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Energy is lost by the incoming chargedparticle through a radiative mechanism Beta Particle - Bremsstrahlung Photon + + Nucleus 3.
High Voltage Power Supply Tungsten Filament Target Glass Envelope Tube Housing Cathode Anode Current 4.
5. X-Ray Production Electron X-Ray Target Nucleus Tungsten Cathode (-) Anode (+) X-Rays 6. Radiation Detection Gas Filled Detectors Air or Other Gas Incident Ionizing Radiation Electrical Current MeasuringDevice + - Cathode - Anode + + + + - - - + - Voltage Source 7. Radiation Detection Scintillation Detectors Incident Ionizing Radiation Sodium-Iodide Crystal Photocathode Optical Window - Pulse Measuring Device Light Photon Photomultiplier Tube Dynode Anode 8. Bremsstrahlung Radiation Incident Electron (E 1 ) X-ray Photons Energy = (E 1- E 2 ) Deflected Electron (E 2 ) (E 1> E 2 ) 9. X-ray Tube 10. Target
11. Production of X-rays
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An incident photon interacts with an orbital electron to produce a recoil electron and a scattered photon of energy less than the incident photon Before interaction After interaction - - - Incomingphoton Collides with electron - - - - Electron isejected from atom - Scattered Photon 14.
15. Radiation Protection Concepts
ALARA 16. Shielding 17. Radiation Protection Basics
18. Time
19. Distance
20. Shielding
21. Required Personal Protective Equipment (PPE) 22. Personnel Monitoring 23. Workplace Monitoring 24. Safe Work Habits 25. Proper Lab Bench Set Up
26. Use of high activity sealed sources to examine structural components such as beams or pipes 27.
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where I = Intensity (exposure rate) at position 1 and 2 and R = distance from source for position 1 and 2 Position 1 Position 2 (mrem/hr) (mrem/hr) Source 2 2 2 2 1 1 R I R I R 1 R 2 I 2 I 1 30.
31. Sample Calculation
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Regulatory Agencies 44. Ordering & Receipt of Radioactive Materials
45. Posting & Labeling Notices
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Total US average dose equivalent = 360 mrem/year Total exposure Man-made sources Radon Internal 11% Cosmic 8% Terrestrial 6% Man-Made 18% 55.0% Medical X-RaysNuclear Medicine 4% Consumer Products 3% Other 1% 11 49.
X =Q (charge) M (mass of air) 50.
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H = D Q 52.
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Quality Factor X and Gamma Rays Electrons and Muons Neutrons < 10 kev >10kev to 100 Kev > 100 kev to 2 Mev >2 Mev Protons > 30 Mev Alpha Particles 1 1 5 10 20 10 10 20 54.
Total Egyp average dose equivalent = 360 mrem/year Total exposure Man-made sources Radon Internal 11% Cosmic 8% Terrestrial 6% Man-Made 18% 55.0% Medical X-RaysNuclear Medicine 4% Consumer Products 3% Other 1% 11 55.
Total US average dose equivalent = 360 mrem/year Total exposure Man-made sources Radon Internal 11% Cosmic 8% Terrestrial 6% Man-Made 18% 55.0% Medical X-RaysNuclear Medicine 4% Consumer Products 3% Other 1% 11 56.
X =Q (charge) M (mass of air) 57.
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H = D Q 59.
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Quality Factor X and Gamma Rays Electrons and Muons Neutrons < 10 kev >10kev to 100 Kev > 100 kev to 2 Mev >2 Mev Protons > 30 Mev Alpha Particles 1 1 5 10 20 10 10 20 61. N(t 0 ),A (t 0 ) are the initial number of radionuclides and initial activity, respectively. The half lifet 1/2of a radionuclide is the time by which the number of radionuclides has reduced to 50%. This shows a direct correlation between half life and decay constant for each radionuclide. The lifetimerof a nucleus is defined by: Quite often the expression lifetime can be found for radionuclides. This means that after a period corresponding to the lifetime of a radioactive nucleus the initial abundance has decreased to 36.8% of its initial value, of a nucleus can be found! 62. 63. 64. Unit forexposureE is the Roentgen [R] which is defined by the ionization between EM-radiation and air. 1 Roentgen is the amount of EM-radiation which produces in 1 gram of air 2.58 10 -7C at normal temperature (22C) and pressure (760 Torr) conditions. Dosimetry Units Due to the interaction between radiation and material ionization occurs in the radiated material! (Energy transfer from the high energetic radiation photons or particles to atomic electrons.) The ionization can be used as measure for the amount of exposure which the material had to radiation. 1 R = 2.58 10 -4C/kg 65. When interacting with matter EM-radiation shows particle like behavior. The 'particles' are called photons. The energy of the photon and the frequency (or wavelength ) of the EM-radiation are determined by the Planck constant h: h=6.62 -34J s = 4.12 10 -21MeV s The photon energy for X-rays and -rays is in the eV to MeV range. 66. X-rays originate either from characteristic deexcitation processes in the atoms (K , K transitions) (Characteristic X-rays). The photon energy corresponds to the difference in binding energy of the electrons in the excited levels to the K-level. 67. X-rays also originate from energy loss of high energy charged particles (e.g. electrons) due to interaction with the atomic nucleus ( bremsstrahlung ) 68. Theexposure rateER (= ionization/time) can be related to theactivityA of a source (in units mCi) via : F is the exposure constant in units[ (R cm 2 ) / (h mCi) ] , and d is the distance between source and material in units [cm]. The exposure constant is characteristical for the radiation source: 69. The absorbed dose D of radiation in any kind of material depends on the typical ionization energy of the particular material. The absorbed dose is defined in terms of the absorbed radiation energy per massW 1P. It therefore clearly depends on the energy loss behavior of the various kinds of radiation. The unit for the absorbed dose is : 1 Gray=1Gy = 1 J/kg = 10 4erg/kg = 100 radThe average ionization energy for air isW 1P 34 eV/ion. With 1 eV = 1.6022 10 -19 J and the charge per ion is 1.6 10 -19 , this yields for the absorbed dose in air D for 1 R exposure of EM radiation: D=1 R 34 J/C=2.58 10 -4C/kg 34 J/C = 8.8 10 -3J/kg = 8.8 10 -3Gy = 0.88 rad 70. The average ionization energy depends critically on the material. 71. There is an empirical relation between the amount of ionization in air and the absorbed dose for a given photon energy and absorber (body tissue). The absorbed dose in rads per roentgen of exposure is known as theroentgen-to-rad conversion factor C C is approximately equal to one for soft body tissue in the energy range of diagnostic radiology. The increase for bone material is due to higher photoelectric absorption cross section for low energy photons. 72. Dose (rad) = Exposure (R) x R to Rad Conversion factor 73. 74. 75. Exposure, exposure rate and absorbed dose are independent of the nature of radiation. Biological damage depends mainly on the energy loss of the radiation to the body material. These energy losses differ considerably for the various kinds of radiation. To assess the biological effects of the different kind of radiations better, as new empirical unit thedose equivalent H is introduced: DOSE EQUIVALENT with the quality factor Q which depends strongly on the ionization power of the various kinds of radiation per path length. In first approximation Q Z of radiation particles, Q( , X, ) 1. As higher Q as higher the damage the radiation does! 76. 77. EFFECTIVE DOSE The various body organs have different response to radiation. To determine the specific sensitivity to radiation exposure a tissue specific organ weighting factorw T has been established to assign a particular organ or tissueT a certain exposure risk. The given weighting factors in the table imply for example that an equivalent dose of 1 mSv to the lung entails the same probability of damaging effects as an equivalent dose to the liver of (0.12/0.05) 1 mSv = 2.4 mSv The sum of the products of the equivalent dose to the organH Tand the weighting factorw T for each organ irradiated is called the effective doseH : Like H T , H is expressed in units Sv or rem!. 78. 79. 80. 81. or Natural Decay Law The rate of the decay process is determined by the activityA(number of decay processes per second) of the radioactive sample.The activity is proportional to the number of radioactive nuclei (radionuclide) is the decay constant! Differential equation forN(t)can be solved 82. 83. Thank You