1. 3/2003 Rev 1 II.1.1 – slide 1 of 30 IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources Session II.1.1 Part IIQuantities and Measurements Module 1Quantities and Units Session 1Radiometric Quantities & Interaction Coefficients

2. 3/2003 Rev 1 II.1.1 – slide 2 of 30 Introduction  Radiometric quantities and interaction coefficients will be discussed  Students will learn about radiation fields, fluence (rate), energy fluence (rate), fluence differential in energy, cross section, mass attenuation coefficient, and mass stopping power

3. 3/2003 Rev 1 II.1.1 – slide 3 of 30 Content  Radiation field  Fluence (rate)  Energy fluence (rate)  Fluence differential in energy  Cross section and example curves  Linear attenuation coefficient  Mass attenuation coefficient  Mass stopping power

4. 3/2003 Rev 1 II.1.1 – slide 4 of 30 Overview  Various radiometric quantities will be introduced and defined  Associated concepts such as interaction coefficients (for example attenuation coefficients and cross section) will be discussed

5. 3/2003 Rev 1 II.1.1 – slide 5 of 30 Radiation Field

6. 3/2003 Rev 1 II.1.1 – slide 6 of 30 Fluence Fluence, , is the number of particles incident on a sphere of cross-sectional area dA  = Unit: m -2 dNdA

7. 3/2003 Rev 1 II.1.1 – slide 7 of 30 Fluence Rate Fluence rate, , is the number of particles incident on a sphere of cross-sectional area dA per unit time  = Unit: m -2 s -1 dddd dt dt

8. 3/2003 Rev 1 II.1.1 – slide 8 of 30 Energy Fluence Energy Fluence, , is total energy carried by the “rays” striking a infinitesimal sphere of area dA  =  = whereR = EN, so  = E  Unit: J m -2 dRdA

9. 3/2003 Rev 1 II.1.1 – slide 9 of 30 Energy Fluence Rate Energy Fluence rate is the total energy carried by particles striking an infinitesimal sphere of cross-sectional area dA per unit time Energy fluence rate = Energy fluence rate = Unit: J m -2 s -1 dddd dt dt

10. 3/2003 Rev 1 II.1.1 – slide 10 of 30 Fluence Differential In Energy The fluence differential in energy  (E), or the distribution of fluence with respect to energy:  (E) = where d  is the fluence of particles with energy between E and E + dE dddd dt dt

11. 3/2003 Rev 1 II.1.1 – slide 11 of 30 Cross Section where  = cross section R = number of reactions per unit time per nucleus I = number of incident particles per unit time per unit area  = RI

12. 3/2003 Rev 1 II.1.1 – slide 12 of 30 Cross Sections for Neutron Capture in Uranium

13. 3/2003 Rev 1 II.1.1 – slide 13 of 30 Fusion Reaction Cross Sections

14. 3/2003 Rev 1 II.1.1 – slide 14 of 30 Cross Sections for Photon Capture by Deuterons

15. 3/2003 Rev 1 II.1.1 – slide 15 of 30 There are two types of attenuation coefficients:  Linear Attenuation Coefficient (LAC) provides a measure of the fractional attenuation per unit length of material traversed  Mass Attenuation Coefficient (MAC) provides a measure of the fractional attenuation per unit mass of material encountered Attenuation Coefficients

16. 3/2003 Rev 1 II.1.1 – slide 16 of 30  and HVL are functions of the energy of the photon radiation and the material through which it passes I = I o e (-  x) when x = HVL, then I = (½)I o (½)I o = I o e (-  HVL) ½ = e (-  HVL) ln(½) = ln(e (-  HVL) ) ln(½) = (-  HVL) ln(2) = (  HVL) ln(2)HVL Linear Attenuation Coefficient LAC =  M,E = ln 2 HVL M,E = 

17. 3/2003 Rev 1 II.1.1 – slide 17 of 30 LAC = MAC x density Mass Attenuation Coefficient 1 = cm 2 x g 1 = cm 2 x g cm g cm 3 The relationship between LAC and MAC is:   = x 

18. 3/2003 Rev 1 II.1.1 – slide 18 of 30  The amount of energy deposited will be the sum of energy deposited from hard and soft collisions  The “stopping power,” S, is the sum of energy deposited for soft and hard collisions  Most of the energy deposited will be from soft collisions since it is less likely that a particle will interact with the nucleus Stopping Power

19. 3/2003 Rev 1 II.1.1 – slide 19 of 30  The stopping power is a function of the charge of the particle, the energy of the particle, and the material in which the charged particle interacts Stopping Power

20. 3/2003 Rev 1 II.1.1 – slide 20 of 30  Stopping power has units of MeV/cm – the amount of energy deposited per centimeter of material as a charged particle traverses the material  It is the sum of energy deposited for both hard and soft collisions. S = = + S = = + Stopping Power dEdx Tot dE s dx dE h dx

21. 3/2003 Rev 1 II.1.1 – slide 21 of 30 Mass Stopping Power  Often the stopping power is divided by the density of the material,   This is called the “mass stopping power”  The dimensions for mass stopping power are MeV – cm 2 g

22. 3/2003 Rev 1 II.1.1 – slide 22 of 30 Mass Stopping Power m 0 c 2 is the rest mass of the charged particle in MeV 3727 MeV for an alpha particle and 0.511 MeV for an electron or beta particle 0.511 MeV for an electron or beta particle S  = (0.3071) Zz 2 A2A2A2A2 13.8373 + ln -  2 – ln I 2222 (1-  ) 2 moc2moc2moc2moc2 E 1 + 1 2 1 - ½  = = = =

23. 3/2003 Rev 1 II.1.1 – slide 23 of 30 Stopping Power  Z = atomic number  z = charge of the particle (  = 2,  = 1)  m 0 = rest mass of the particulate radiation  c = speed of light (3 x 10 10 cm/s)  I = the mean excitation potential of an atom of the absorbing material (2.16 x 10 -11 ) (Z)

24. 3/2003 Rev 1 II.1.1 – slide 24 of 30 Stopping Power Stopping power is used to determine dose from charged particles by the relationship: D =  in units of MeV/g, where  =the particle fluence, the number of particles striking an object over a specified time interval dE  dx

25. 3/2003 Rev 1 II.1.1 – slide 25 of 30 Stopping Power Converting this to units of dose results in the relationship: D =  (1.6 x 10 -10 ) Gy dE  dx

26. 3/2003 Rev 1 II.1.1 – slide 26 of 30 Summary  Radiometric quantities and interaction coefficients were discussed  Students learned about a radiation field, fluence (rate), energy fluence (rate), fluence differential in energy, cross section, mass attenuation coefficient, and mass stopping power

27. 3/2003 Rev 1 II.1.1 – slide 27 of 30 Where to Get More Information  Cember, H., Introduction to Health Physics, 3 rd Edition, McGraw-Hill, New York (2000)  Firestone, R.B., Baglin, C.M., Frank-Chu, S.Y., Eds., Table of Isotopes (8 th Edition, 1999 update), Wiley, New York (1999)  International Atomic Energy Agency, The Safe Use of Radiation Sources, Training Course Series No. 6, IAEA, Vienna (1995)

28. 3/2003 Rev 1 II.1.1 – slide 28 of 30  Knoll, G.T., Radiation Detection and Measurement, 3 rd Edition, Wiley, New York (2000)  Attix, F.H., Introduction to Radiological Physics and Radiation Dosimetry, Wiley, New York (1986)  International Atomic Energy Agency, Determination of Absorbed Dose in Photon and Electron Beams, 2 nd Edition, Technical Reports Series No. 277, IAEA, Vienna (1997) Where to Get More Information

29. 3/2003 Rev 1 II.1.1 – slide 29 of 30  International Commission on Radiation Units and Measurements, Quantities and Units in Radiation Protection Dosimetry, Report No. 51, ICRU, Bethesda (1993)  International Commission on Radiation Units and Measurements, Fundamental Quantities and Units for Ionizing Radiation, Report No. 60, ICRU, Bethesda (1998)  Hine, G. J. and Brownell, G. L., (Ed. ), Radiation Dosimetry, Academic Press (New York, 1956) Where to Get More Information

30. 3/2003 Rev 1 II.1.1 – slide 30 of 30  Bevelacqua, Joseph J., Contemporary Health Physics, John Wiley & Sons, Inc. (New York, 1995)  International Commission on Radiological Protection, Data for Protection Against Ionizing Radiation from External Sources: Supplement to ICRP Publication 15. A Report of ICRP Committee 3, ICRP Publication 21, Pergamon Press (Oxford, 1973) Where to Get More Information