Calibration of Radium 226 Introduction to Radium Discovered

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 1900 s – 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

Ra 226 Decay Chain

alpha yield isotope a 1 1. 90× 10 -08 3. 72 a 1 7. 92× 10 -07 4. 644 83 -BISMUTH-210 a 2 5. 28× 10 -07 4. 683 83 -BISMUTH-212 a 1 5. 25× 10 -07 4. 941 83 -BISMUTH-214 a 2 4. 41× 10 -07 5. 024 83 -BISMUTH-216 a 3 1. 28× 10 -06 5. 185 83 -BISMUTH-218 a 4 1. 22× 10 -05 5. 273 83 -BISMUTH-220 a 5 1. 13× 10 -04 5. 452 83 -BISMUTH-222 a 6 8. 23× 10 -05 5. 516 83 -BISMUTH-224 a 1 1. 22× 10 -05 4. 517 84 -POLONIUM-210 5. 304 84 -POLONIUM-212 a 2 Natural Radioactive Series energy 1 82 -LEAD-210 a 1 6. 00× 10 -07 6. 61 84 -POLONIUM-214 a 2 1. 04× 10 -04 6. 902 84 -POLONIUM-216 a 1 1. 10× 10 -05 5. 181 84 -POLONIUM-218 a 3 1 7. 687 84 -POLONIUM-218 a 2 1 6. 002 84 -POLONIUM-220 a 1 5. 00× 10 -06 4. 826 86 -RADON-222 a 2 7. 80× 10 -04 4. 986 86 -RADON-224 a 3 9. 99× 10 -01 5. 489 86 -RADON-226 a 1 2. 70× 10 -06 4. 16 88 -RADIUM-226 a 2 1. 00× 10 -05 4. 191 88 -RADIUM-228 a 3 6. 50× 10 -05 4. 34 88 -RADIUM-230 a 4 5. 55× 10 -02 4. 601 88 -RADIUM-232 a 5 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 18 ke. V 16 ke. V 10 ke. V 13 ke. V 15 ke. V

Ra-1 Shifted with Gold

Ra-1 Spectrum with Am 241 Peak

Centroid vs. Edge Energies 4. 784 Me. V Ra 234 5. 489 Me. V Rn 226 5. 304 Me. V Po 212 4. 601 Me. V Ra 232 6. 002 Me. V Po 220 7. 687 Me. V Po 218

5. 304 Me. V 4. 784 Me. V 6. 002 Me. V 5. 489 Me. V 4. 601 Me. V 7. 687 Me. V

Centroid energies vs channel number

Based on new calibration

Re-Calibrated Radium 2 Source New in blue old in red Blue 2006 calibration Red 1972 calibration 4. 91 Me. V 4. 696 Me. V 4. 22 Me. V 3. 997 Me. V 5. 48 Me. V 5. 307 Me. V 7. 044 Me. V

• http: //www. epa. gov/radiation/radionuclides/radium. htm • http: //www. physics. umd. edu/lecdem/honr 228 q/notes/U 238 scheme. gif • http: //www. eserc. stonybrook. edu/Project. Java/Radiation/index. html