. The basic aspects of radiation effects on living systems. Radiation -- Physiological effect. 14 SECONDARY ELECTRONS skew; for example, many more secondary electrons have an energy between 10 and 20 ev than between 210 and 220 ev, and still fewer have an energy between 410 and 420 ev. Therefore the location of the upper limit determines only the cut-off point of the far tail of the energy distribution. Compare Fig. 1. The shape of the energy distribution can be discussed qualitatively on the basis of the classification of the collisions of the primary particle into two classes, namely, "
. The basic aspects of radiation effects on living systems. Radiation -- Physiological effect. 14 SECONDARY ELECTRONS skew; for example, many more secondary electrons have an energy between 10 and 20 ev than between 210 and 220 ev, and still fewer have an energy between 410 and 420 ev. Therefore the location of the upper limit determines only the cut-off point of the far tail of the energy distribution. Compare Fig. 1. The shape of the energy distribution can be discussed qualitatively on the basis of the classification of the collisions of the primary particle into two classes, namely, "glancing" and "knock-on" collisions. This. (electrons) Fig. 1. Number of secondary electrons per unit energy, N{E), receiving total energy E from an incident ionizing particle, plotted against E. Note that every secondary must get at least the ionization energy, /, if it is to leave the atom. The great bulk of the energy transfers occur at low energy, and thus the position of the maximum energy transfer, iS'inax, which may vary greatly with type of incoming particle, has in spite of the great variation no large effect on the distribution of secondary energies. The shaded region locates the region important for total energy loss. classification has already been explained to you by Morrison. Glancing collisions are much (about 8-10 times) more frequent than knock-on collisions in typical cases. One may wish to characterize the shape of the energy distribution by its slope n on a logarithmic plot, that is by assuming a distribution law of the type N(E) dE = dE/E'^. Now, if there were only glancing col- lisions, the slope n would be roughly If there were only knock-on collisions, n would be equal to 2. Therefore the glancing collisions, even though by far the most frequent, are much more unlikely to produce high-energy secondaries than the knock-on collisions [(1), pp. 515^.]. Low-energy secondaries, say up to 50-100 ev, are due overwhelmingly to glancing collis
Size: 2394px × 1044px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiv, bookpublishernewyorkwiley
