10m 



* H 





'I 1 



. . .* s> 





Fig. 3. Photomicrographs of particle tracks in photographic emulsion. Magnifi- 

 cation X750. 



a. Short cm-ved tracks (arrows) of photoelectrons produced by low-energy photons 

 simulated by placing thin liver slice containing radioactive carbon on XTB emulsion. 

 The nuclei of the Uver cells may be used as a rough scale by which to gauge the range 

 and ion density of the beta particles. 



h. The dense, short, and straight Hne of ionization produced by alpha radiation is 

 demonstrated by the affected photographic grains (arrows). The tissue cells shown 

 (necessarily out of plane of focus of the emulsion) are of lung alveoli, and the nuclei 

 (dark oval bodies) give some idea of dimensions involved. 



c. This plate was exposed to a mixture of fast neutrons and gamma rays. The 

 photo micrograph is of the same magnification as a and h. The dark grains scattered 

 at random are due to ionizations of photoelectrons produced by gamma rays. A rela- 

 tively long ionization track of an energetic proton (produced by a neutron) is indi- 

 cated by the arrow. 



401 



