64 



RADIATION BIOLOGY 



Fig. 1-39. Fractions of the energy spent in different processes by an electron travers- 

 ing water as it slows down from 500 to 400 kev. The area not covered by cross 

 hatching corresponds approximately to the energy fraction which remains available 

 for further inelastic collisions by secondary electrons. (Courtesy M. Lewis.) 



3.5 



o 

 q: 



3.0 



2.5 



2.0 



1.5 



UJ 



o 



1.0 



q: 

 ill 



«^ 0.5 



0.3 



0.6 



2.4 



2.7 



3.0 



0.9 1.2 1.5 1.8 2.1 



PROTON ENERGY, Mev 

 Fig. 1-40. Fraction of total energy of protons penetrating water which is lost in (o) 

 ejecting K electrons of oxygen and (6) nuclear collisions for which la^E > 20 ev. 

 {Courtesy R. Platztnan.) 



