early source of
radiation treatment for cancer
•
Now is it used in some industrial radiography devices and added to the tips
of lightning rods, improving their effectiveness
Ra226 Decay Chain
alpha
yield
isotope
a1
1.90×10-08
3.72
a1
7.92×10-07
4.644
83-BISMUTH-210
a2
5.28×10-07
4.683
83-BISMUTH-212
a1
5.25×10-07
4.941
83-BISMUTH-214
a2
4.41×10-07
5.024
83-BISMUTH-216
a3
1.28×10-06
5.185
83-BISMUTH-218
a4
1.22×10-05
5.273
83-BISMUTH-220
a5
1.13×10-04
5.452
83-BISMUTH-222
a6
8.23×10-05
5.516
83-BISMUTH-224
a1
1.22×10-05
4.517
84-POLONIUM-210
5.304
84-POLONIUM-212
a2
Natural Radioactive Series
energy
1
82-LEAD-210
a1
6.00×10-07
6.61
84-POLONIUM-214
a2
1.04×10-04
6.902
84-POLONIUM-216
a1
1.10×10-05
5.181
84-POLONIUM-218
a3
1
7.687
84-POLONIUM-218
a2
1
6.002
84-POLONIUM-220
a1
5.00×10-06
4.826
86-RADON-222
a2
7.80×10-04
4.986
86-RADON-224
a3
9.99×10-01
5.489
86-RADON-226
a1
2.70×10-06
4.16
88-RADIUM-226
a2
1.00×10-05
4.191
88-RADIUM-228
a3
6.50×10-05
4.34
88-RADIUM-230
a4
5.55×10-02
4.601
88-RADIUM-232
a5
9.44×10-01
4.784
88-RADIUM-234
Purpose
• To re-calibrate the radium-2 source and
determine the correct energies for the alpha
particles being emitted
“DOG” Calibration
•
Layer of dirt, oil, and grease on the radium 1 source caused a downshift in energy
800
18 keV
15 keV
16 keV
10 keV
700
600
Counts
500
13 keV
400
Dirty
Clean
300
200
100
0
4.3
4.8
5.3
5.8
6.3
Energy
6.8
7.3
Ra-1 Shifted with Gold
Shifted Radium
Exp .036
Trim .030
20000
Exp .049
Trim .042
18000
Exp .038
Trim .033
Exp .045
Trim .039
16000
Counts
14000
12000
Exp .051
Trim .040
10000
Ra-1 w/ gold
Ra-1
8000
6000
4000
2000
0
4
4.5
5
5.5
6
Energy Mev
6.5
7
7.5
8
Ra-1 Spectrum with Am241 Peak
50000
45000
40000
Counts
35000
30000
Ra226-1
25000
Am241
20000
15000
10000
5000
0
4
4.5
5
5.5
6
Energy
6.5
7
7.5
8
Centroid vs. Edge Energies
Ra-1
4.784 MeV
Ra234
18000
5.489 MeV
Rn226
16000
7.687 MeV
Po218
6.002 MeV
Po220
14000
Counts
12000
5.304 MeV
Po212
10000
8000
6000
4.601 MeV
Ra232
4000
2000
0
4
4.5
5
5.5
6
Energy Mev
6.5
7
7.5
8
Radium 1 Spectrum
45000
5.304 MeV
40000
35000
4.784 MeV
Counts
30000
6.002 MeV
25000
7.687 MeV
5.489 MeV
20000
4.601 MeV
15000
10000
5000
0
4
4.5
5
5.5
6
Energy
6.5
7
7.5
8
Centroid energies vs channel number
Ra 1
8
7.5
y = 0.0166x - 0.3079
7
Energy
6.5
6
5.5
5
4.5
4
250
300
350
400
Channel
450
500
Based on new calibration
Ra 2
7.5
7
y = 0.0166x - 0.307
6.5
Energy
6
5.5
5
4.5
4
3.5
3
200
250
300
350
Channel
400
450
500
Re-Calibrated Radium 2 Source
4.91 MeV Ra226 2 Spectrum
4.696 MeV
1000
4.22 MeV
3.997 MeV
900
7.04 MeV
7.044 MeV
5.48 MeV
5.307 MeV
800
Counts
700
600
500
400
300
200
100
0
3
3.5
4
4.5
5
5.5
Energy
6
6.5
7
7.5
8
•
http://www.epa.gov/radiation/radionuclides/radium.htm
•
http://www.physics.umd.edu/lecdem/honr228q/notes/U238scheme.gif
•
http://www.eserc.stonybrook.edu/ProjectJava/Radiation/index.html