Gamma absorption coefficient

In the case of photoelectric effect, assumption (1) is valid. For pair production, however, it is questionable because only the ener r - 1.022 MeV is given to the electron-positron pair. The rest of the energy, equal to 1.022 MeV, is taken by the two annihilation gammas, and it may not be deposited in the medium. There are cases when Eq. 4.65 is modified to account for this effect. Gamma absorption coefficients, as defined by Eq. 4.65, are given in App. D. 

Note that the only difference between energy and dose buildup factors is the type of gamma absorption coefficient used. For energy deposition, one uses the absorption coefficient for the medium in which energy deposition is calculated for dose calculations, one uses the absorption coefficient in tissue. 

Values of jl, the Gamma Absorption Coefficient, for Various Reactor Coolants as a Function of Energy... 

We have limited our investigations to the action of gamma-rays and fast neutrons on aromatic, alicyclic, aliphatic, and ionic compounds. The absorption coefficients for these types of radiation have an order of magnitude of lO /cm which is particularly adequate. Shallow penetrating radiations would only alter the superficial layers and would obviously not be able to affect the intensity of the quadrupole line substantially. This is for instance the case for ultraviolet light which has been shown to be unable to produce any effect on the resonance line of iodoform (CHI3 3Sg)... 

Storm, E., Gilbert, E., Israel, H. In Gamma-Ray Absorption Coefficients for Elements 1 Through 100, Los Alamos Scientific Laboratory LA-2237. University of California, New Mexico (1958)... 

Absorption Coefficient—Fractional absorption of the energy of an unscattered beam of x- or gamma-radiation per unit thickness (linear absorption coefficient), per unit mass (mass absorption coefficient), or per atom (atomic absorption coefficient) of absorber, due to transfer of energy to the absorber. The total absorption coefficient is the sum of individual energy absorption processes (see Compton Effect, Photoelectric Effect, and Pair Production). 

Absorption Coefficient, Linear—A factor expressing the fraction of a beam of x- or gamma radiation absorbed in a unit thickness of material. In the expression I=I0e+l x, I0 is the initial intensity, I the intensity of the beam after passage through a thickness of the material x, and p is the linear absorption coefficient. 

Irradiation Conditions and Dosimetry. All irradiations were carried out in the gamma-radiation field of either a nominally 10 or 18 kilocurie cobalt-60 source. Dosimetry of the gamma-radiation field was carried out using the Fricke method (ASTM test D 1671-59). Since the effective mass absorption coefficient for y-rays of this energy is nearly equal for the polymer and for the dosimetric solution, no correction was made for the change in media. 

Beta radiation has a finite range, whereas in theory x- and gamma rays are exponentially attenuated. It should be noted that x-radiation of each energy exhibits sharp changes in absorption coefficients for certain absorbers. 

Fig. 5.11. Linear absorption coefficients vs. gamma-ray energy for Si and Ge (PE = photoelectric, C =...

Absorptions Coefficient in cm.2/gram in Water at the Gamma Energy... 

The first term in the bracket is the contribution from the primary gamma rays (1.17 and 1.33 Mev.) at the point P, r cm. from the point source and the last term is the contribution from the scattered gamma rays at the point P. d is the dose rate in rads per sec. r is the distance in water from the point isotropic 60Co source of C curies fit = 0.0632 cm."1 is the total linear absorption coefficient in water for 1.25 Mev. photons ... 

Answer Cs emits a 0.662-MeV gamma. The mass absorption coefficient for this photon in water is (App. D) 0.00327 m /kg. The total mass attenuation coefficient is 0.00862 m /kg. The energy deposited at a distance of 0.05 m from the source is (E =... 

Table D2 Mass Energy Absorption Coefficients in cm / for Gamma Rays ...

Application to Gamma Rays. One mrad = 1 mr as shown previously. One mrad absorbed in the tissue liberates 0.1 erg/g. The mass absorption coefficient p/p is 0.032 cm /g for tissue in the energy range of 0.07 to 2 Mev. Substituting these values in Eq. (10-3) gives... 

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